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Given the wide range of actuators and electronics which go into a robot, choosing the right battery may not be an easy task. This article guides you through the thought processes involved in choosing one or more batteries for your robot.

 NiMh Batteries LiPo Batteries Single Cell Batteries

Even if you are just starting in robotics, you may have already realized that the components you want to use don’t all operate at the same voltage. If you look at a production robot, you start to wonder “how is everything working off just one battery?”. There are two approaches taken, and we’ll help you determine which is best for you.

## Multiple Batteries

• Requires less design time
• Can be more efficient

• Various parts of the robot will stop working at different times
• Multiple batteries to recharge

How do you know if you need multiple batteries? Check the nominal voltage of each of the products you selected:

• Electronics (microcontroller,  motor controller power etc) usually operate at 9V-12V. Some operate at low as 3.3V and 5V.
• Actuators (DC gear motors, stepper motors, servos etc) usually operate at 6V to 12V. A few operate as low as 3V
• Sensors usually operate 5V

Based on the ranges above, it’s easy to see how, wen selecting optimal components for your project, that the voltage range may differ for each type of component. Fortunately most microcontrollers has a built-in voltage regulator which provides 5V to the I/O pins, so you don’t need a dedicated 5V battery. Should you choose a normal microcontroller, it’s likely that the voltage range is 9V  to 12V. Operating a normal hobby servo motor (rated at 4.8V to 6V) from a 9V to 12V battery would quickly burn it. What to do? The easiest option would be to use a smaller 12V battery for the microcontroller, and a larger 6V battery for the servos.

## One Battery

• One battery to charge
• Lighter weight

• (May) require voltage regulator
• A bit more complex to understand and wire

Continuing the example above, where we chose a 12V microcontroller and 4.8V to 6V hobby servos, we have the option of using one (larger) 6V battery pack and a step-up voltage regulator. A voltage regulator does exactly as the name implies; it regulates the voltage. In our case we would need one which can accept 6V input and step it up to 12V.

Choosing a lower motor voltage does not automatically mean the list of motors available to you will be low power. However, a high voltage motor (36V, 48V, 60V) tends to be reserved for large DC motors. The second approach is to first select the ideal motor and design your robot’s electronics system around the indicated nominal voltage. Both approaches have their advantages and disadvantages and it is up to you to choose which you prefer.

Voltage dividers allow you to power electromechanical devices at different voltages. Voltage dividers are purely electrical devices with no programming involved. If you do not want to use voltage dividers, most electronics operate at 5 to 9V, so choosing either 6 or 9V as your robot’s supply voltage is the best choice (never assume an electronic device operates at 6 or 9V: you always need to read the supply voltage specifications for each electronic component). The other option is to use two different power supplies: one for the motors and another (smaller one) for the electronics.

Should you wish to operate your robot at 9V, you can often still choose a 12V motor, though you must keep in mind the rpm will be less that that listed (estimated as a fraction of the nominal value) and the motor efficiency will be slightly reduced.

## Tips / Tricks

Standard battery voltages are:

• 1.2V: one rechargeable NiMh AA or AAA battery (unless you want a really small robot, one cell does not do much)
• 1.5V: one Alkaline AA or AAA battery(disadvantage of not being rechargeable and can’t do much on its own)
• 2.4v: two rechargeable AA or AAA batteries; still can’t do much on their own, even for small robots
• 3V: two alkaline AA or AAA batteries; most microcontrollers cannot operate at this voltage, let alone most actuators.
• 3.6V: three rechargeable NiMh AA or AAA batteries; this is usually the minimum voltage to run certain microcontrollers
• 3.7V: one LiPo battery; this is close enough to 3.6V and is the minimum to run certain microcontrollers
• 4.5V: three alkaline AA or AAA batteries… why even consider non-rechargeable in robotics?
• 4.8V: four AA or AAA together provide the minimum voltage to operate a standard hobby servo motor. These can be either as individual cells or as a single rechargeable battery pack.
• 6V: four AA or AAA alkaline batteries, five rechargeable NiMh cells or one 6V rechargeable lead acid pack; this is the maximum (and ideal) voltage most hobby servos can handle. Use these if your servos need a bit more power.
• 7.2V: six AA or AAA rechargeable NiMh batteries is perfect for 7.2V DC gear motors. These are usually in a battery pack rather than as individual cells and you will need a more specific NiMh battery pack charger.
• 7.4V: two LiPo cells can often power a microcontroller and works great for 7.2V DC gear motors. Unfortunately it’s too high for most hobby servo motors.
• 7.5V: five alkaline AA or AAA: almost never used because it’s simply too many single-use batteries.
• 8.4V: 7x NiMh AA batteries (hard to find chargers for 7xAAA NiMh batteries). This is also not used much because it means charging 7 batteries at the same time.
• 9V: 6x Alkaline batteries, one 9V (NiMh or Alkaline) battery or one 9V lead acid batteru: please avoid using 6x alkaline for the sake of the environment. A 9V single cell rectangular battery is often used to power the microcontroller in dual battery configurations. 9V lead acid batteries are a bit harder to find and although they are quite heavy, are fairly inexpensive and high capacity.
• 9.6V: 7x NiMh cells, usually in a battery pack configuration. This is good for motors which operate at 9V, and also for microcontrollers (most can operate above 9V).
• 11.1V: three LiPo batteries produces almost 12V and is much lighter than 10x 1.2V cells or a 12V lead acid battery pack. You need a specific LiPo charger capable of charging 3 cell LiPo packs.
• 12V: 10x 1.2V cells (always configured as one NiMh battery pack) or one 12V rechargeable lead acid battery pack. 12V is ideal for a variety of DC gear motors and most microcontrollers.
• Anything above 12V is usually reserved for very large robots. If you have a 14.4V LiPo or 18V NiMh pack from a cordless drill, keep in mind that finding motors which operate at these voltages is not easy.

Robots using servo motors (legged robots or robotic arms) tend to operate at 4.8V (4x AA NiMh cells) or 6V (5x NiMh AA cells). You can use a fairly inexpensive voltage regulator to power the microcontroller, increasing the voltage from 6V to 9V.

Small to medium mobile robots often use a 6V, 9V or 12V NiMh battery pack, the choice of which depends on the nominal voltage of the drive motors. If the robot includes one or more servo motors (for a pan/tilt for example), the microcontroller can usually provide enough current from a 5V digital pin. If your microcontroller operates at 9V and you want to use 6V motors, you might consider a two battery solution.

Medium sized mobile robots tend to use one 12V battery; lead acid or single NiMh battery pack (or an 11.1V LiPo battery if weight is an issue).  Large robots use 12V or 24V from one or more lead acid battery packs.

## Chemistry

NiMh: This is by far the most common type of battery used in mobile robots. NiMh batteries are rechargeable and their value (price / capacity / weight) is hard to beat. There is almost no memory effect, meaning every charge should bring the battery up to full capacity.

NiCd: These batteries are slowly disappearing because of their memory effect: if you don’t discharge the battery properly and then recharge it to full capacity, you lose part of the capacity each time.

Alkaline: These are the least expensive batteries in the short term, and provide a higher voltage than NiMh, but are not great for the environment, and you constantly need to buy replacements.

Lead Acid: Still the cheapest option for high capacity, lead acid is usually reserved for medium sized robots because of their incredibly high weight.

LiPo: These are fast becoming the most popular type of battery because of their light weight, high discharge rates and relatively good capacity, except the voltages increase in increments of 3.7V, so you need to plan to use LiPo before selecting your electronics and actuators.

## Nominal Voltage

A motor’s nominal voltage is the voltage at which the motor provides the best power output to efficiency ratio (rather than highest efficiency or highest power output). Operating a motor at the nominal voltage also helps to guarantee a long useful life.

## Capacity

A battery’s capacity determines roughly how long a battery will last at a specific voltage given a specific discharge rate. For example, if you choose a 12V, 2Ah (2000mAh) battery pack (regardless of chemistry), the battery should be able to run a 12V motor consuming 2A continuously for 1 hour. Alternatively, it can run a 12V motor consuming 1A for 2 hours, or a 12V motor consuming 0.5A for 4 hours. The rule of thumb is to divide the capacity (assuming you are running an actuator at the same voltage) by the actuator’s current under normal load to get the time the motor will last.

### Example 1

2x Drive Motors: 6V nominal, 1A each under normal load

1x 6V NiMh Battery Pack, 2200mAh (equivalent to 2.2Ah)

Note that the battery was chosen based on the motor’s nominal voltage.Should you instead operate 6V motors from a 7.2V battery, the calculations become more difficult (use the total watt-hours divided by the total watts per hour to get an idea).

Therefore the 6V battery pack will last:

2.2Ah battery / (2 motors x 1A per motor) = 1.1 hours

### Example 2

18 servos used for a hexapod robot which operate at 6V nominal and consume 250mA under normal load*

1x 6V NiMh battery pack at 5Ah.

First, we will assume that all motors are under load at all times (i.e. worst case scenario) and therefore all 18 will be consuming a total of 4.5A

5Ah battery / 4.5A = 1.1 hours

Note again that the battery was chosen based on the motor’s nominal voltage.

## Discharge Rate

The continuous discharge rate of a battery is very important because if you choose a battery that cannot discharge at the required current, the robot will either not work properly or not work at all.

### Example 1

You selected four 12V motors for your 4WD outdoor mobile robot. Each motor consumes 1A under normal load, and more in the case of a slope. You decide to choose a 12V, 2Ah NiMh battery pack, not caring about the continuous discharge rate. You discover that your robot stops when it encounters even the slightest obstacle or incline. Why? In this case operating all four motors consumes ~4A while an NiMh pack can only discharge at about 1.2 times the capcity (1.2 x 2Ah = 2.4A). The current draw from the motors is therefore higher than the battery can provide.

### Example 2

You selected two 7.2V DC gear motors which consume 1.5A each under normal load, and up to 2A each under stressful situations. This means that the battery needs to be able to provide at least 3A normally and up to 4A safely. If you choose an NiMh pack it would need to be 4A / 1.2C = 3.3Ah. The alternative would be to choose a LiPo pack because they can often discharge at 5C or higher, meaning you would be able to get away with a 4A / 5C = 0.8Ah pack. Granted the capacity is low, and you may opt for a higher capacity pack.

Burst Discharge Rate

### 219 Responses to “Basics: How Do I Choose a Battery?”

1. #### Praveen

Longing for these kind of details for quite a long time, resplendent work dude, LET GOD REWARD YOU

2. #### Sundar Ravi

I want to design a protection circuit (current protection) for the LiPo battery that has to operate between 200 amps
The battery delivers 8000mA/hour at 24 volts.
It has been used to run my 9 motors for my robot can you please suggest me a good current protection circuit?

• #### Coleman Benson

A protection circuit can either prevent a battery from being over-charged, or discharging too much. Unfortunately we cannot provide circuit diagrams or consultation on how to create one, but we can say there is quite a lot of free information online.

3. #### ganz swagger

hlw. I have used 12 servo motor for my hexapod.so could u plz tell me wat should b better ratings of lipo battery to get best performance?i am thinking to use diz rating (800 mah,20A,12.6 V).is it okay?if yes thn how long it can sustain.

• #### Coleman Benson

Be careful when using 7.4V LiPo batteries with RC servos (which normally work best at 4.8V to 6V). LiPo batteries can normally discharge at high current (a meaure of the capacity). The higher the capacity, the longer the robot will run, but also the heavier the battery will be. For hexapods similar to Lynxmotion’s, a 2-4Ah battery is best, and you might get 15-20 minutes of use. 800mA won’t last too long.

4. #### siddharth surya

i need to control 20 servo..which battery shall i use?

• #### Coleman Benson

@siddharth surya You need to add up the current required by all servos (assuming you will use them all at the same time) and then choose a battery which can provide that current. For specific product suggestions, please create a new topic on the RobotShop forum and provide details about your project.

5. #### Abeer

Hallo,
If i have a micro-controller that consumes 150 mw and i wanna use 4AA battery, for how long it will stay till it discharge ?!

• #### Coleman Benson

It depends on the capacity of your AA batteries. If they are 2000mAh (2Ah), and your microcontroller operates at 4.8V (or 6V), then it will theoretically last 2000*4.8/150 = 64 hours.

6. #### carlos p

so i want to power a 12V 0.4A 36oz-in Unipolar Stepper Motor. I was planing on using a 11.1 v 1300mAH lipo battery to power it, power an arduino Uno and a sound board. or should I use my lead acid battery which is powering 2 12VDC motors

• #### Coleman Benson

@carlos p For more technical questions, it’s best to create a new topic on the RobotShop Forum. We’ll be happy to help.

7. #### Jose Ignacio

hello Coleman. Thanks for your post. I have a question: I use a microcontroller (ATMEGA328P, the same as arduino) with a BLE module too, both powered from a CR2430 litium battery (285mAH capacity). The consumption of the complete board (microcontroller + BLE module) is continuosly 0.8 mA but it comes to 4 mA a every 8 seconds (for a very little duration, less than 1 second). The fact is that the battery is going down very quickly: it takes less than 1 hour to put 3.6 volts in the circuit. What can I do? There is something wrong? Thank you!

• #### Coleman Benson

@Jose Ignacio What is the maximum discharge rate for the battery (normally in C). We suspect it might be 2-5C, so it can likely discharge at 1.4A (you need to confirm). Your battery’s capacity is only 0.285A, and it’s likely that your microcontroller is consuming well above 200mA (the BLE unit might consume 0.8mA, but the microcontroller is the one consuming all of the current).

8. #### luis r

I need to make an airboat for a 6 meter race. I bought a quadcopter 3.7V mini DC motor. When i use 2 AA batteries it has good speed, but when i changed them to 1 9V battery the difference was incredible. So, is it safe for the motor and the airboat if i use the 9V battery instead of the 2 AA batteries?

• #### Coleman Benson

@luis r, This depends on the input voltage range of the motor. Normally a 3.7V motor might accept something like 2-5V, beyond which the motor will not operate efficiently, and the life span will be reduced. You need to find the specs for the motor to know if 9V will drastically reduce the motor’s life, or if 9V is within the tolerable range.

9. #### divyanshu

is it possible to get 8amps under normal condition from a 4.5v battery……..is there some other equipment to get this high power

• #### Coleman Benson

@divyanshu it depends on the battery, chemistry and discharge rate. Simply look at the battery’s discharge specs.

10. #### Abheerup

hey man, thank you for this information.

i have a query. I am using 4x 9g micro servos which run at 4.8v to 6v
& atmega 328 working at 5v.
Both are connected via voltage regulator 7805.
To power all these, i have an 11.1v lipo 1000mah 20c.
But i still havent bin able to use that battery as i fear it might burn the whole system.
How do i deal with it?

• #### Coleman Benson

@Abheerup You are correct to assume that powering normal RC servos at 11.1V will destroy them. Most 9g servos consume more current than normal standard sized RC servos, so using the ATMega’s pins to provide power is out of the question. You can split the output from the 11.1V; part of it goes to power the Arduino directly, and the other goes to the regulator (which can handle up to 1.5V) to power the servos. You would need to split the servo cables as well: red and black to the regulator, and signal and black to the Arduino.

11. #### Robo Lis

i have UDI U818A quad-copter and 3.7 li-po batt at 500ma or the largest updrade @ 1.3a is a joke for flight time 10 minutes (maybe)
can i make a pack out of 3aa ni-mh ELB2800! the batteries should hold up that alot longer flight time do you think the electronics of the 3.7v copter can handle nominal voltage of (roughly 4.5v)

• #### Coleman Benson

@Robo Lis Most quadcopters have a flight time of 10-15 minutes, with a few around 20min. It’s always a compromise between storage capacity and battery weight.

12. #### Robo Lis

so would i damage the electronic with 4.5 volt power (i’m leaning toward 3aa @ 4.5 v)
or should i go to li-ion 3.1a single rated at 3.7v

• #### Coleman Benson

@Robo Lis 3xAA would weigh considerably more than a 3.7V LiPo of the same capacity, and might not be able to provide the required discharge current. Also, the electronics may not be able to handle 4.5V.

13. #### Robo Lis

thanks so back to square one or perhaps a single li-ion @3.7 THANK YOU

14. #### Vaughany

G’day, if I put a 12v battery in a 1.5V device by mistake is that likely to kill the motor??

15. #### Rob

Hello, I’m still a little confused with lipo batteries. I’m currently using a 7.4volt 2000mAh 50C Lectron Pro lipo battery with continuous discharge. I picked this up because this beast should be able to output 100 Amps (2000mAh*50C/1000, yes?) I’m using this to run 6 Hi-tec servos and I’m approximating 1.5 A load with approx. 5v requirements each. In other words, there is enough amperage and the voltage is more than suffice. I created step-down voltage regulators. However, when I run them, it seems to run only when there is a limited amount of servos attached…..seems to indicate not enough current?
Is my calculations correct?

• #### Coleman Benson

@Rob if you’re using a voltage regulator to drop the voltage, the output current is then restricted to what max current the regulator can provide.

16. #### ahasan

can you please recommend a battery to power up 17 mg996r motor for my robot?

• #### Coleman Benson

@ahasan Unfortuantely RobotShop does not sell the MG996R. Do you plan to use the servo at full torque and if so, know the maximum current of the servo under full load? If not, you need an estimate of the current for each servo, as well as how many of the 17 servos you’ll be using at any given time.

17. #### ahasan

mg996r : running current – 500ma-900ma (6 volt)
stall current – 2.5 A(6 volt)
breakdown voltage-20 volt
do you think using a 11.1v 5000mah lipo battery with be useful?

• #### Coleman Benson

@ahasan If you have all 17 servos in a stall condition (operating at stall torque), they will consume 17×2.5A = 42.5A. The LiPo battery would need to discharge at 42.5A / 5 = 8.5C. Look at the LiPo battery’s ‘C’ rating to see if it can do above 8.5C continuous discharge. Again, hopefully you will never encounter stall conditions on all servos.

18. #### ahasan

Do you think that Turnigy nano-tech 12800mah 2S 40~80C Lipo Pack battery will work for me?

• #### Coleman Benson

@ahasan 40C means a min cont. discharge of 512A. Not a problem at all for that battery.

19. #### ahasan

i tried the Turnigy nano-tech 12800mah 2S 40~80C Lipo Pack battery. but my 17 dof robot servos vibrates a lot. too much vibration. what could be the problem?

• #### Coleman Benson

@ahasan It could be that the servos cannot handle the torque – they might not be powerful enough for your application. We don’t have any experience with Turnigy to know comment on their quality or reliability.

20. #### ahasan

i suppose the 12800mah battery doesn’t constantly give 12.8 amp? do you think high current can make my MG996r servos vibrate ? can i use any kind of shield for proper servo currents with the arduino and the battery?

• #### Coleman Benson

@ahasan The “C” rating for discharge tells you how much current the battery can provide, where “C” is the battery capacity, but in Amps (not amp hours). 1C discharge for a 12.8Ah battery would mean 1×12.8A = 12.8A. You said it can discahrge at 40C to 80C, to that means 512A to 1024A. Regarding using an Arduino Shield, it needs to be able to handle ~17A of current – it gets “iffy”.

21. #### S

I need to charge bluetooth module: 3.3 v, microcontroller: 5v and gyroscope:3.3. Total current is 2.6Mah. WHat will be the best way?

• #### Coleman Benson

@S You mean power them all or charge a battery? Some microcontrollers have a 3.3V output pin, so 5V to power the microcontroller and 3.3V to power the sensor and BT module perhaps?

22. #### Geoffrey Wight

I live off-grid and I have a voltmeter that indicates the charge of my battery bank. It operates off a 9v alkaline battery. Could the 9v alkaline be substituted with a 9.6v 2.2ah battery? My current understanding is that a device will draw only the current it needs so if the voltage is close enough the higher amperage shouldn’t bother?

• #### Coleman Benson

@Geoffrey Wight Correct. If your device is 9.6V tolerant, then higher capacity simply means it will last longer. The one exception, which is likely not the case here, is when the higher capacity battery cannot discharge at the required current (normally affected by battery chemistry).

23. #### medicus

I have two 6v dc motors connected to L298N Driver…. Should I use 12 volts battery? Sorry for my stupid question.

• #### Coleman Benson

@medicus You should use a 6V battery (powering the L298N), not a 12V battery.

24. #### Mohamed

Dear Mr Benson,

Thank you for this very well-written post/tutorial. I am currently working on a hand prosthetic and am developing a wearable wristband to read emg signals. The wristband contains the following:
1) Arduino Pro mini 5V ( Typical supply voltage: +5.0 V, Typical supply current: 10-25 mA)
2) Transmitter Module ( Typical supply voltage: +5.0 V, Typical supply current: 03-10 mA)
3) Myoware muscle sensor ( Typical supply voltage: +5.0 V, Typical supply current: 09-14 mA)

I am currently looking for a battery to power these components. The battery needs to be as small and as light as possible. It also needs to be rechargeable. There is no minimum operation time due to the project being a prototype, however, the longer the duration the better. I am currently looking at the s 200mAh 2S 7.4v 20C LiPo Battery
( http://www.overlander.co.uk/batteries/lipo-batteries/eflite-umx-beast-type-lipo-battery.html )
and wanting to connect it to 5V Step-Up/Step-Down Voltage Regulator S7V7F5 to connect the battery directly to the VCC pin bypassing the Arduino low efficiency regulator.
( http://www.hobbytronics.co.uk/s7v7f5-5v-regulator?keyword=5v%20step-down&category_id=0 )

Now I understand I need a protection circuit board/module to protect the Lipo battery. Can you please advise me on these protection boards. Also please tell me if you think that another battery type will better suit my needs.

25. #### Mohamed

A large update on my questions which I also posted on the forum:

I am currently looking at a 240mAh 1S 3.7v 25C LiPo Battery with a 5V Step-Up/Step-Down Voltage Regulator
https://www.coolcomponents.co.uk/5v-step-up-step-down-voltage-regulator-s7v8f5.html

Question 1) Will the battery and voltage regulator combined work fine with the components mentioned above?
Question 2) Would I need a PCB for the LiPo?
Question 3) Is there another battery type or battery spec that better fits my needs?

26. #### daan

Hi, so I have a 12V DC motor, 4.9W with a max load I = 410 mA.
I don’t need it’s full power, so I wanted to use an accupack of 7.2V (6 cels) to power it. The motor has to work for only 20 minutes (= 123mAh). Would this be possible and if so, do you have an idea wich accupack I should use? thanks!

• #### Coleman Benson

@daan If the stall current is 0.41A, you can assume the continuous current is around 0.12A, so if you want it to last 20 minutes, you’d need a 12V, ~40mAh battery. You might consider an 11.1V, 50mAh to 100mAh LiPo pack: http://www.robotshop.com/en/power-systems.html

27. #### med

I’m currently working on a Robot with 2 dc motors (6v nominal, and 1.08A) with 4 to 6 servos, I want to use 11.1V lipo packs, which packs should i choose? ( C rating and the mAh) help

• #### Coleman Benson

@med If you are using RC servos which operate at 4.8V to 6V nominal, an 11.1V LiPo will kill them, so you either need a separate battery or a voltage regulator. The C rating is the capacity and the discharge rating is normally provided as a multiple of the ‘C’ rating. The capacity relates to how long the robot will last. For example if your 11.1V battery has a capacity of 2000mAh (2Ah) and can discharge at 5C, that means it can discharge at 10A, which is more than enough for your motors.

28. #### marcus jones

I am making a robot with 9 mg995 servo motors, I tried to google how much volt each requires but I didn’t find an answer, my question is what battery should I get, I read horror stories about batteries blowing up, I don’t want that happening, I heard nimh batteries are the safest but still tend to explode, please let me know what battery I should get to run 9 mg995 servo motors for my robot

• #### Sébastien Parent-Charette

@marcus jones: According to datasheets we found online, the TowerPro MG995 servomotor uses a voltage range of 4.8-6.0 V DC (normal RC servomotor range). Your best bet would be to use NiMH 6.0 V DC battery packs, such as this one. Depending on how many servomotors you will use / how long you want it to last, you may want a larger capacity batter pack. You can search for other 6 V DC NiMH battery packs here. You may also want a servomotor controller board (if using with a computer or a microcontroller), such as the SSC-32U. Concerning battery fires/explosions, this should never happen if you battery can provide enough current for the use you make of it. Batteries usually only overheat (and possibly get damaged) when they are forced to provide too much current quickly or when they are over-charged. Of course, never charged a battery pack without supervision. You should be using a smart charger, such as this one.

29. #### tony

thnx! this really helps, one question though: I’m planning to use a 6 V 3700 mAh NiMH battery pack, to power my robot. it will have two 6v DC motors and two 6V servomotors. But is also need 9V + to power the microcontroller. a step up converter might be an option, but is it as simple as just putting a step up converter between the microcontroller and the batterypack, and combining the grounds from the motors to the battery whit the grounds back to the microcontroller?

• #### Sébastien Parent-Charette

@tony: Which microcontroller are you using? In most of our Lynxmotion kits, we use a 6 V DC battery pack directly with our microcontroller board without issues. You may want to add a capacitor to prevent brownouts. Most on-board voltage regulator can handle about 1 V of difference between input and output at low current drains (such as with a microcontroller chip). If your board really needs 9 V DC or more, than you can use a step-up converter (such as this one) and link up the grounds together.

30. #### Mike

Hi, I currently have 2 12V DC Geared Motors with specs:
1) Free run current : 900mA
2) Stall Current, 12V: 3400mA
I want my system to operate for atleast 6 hours, and I have an 11.1V LiPo 2200mAH 30C. Will this achieve the operating time? If not what what should I do to achieve this?

• #### Sébastien Parent-Charette

@Mike: Unfortunately, probably not. At 900 mAh for the motor (with no load), the battery would last at most a bit less than 2.5 hours. Of course, when you add a load, the motor will use more current. Plus, its nominal voltage is 12 V DC, not 11.1 V DC, so it may use a bit more current than normal. The actual current required for the motor will vary with the load, but it should be roughly at 25-35% of the stall torque (rule of thumb/approximation). We recommend that you test your motor (loaded) with a multimeter in series to measure the average current required. For our example, we will assume a continuous current of 1775 mA. If this was to run for 6 hours, you would need a minimum battery capacity of about 10650 mAh (= 6 h x 1775 mA). One possible option would be to combine two RB-Sta-11 in series to provide enough voltage, current and capacity.

• #### Sébastien Parent-Charette

@tony: This should not be too much of an issue in most cases. You may wish to add a capacitor over Vin/Gnd to prevent possible brownouts. The recommended/optimal minimum voltage input for Arduino boards is 7 V DC but the minimum is 6 V DC so you should be fine.

31. #### Mike

@Sébastien: Hm, I thought the discharge current of the LiPo plays a role here from what I’ve read (but probably misunderstood) above between the conversation of @Coleman & @daan.

From what I understood, if my total stall current say = 7A; and my LiPo has a ‘C’ rating of 30C, so I get 7/30 = 0.23A. Thus if i want to run it for atleast 6 hours, it’s 0.23*6 = 1380mAh.
I would now require a minimum of 1380mAH of that LiPo battery (of 30C).

So, this is a calculation mistake then? Thank you for reply by the way.

• #### Coleman Benson

@Mike A LiPo battery may have the following specs: 11.1V (3S), 5Ah, 25C discharge. The 3S represents 3x 3.7V = 11.1V, the 5Ah = 5000mAh represents the capacity, and the 25C represents the maximum discharge rate, which would be 25 x 5 = 125A. If your motor consumes an average of 7A, this battery would last 5/7=0.714 hours (assuming 100% efficiency).

32. #### Jack

Good afternoon, thank you for the excellent information you’ve posted on this awesome site. I am currently building a prototype cooling unit using 2 CPU 20mm fans. (DC 5V 0.5W). Can I use a standard 9V battery? What would you recommend? Thanks again.

• #### Coleman Benson

@jack It depends on the motor’s voltage range / tolerance. Why not use a wall adapter instead (a battery won’t last very long).

33. #### erwin

can i use AC adptor 8v 0.5A to charge my 3.6V 2000mah ni cad battery? sorry im a newbie…

• #### Coleman Benson

@erwin If you’re new to electronics, it’s really best to use an actual charger to charger batteries (a lot can go wrong and be dangerous – it’s not worth saving a few dollars by trying to create your own charger).

34. #### jp

respected sir,we are trying to run stepper motor having operating voltage between 12-24 V and current capacity 2.8 A ,with motor driver circuit having maximum current bearing capacity of 5 amp and 2-5 volt.we earlier tried to run it with battery having capacity of 12 V & 5Ah and motor driver circuit is getting over heated.which battery we can used in this case which can continuously run the motor for 2 hours ??? Is that any problem with motor driver?

• #### Coleman Benson

@jp If the motor controller is getting hot, that means it cannot provide the necessary current for the time you need, and you might want to find a different controller. The battery’s discharge current only affects how much current is available to the controller; from what you described, the battery can provide the necessary current.

35. #### VENKAT

sir, I am building a hexapod robot with 18 servo .i am using 7.4v 1500mah 20c Lipo battery. but i need a 6v to all 18 motors .how can i get
6v without reduction in current.

36. #### supreeth

i need to use 4, 12v high torque motors which can draw upto 8a current each while starting, and i am planning to use one 12v 10ah battery for all four, is it a good idea??

• #### Coleman Benson

@supreeth It depends on the chemistry and max discharge rate. If all four motors operate, the total current draw would be 32A, so the battery would need to be able to discharge at a minimum of 3.2C (likely 4C, and 5C is better).

37. #### Justin

Hi, thanks for the interesting website. I’m new to this and creating an off road vehicle controlled from a Raspberry Pi. I have 4 x 12V DC motors rated as 100RPM, 0.61Kg-cm and 0.23A. Can you recommend the spec of battery best to use? I assume Lipo 11.1V is better than NIMH 12V

• #### Coleman Benson

@Justin If the current draw is 0.23A, and there are four motors, then a quick estimate would be that all of the motors can consume 1A. The battery capacity will determine how long the robot lasts, but the higher the capacity, the heavier the battery. LiPo is normally lighter than NiMh and can discharge at a higher current. They are more difficult to use, and chargers tend to be more expensive.

38. #### Arsalan

Hey bro,
I am making a robot and I am using an arduino mega as the controller.
I am using 4 DC Motors, 02 servos and a stepper along with a couple of sensors. There are limitations on the weight of the device.
Can you suggest me the best battery to power my device with ?
Cheers

• #### Coleman Benson

@Arsalan If it’s a mobile robot, you should choose a battery pack whose voltage corresponds to the nominal voltage of the motors; ideally this will be above 7V so you don’t need a second battery pack. The capacity affects the time of operation as well as the maximum discharge current.

39. #### Matthew

Ok here is a question I have an Ironman suit lights, speaker, and helmet motor that movies faceplate up and down. At first I was running 3.7 volt batteries in a pack of 4 to run it. Would it be better if I ran it off of a 9.6 battery pack because of how long it takes to charge the 3.7 volt batteries and I have multiple 9.6 battery packs? Weird question but would love some advice please.

• #### Coleman Benson

@Matthew It depends on the voltage of the main actuator. Can you create a new post on the RobotShop Forum with details of the components (a photo or two would be nice) and re-state your question?

40. #### Sondos

I am working on a car using 2 DC motors ,, one servo ,, 4 batteries each 1.5 volt ,, first when I wired the first motor it works but when I wired the second motor to the shield nothing worked ,, I think that happened because of the batteries but I am not sure what should I do ? ,, Thanks in advance for helping me ..

• #### Eric Nantel

@Sondos, We suggest you to open a topic on our RobotShop Forum for proper help as going back and forth here is not easy.

41. #### amir

Is it OK to Replacing the 7.2v 800mah li-ion battery pack w/ 7.4v 2000Mah for jvc dv camera ?

• #### Sébastien Parent-Charette

@amir: It is most likely not a good idea to replace the battery pack with a different one. The discharging of the new pack might be fine, but if there is charging circuitry inside the device, it most likely will not be able to handle a different battery pack than the one it was intended for. We strongly recommend against this as it could cause damage to the battery pack, the camera and its users and other issues such as possibly catching fire.

42. #### Shourya

I am trying to make a vacuum cleaner. I am using a battery of 12 dc Volts with RPM greater than 6000. Please help me choose a battery for that!

Sir, you have done a great job! Keep it up! Best part is that you make sure to reply to others and help them!! Keep up the good work Sir.

• #### Coleman Benson

@Shourya The choice of battery will depend on many factors. For a Vacuum, we suggest as 1V NiMh or 11.1V LiPo. The capacity will affect the weight and discharge rate (i.e. maximum current).

43. #### dwain

hay, great stuff. can ask is it ok to us a 9.6v 800mAh in a rc car that came with a 3.7v 5mAh battery? thanks

• #### Coleman Benson

@dwain 3.7V 5mAh sounds way too small to be useful. Do you mean 500mAh? If the electronics / motors operate at 3.7V nominal, 9.6V may fry everything.

44. #### shahmed

greetings

Greetings, firstly let me send towards you blessings for this very well assembled and informative rare piece of gold. Secondly i was wondering how to calculate capacity for alkaline batteries they do not have any info about mAh. Thankyou 🙂

• #### Coleman Benson

@shahmed From what we understand, you have a battery but do not know its capacity? Ideally the manufacturer should provide this data, but we have seen that many suppliers specifically leave this out; we suspect this is done because there is a lot of contention among battery suppliers to put a “real” capacity – in the past, certain manufacturers have put values which would increase sales, but which could not be reproduced. As such, many of them simply add terms like “high capacity” or “long life”. You should be able to write to the manufacturer to get them to at least give you an idea of the capacity and if not, you may want to consider a different brand.

45. #### Renante Quintano

Greetings,

I have an ATS controller with a power 8-36VDC, Max 1.2A. What battery should i used and rating? We test 2 pcs Sealed maintenance-free-lead-acid battery in series connection 12V/1.3AH/20HR but it doesn’t work. Thanks.

• #### Coleman Benson

@Renante Quintano You want to power the ATS using a battery? Not sure why the lead acid battery would not work (are you sure the battery is 1.3 Amp hours? that seems low).

46. #### Arto Varonen

I have a 7.2V motor what has been used with Ni-Mh AA P 400mAh 7.2V battery and i want to change it to working with usb so i can plug any powerbank to it what has 5V. Is this ok or do i need something in between and can the motor get enough electricity to work?

• #### Coleman Benson

@Arto Varonen The motor will likely operate at 5V, but at lower efficiency. You need to know the maximum current which the power bank can provide in order to know if it can work with the motor.

47. #### Sam

Hi,

I am building a robot fro my school project, it has a two 12 volt dc motors with encoders to drive the robot around using tank treads. the robot will weight about 1Kg. What would be your suggestion on the voltage and the Ah of the battery? I was thinking of using a 14.8 volt LiPo battery with 3300mAh.

• #### Coleman Benson

@Sam If the motors are 12V nominal, then it would be best to use an 11.1V LiPo. Note that the capacity determines how long the robot will operate, but the higher the capacity, the heavier the battery. 3300mAh sounds ok.

i have a modem with a input 9v – 0.6a if i want to run in battery when power is down for 1 hr. how much v battery should i use.. ??

• #### Coleman Benson

@arshad There are not many 9V batteries which are useful for things other than small electronics. You might need a higher voltage battery and a voltage regulator. If your device consumes 0.5A, you’d need a 0.5Ah battery.

49. #### PUSHPDEEP P MISHRA

hi coleman,
im using portescape 30gtr82 dc motor . i am unable to figure out which battery to use.
i want to make my device portable enough.

• #### Coleman Benson

@PUSHPDEEP P MISHRA We cannot seem to find that prodcut online. Choose a battery based on the motor’s nominal voltage. Within the specs, it should give you the current draw at maximum efficiency. Therefore the battery capacity can be calculated as current draw multiplied by the number of hours of use, multiplied by the efficiency. For example if a motor consumes 2.4A, you would need a 2.4AH battery to have the motor last 1 hour. You also need to check that the battery’s discharge current is enough for the motor.

50. #### Suraj

Am building a wireless robot and i want a good decent battery for that. I am taking in use 12v 1.2amps battery, it’s too big in size and heavy too. So, please suggest me an alternate battery for this, which should have somewhat same configuration and lightweight and also bit small in size.

• #### Coleman Benson

@Suraj We would need to know a lot more about your setup in terms of components. Please create a new topic on the RobotShop Forum and provide as many details as possible.

Hi i have ultra spike dinasour fisher price the issue is when it move it stop when i restart using power switch everthing work again except if i command to walk it stop this has been the common issue for this toy one guy says he replaced the the battery with the higher volts and it work again my question is how far i can go up with the required battery which is 9.6v,1300mAh to avoid the short circuit thanks!

• #### Coleman Benson

@Chad It’s best try the same battery as was suggested by the person who hacked the product – it’s a question of what voltage the electronics can tolerate.

52. #### Maria

I’m confused by the nominal voltage. I have two 4.5 6S 22.2v high discharge LiPo battery and i need to power a 24 V hub motor. I read that the cells can be charged up to 4.2V, what does that mean?

• #### Coleman Benson

A 6S (six cell) pack contains six 3.7V (nominal voltage) cells. When charging, a charger will charge each cell to around 4.2V, so the total pack will end up providing 25.2V for a while, rather than 22.2V.

53. #### Dwayne

Hi. I’m using 4-6 k2 waterproof high torque servo motors. What would be the best batteries for me to use?

• #### Coleman Benson

@Dwayne Unfortunately we are not aware of these servos to know the nominal voltage, though it’s likely 4.8V to 6V (please confirm though). You then need to check the max current per servo, then multiply that by 4 to 6 to get the max continuous current required by the battery. The last selection is the battery’s capacity in order to know how long the servos will last between charges.

54. #### Sucheta

I need to charge my i)1000KV brushless DC motor and propeller ii)4 servo motors for wheels.please suggest the needed Li Po batteries

• #### Coleman Benson

@Sucheta Normally BLDC motors need 2S, 3S or 4S LiPo, while standard RC servos operate at 4.8V to 6V. You should therefore choose high voltage RC servos and a 2S LiPo pack (assuming the BLDC motors operate well at 7.4V.

I’m using 4 Johnson [ 800mA 12 ] for robot ~ i want to make portable which battery should I used

• #### Coleman Benson

@Nishadvijay You need a battery which is at the nominal voltage of your motors. If 800mA is the continuous current under load, the battery needs to be able to provide at least 2.4A continuously. The capacity is a measure of how long the battery will last between charges.

56. #### yogeshkumar pustake

hi sir , we use 24v 250 w dc gear motor for our project , so sir for minimum 1 hour riding our vehicle which battery we select ?

• #### Coleman Benson

@yogeshkumar pustake It sounds like at maximum power, the motor would consume 250/24 = 10.4A. If you use two motors, it would double up to 20.8A. For 1 hour ride time, you would need a 24V 10.4Ah battery for one motor, or 24V, 20.8Ah for two. There is a lot more involved like efficiency etc., but this should give you a ballpark estimate.

can i know how long does the 9V battery can be used for 12V motor

• #### Coleman Benson

@Muhammad Syahir If you mean a normal 9V battery, which tend to have up to 150mA capacity (maybe a little more), it won’t last long at all when used to power devices other than electronics.

58. #### marvin youngstrand

can you charge a 12v, 1.3 Ah Li-ion battery with a 12v dc 500mA charger

• #### Coleman Benson

@marvin youngstrand Normally a LiPo would be 11.1V rather than 12V. You really should choose a LiPo compatible charger (LiPo batteries are dangerous) and ensure the charger is compatible with 3S LiPo batteries. If your battery is special and is 12V nominal, you would need to consult with the manufacturer as to how to charge it.

59. #### akshay

Hello Sir, I am working on a Project. I need 6, 12 volt Dc Motors. But I m confused about The battery. Can u please help? ?

• #### Coleman Benson

@akshay You would ideally an 11.1V or 12V battery which can output at the current needed by all six motors at their peak. The capacity will determine the time between charges.

60. #### akshay

Hello Sir, I am an engineering student. I am working on an agriculture robot. I need 6 noS. Of 12v dc motors. But I am confused about which motor should I use.? Can u please help? ?

• #### Coleman Benson

@akshay Feel free to create a new topic on the RobotShop Forum detailing your project and what you need help with.

61. #### Arnaud

Hello. Thanks for your very useful post.
I am currently working on a very low power device logging data from a GPS chip three times a day. I would like to have it running for 1 year at least. What kind of battery/technology would you recommend me? size and weight matter (as small and light as possible) but price does not!
Thanks!

• #### Coleman Benson

@Arnaud If it needs to run for a year without the chance to recharge (solar panels or wind turbine for example), most normal batteries would discharge over the course of a few weeks / months (certain exotic Lithium based battery tech may last longer). You might consider changing the technology used entirely and consider a hydrogen based mini fuel cell, which charges a regular LiPo battery. If you need more advice / ideas, please create a new topic on the RobotShop forum and provide details of your project.

62. #### Alex

Hi,
I am currently building a project where I require to power two 12 V dc gear motors(pololu) with stall current at 5A. I planning to use a 12 V 9Ah lead acid battery for my project. The motors will be connected to a motor driver (L298N) that is rated for 4-40 V, 2 A. Now I am not sure if I should connect the motors to the battery without damaging them. I am very new to electronics and really stuck. I have been testing my project so far using a 12 v adapter running on AC. Please help or suggest something.

Thanks
Alex

• #### Coleman Benson

@Alex You would connect the battery to the motor controller, not the motors directly. The battery may be on the heavy side if it’s a mobile robot.

63. #### Bassel

hello there, I have a robotic arm and I`m using 2 MG996R servos and 5 MG90S micro-servos I want to use the best battery that can last over 5 hours or even longer .I was going to use a powerbank with 5v and 20000mAh but then I knew that its maximum output current is 5.5 A . can you help me to choose the best battery or power source for my robotic arm .

• #### Coleman Benson

@Bassel Your servos should not consume over 5.5A.

64. #### brijesh

sir which battery should i used for operating 4 servo motor simultaneously??????

• #### Coleman Benson

@brijesh If they are normal RC servo motors, you can use a 6V battery. The capacity will determine how long the servos can operate between charges.

65. #### Simon

Hello Sir,
Are there any disadvantages of using a regular powerbank and steping up the voltage with a boost converter?

• #### Coleman Benson

@Simon Not sure what you mean by a “power bank”. Normally you tend to reduce voltage rather than step up.

66. #### Arifa Fatima

hello
I am using Two motors of 250W, 48V hub motor .
can you tell me how much battery i need and calculation also?

• #### Coleman Benson

@Arifa Fatima The current is likely ~5A, so you need a 48V battery which can provide at least 10A continuously. The capacity will determine how long the motors will last between charges. However, without additional specs for the motors, we cannot be certain they will not draw more than 5A. You really need more info.

67. #### iyako

well done sir, i can see you are really doing a great job. please i want to know if using 3 of my 3.7v battries would be okey for a 9.6v motor

• #### Coleman Benson

@iyako 3.7V is quite far from 9.6V and it likely would not operate very efficiently.

68. #### Manohar

Hiii…. i need to know which battery suits for two stepper motors of 3.3v. And how many hours does it works if once full charged..

• #### Coleman Benson

@Manohar You might try a 3.7V LiPo. The capacity will relate to how long the stepper motors are powered between charges.

• #### Coleman Benson

@Gulzat What is the operating current under load, how many motors do you have any how long would you like the battery to last?

69. #### Gulzat

@Colrman Benson The rated current is 3.17 A. I would like to use it for an hour. Also, I want to find rechargeable battery

• #### Coleman Benson

@Gulzat You would need at minimum a 12V, 3.17Ah battery. However, with inefficiencies etc., it’s best to opt for a 5Ah battery with at least 1C discharge rate.

70. #### Chuks nelson

I appreciate your effort sir……I want to buy 4 dc motors each have a max voltage of 170v each and a continuous current of 500amp….so I want to ask how many voltage is required to get maximum RPM from the 4 dc motor????? Is it 170×4 dc motor=680volts???

• #### Coleman Benson

@Chuks nelson You’d need to either contact the manufacturer or test it by applying increasing voltage. No, each motor needs 170Vm so you would need 500 x 4 = 2,000A. Note that the motor on a Tesla (the car) operates at 375V and is around 285,000W (therefore under maximum power would consume 760A. If you are making a mobile platform (or car?) with four 85kW motors, you’re making something even more powerful than an S60 Tesla. Your R&D costs are likely going to be in the \$100k range.

71. #### akshay sharma

thanks for the article sir….. My basic question is how do a battery of 12v, 35 amp runs a motor of 12v, 90amp ?

• #### Coleman Benson

@akshay sharma The battery needs to be able to discharge at 90A. This often relates to the ‘C’ rating. If the capacity if 35Ah, and (for example) it’s rated for 3C discharge, it would be able to discharge at 3x35A = 105A. Again, you need to check the rating of your battery.

72. #### Thirumalaivasan

sir,I am using 4 12v dc motors,each needs 2amps and 4 16kg-cm servomotors,each needs 2amps and operating voltage [email protected] and 3 35kg-cm servomotors,each needs 3.5amps and operating voltage8.4v.
Now,i have selected to use one 12v 7.2ah battery for 4 dc motors and one 9v,3.7ah li-po battery for the 7 servomotors(because it has 5c current rating as you said).
Now,i want to know,is that power source is ok for my requirements?

• #### Coleman Benson

@Thirumalaivasan We would actually need a few more details. Can you create a new topic on the RobotShop Forum and give us more of an idea of the project, and provide links to the products?

73. #### Dhananjaya Pande

Hi. I am using a micro controller that consumes 50mA, a dc brushed motor that consumes 0.4A when working and a fan consuming 0.4A. The motor only works for 40seconds in an hour. I am planning to use 8AA batteries because I need 12V to run all the things. Can you tell me in how much time will the batteries run out?

• #### Coleman Benson

@Dhananjaya Pande You need to know the capacity of the batteries (if they are 1.5V AA, they can be from 0.5A to ~1.5Ah). Get a sense of how much current will be consumed each hour (A) and divide the capacity by the hourly current draw.

74. #### Chandan Kowli

Hi..I am assembling a RF micro controller circuit/Unit to control 2 servo motors which are 7.2V each.
I am in the stage of purchasing Batteries and also the adapter to charge them.(my first ever attempt in a DIY gadget)
So I have chosen to use a 7.4v 2200mah Li-Ion Battery (2×3.7v)

I am currently not sure of the adapter/charger to use….’mah’wise.
There is one available which is 3000 mah (intelligent charger- 8.4V 3A AC DC Power Supply Adapter Charger For 7.2V 7.4V 8.4V 18650 Li-ion Li-po Battery).
The input voltage of the circuit board: 7.4V
The input current of the circuit board: 2-4A
I am not sure if I can use a 3A charger for charging a 2.2A, 7.4v Li-ion battery. I read about the battery either the battery dying early or exploding is the amps are more…Is that true?
Would you please explain and guide me regarding the appropriate choice of charger here…
Thanx a lot…

• #### Coleman Benson

@Chandan Kowli Can you create a new topic on the RobotShop Forum and provide a link to the battery pack as well as the potential chargers? You can use the same text that you used here.

75. #### abu

Sir Can I run 7.5V RC car with 11.1V 25C Lipo battery. I tried it and found the wheels rotating at great velocities. But I’m afraid it would burn the Motors

• #### Coleman Benson

@abu It really depends on the motors themselves and if they tolerate 11.1V. To know for certain, you’d need the specifications of the motors, which is not always available. Hard to give an answer.

76. #### Tejas

I am making​ a BB8 DROID which is from The Star Wars – Force Awakens , movie .
It includes- Arduino Uno, Bluetooth module, motor driver which will control powerful dc motor of 4 to 5 kg-cm . Then which battery should be used in this project

• #### Coleman Benson

@Tejas Many batteries would work – you need to know the continuous current draw of your motor, and its nominal voltage, and then determine the max weight you can add, and see what batteries are in this range.

77. #### Patrick

Hi,

Thank you for putting this together!

I am designing a robot for use in my class. It has four of these: http://www.robotshop.com/en/6v-285-rpm-gearmotor-w-encoder.html driving these: http://www.robotshop.com/en/mecanum-wheel-set.html. I’m using two of these drivers: http://www.robotshop.com/en/10a-5-30v-dual-channel-dc-motor-driver.html, and controlling the whole thing with an Arduino Mega. I’ve been testing it with a 6V 4.5Ah lead acid battery (https://www.amazon.com/Rhino-SLA4-6-4-5Ah-Sealed-Battery/dp/B00G5GXY4C), but gosh, is it heavy! Can you recommend a battery (or two) that I could use to adequately power this robot while saving weight?

BTW, I also plan to mount a claw using 5 of these: http://www.robotshop.com/en/hitec-hs422-servo-motor.html. I’m planning on using a separate power source for the claw. Would a 6V pack of four AA batteries suffice for just the arm? Can I power the motors and the arm with one source? If so, what do recommend?

Thanks!

• #### Coleman Benson

@Patrick Lead acid is some of the heaviest battery tech you can choose. A lighter option would be 6V NiMh pack. A 7.4V LiPo might be out of the voltage range of the motor. Be sure to choose one which can discharge at 5A continuous (or more). You can use the same 6V battery pack to power the 422.

78. #### ahmed maher

HI MR coleman
i have already worked on maintenance project with robot ,and it’s battery has been damaged it was with 24v 17ah rechargable and can’t find it because it was designed special for that robot ,now i do another one by using ni-mh 1.2v 9ah but it go to be damage also.
i asked what about li-ion battery type i think it’ll be more compatible for use than ni-mh type ?

• #### Eric Nantel

@ahmed maher, It’s important to understand the limits of the Li-Ion batteries. One of which will be the constant monitoring of voltage and to cut the supply if you go bellow a certain point. It also require individual cells balance and charge.

79. #### Hey

Hi….I have about 3-4 feet of rbg led strip lighting…I’ve been running them of a 9v battery…but I saw a 1300 mah 12 rechargeable battery…I was wondering if the 12 v would be too much for them…and how long it would last compaired to the 9v….the 9v usually lasts a few hours super bright then starts to lose brightness….and thank you…an e mailed response would be better in case I can’t find this site again

• #### Brahim Daouas

@Hey Your RGB Led Strip should have a voltage rating. You can check the datasheet of your Led strip. Applying above the rated supply voltage might damage your LEDs.

80. #### Gordon Saxby

I am building a vehicle which will be driven by 6 Pololu 20.4:1 Metal Gearmotors High Power 12v (https://www.pololu.com/product/3203). They quote 300mA (max) free-run and 5.6A stall (!). The vehicle will have a Raspberry Pi (v3), probably other controller board(s). How do I work out the battery requirements and which type would be most suitable? Pololu recommend keeping well within the stall current – how would I achieve that?

81. #### Allan

Hi i need your advice on battery power for my son first build of unmanned surveillance track vehicle. The chassis is a Dagu Multi Chassis Tank Vsrsion (sparkfun.com/products/12091), using a Dimension Engineering Sabertooth 2×5 RC controller, a Frsky 8 Channel receiver, 4 servo running on 2 channel (2 servo each channel) in receiver via a ‘Y’ servo cable to create a synchronized movement…. they are, 2 servo for Pan & Tilt Camera (Camera and VTX transmitter for FPV power by standalone 2s lipo), 2 servo for Pan & Tilt Searchlight (searchlight LED power to be drawn form main battery via balance plug powering the controller and motors).

The motor that came with the chassis is the DG01 48:1 (sparkfun.com/products/13302), my son decision is to go the Lipo battery route since he have a couple of 2s and 3s lipo from RC cars and Drones.

Our doubt and question here is, can we use a 3s 11.1v 2200mAh 35c lipo and not risked toasting the motors (DG01D) ? If not possible what are the recommended lipo size? These type of motors are faily new to use. Please advice.

Your kind help is very much appreciated.

Thank you,
Allan

• #### Coleman Benson

@Allan The motor you link to is 4.5V nominal, so a 3.7V LiPo might work for the motor, but likely not for the receiver, and not for the servos (pan/tilt). An 11.1V might burn the motors and will certainly burn the servos in the pan/tilt. A 7.4V LiPO has a good chance of burning the servos. You really should use a 4.8V rechargeable NiMh battery pack.

82. #### ASHOK

I want to control two 12v DC motor for 30 minutes which battery do you suggest

• #### Coleman Benson

@ASHOK That is the point of this article. In terms of voltage, you can choose a 12V NiMh, 12V lead acid or 11.1V. However, your motor may have a nominal voltage range, meaning you might not need exactly 12V. Next, you need to determine the average current consumption of the motors in order to get an idea of the battery’s capacity. Last, you need to know the maximum current consumption to know the max. discharge rate of the motor.

83. #### Chris

I’ve got myself a Zumo chassis with a couple of 6v geared motors, and was hoping to use a LiPo or something rather than AA. Ideally a solution where I can also power a Pi Zero W too.
Really want to avoid having two sets of batteries. Any suggestions? Don’t mind what extra I may need, as long as I can get a good capacity/runtime.

• #### Coleman Benson

@Chris You’ll need to check if the motors you purchase are tolerate to 7.4V (2S LiPo). If not, you’ll need a voltage regulator. Since the Pi is meant to be powered at 5V, you’ll need a 5V, preferably 2A+ voltage regulator: http://www.robotshop.com/en/50vdc-regulators.html

84. #### CH rajesh

I just want to make a drone with coreless motors which is of 3.7v each can U please suggest me the type of battery for both motors and RF receiver of 433 MHz

85. #### Maha

my robot consist a servomotor,ultersonic ,ardunio uno and l293D which one of two method i should use

• #### Coleman Benson

@Maha The servo is likely 4.8V, the Arduino operates at 5V or 7-12V via barrel connector, and the L293D is 4.5 to 36. It seems you can get away with a 5V battery pack (most commonly found as a cell phone charger, but check the max discharge current). Alternatively, opt for a 2S LiPo and use a 5V regulator to power the servo, while the L293 and Arduino are powered at 7.4V. You don’t need two batteries.

86. #### Mir Muneeb

Very useful peice of information you shared.i have got a very good basic idea about selecting batteries and there types.still i want to take your opinion that if im using 5 mg966r hitech servos with 4.2-6V required and stall current of 2.5A at 6v then what rechargebale battery would should i use.amd do i need a servo controller for servo connecting to aruindo or can i use the servos directly with arduino?

• #### Coleman Benson

@Mir Muneeb An Arduino can effectively be used as a servo controller (ref. Arduino servo library). If each servo consumes 2.5A under stall, the continuous current should be closer to 500mA. If you operate all servos at the same time, the battery will need to be able to discharge at 3A (or a bit higher). Many 6V NiMh battery packs (4x 1.2V cells) can handle 3A continuous discharge.

87. #### Mir Muneeb

Thank you Sir.i would also like to knw your opinion about how should i switch between 2 programs in arduino.eg im building a rehabilitation glove controlled by myoware sensor which is mode 1 and can also be controlled through flex sensors in another mode.how do i manually select which mode i want to use?

• #### Coleman Benson

@Mir Muneeb That’s beyond the scope of this article. We suggest you create a new topic on the RobotShop Forum and we’ll be happy to answer there.

88. #### Mae

Good afternoon
I’m trying to chose the right rechargeable lithium battery to connect to a mini motor that is 4800-9800 RPM/80 mAh to use as a power source but has a strong suction.  I will built this on a module and all the parts that I am going to use for this module must be small enough to put inside of 2″ round tube. In addition i will use a power on/off switch, green light indictor stated fully charged and this of course cordless using a usb. I need your expertise advice because I am not knowledgeable in this area.

Thank you,

Mae

• #### Coleman Benson

@Mae We’re happy to help, but need a lot more information. Can you create a new topic on the RobotShop Forum and provide the specs for the motor you are using and how long you want it to operate? You should also include the dimensional constraints again as well.

89. #### Jasper

Dear Coleman,
I have a question considering powering a remote controlled vehicle. I want to control two servo’s(a S3003 servo and DS04-NFC Continuous Rotation Servo) which both need a voltage in the range of 4.8-6V and two DC 3-6v Gear Motors(100-120mAh), with an Arduino Yun. I lack knowledge in the area of power supply, so can you explain me which battery would fit these electronics. The vehicle should work for al least 45 minutes. The dimensions are not a problem, but I prefer a light baterry over a heavy one.
Jasper

• #### Coleman Benson

@Jasper The voltage needs overlap between 4.8V to 6V, so you can choose a 4 or 5-cell NiMh pack. You need to sum the max current from each actuator in order to estimate the battery’s max continuous discharge current. The capacity will determine how long it lasts. Take a look through this article for details.

90. #### Jc

Hello Mr Coleman, I have a remote controller running with 8 AA nimh batteries 2700mAh. I’m planing to use a Lipo of 7.4 v 1600 mAh will be enough current?
Thanks.

• #### Coleman Benson

@Jc Normally LiPo can discharge at much higher current than NiMh, and RC remotes tend not to consume much current. 1600mAh vs. 2700mAh means it will not last as long though. For an RC remote control however, 1600mAh should be fine. Just be sure to recharge it regularly.

91. #### FaresWheel

Hello Coleman
The motors I have are rated are 24V 200W 2.5 Amp max. But the batteries are on the market are rated in amp hours. How do I know which to pick?

• #### Coleman Benson

@FaresWheel The two are not directly related. Note that if the motors are 200W at 24V, the max current would be ~8.3A (stall). The battery’s capacity (i.e. stored energy) is measured in amp hours and you should also look up its maximum discharge rate (units are “Amps”). The battery needs to be able to discharge at your robot’s total current requirement, and the capacity determines how long the battery will last.

92. #### Rinkle

How do i see the amps rating in my battery if its only listed in amp hours?

• #### Coleman Benson

@Rinkle A battery’s capacity is measured in “amp hours” while the discharge rate is measured in “C” (or amps). If you do not have a number which says something like 5C or 10A, then you need to contact the manufacturer / seller in order to know that battery’s maximum continuous discharge rate.

93. #### FaresWheel

@Coleman Benson
Ok I see. The battery I’m looking at is described as having “85 Amps 10 seconds”. Do I divide 85 by 10 to get 8.5?

• #### Coleman Benson

@FaresWheel No – that means the absolute max continuous discharge current is 85 amps for 10 seconds. It sounds like a Lithium based battery.

94. #### Subha das

Sir, what volts of battery is required to run one servo and one 6v motor via L293D motor driver. I’m using an arduino uno for my RC car. Please help!

• #### Coleman Benson

@Subha das If you want 6V nominal, and the current drain is not too high, 5x 1.2V rechargeable cells gives 6V, or 4x 1.5V alkaline cells.

95. #### pablo

I am trying to figure out the battery I need for my robot arm and I dont see nominal load current but only find current drain, no load or idle. I also found another one called stalled which is way higher. Can you tell me if I should consider my worst case as the stall current? If I do I would need a very powerfull battery, for example for the hs 5085MG the stall current is 3 amps! Also that information (stall current) isnt available for all servos…? thanks for helping!

• #### Coleman Benson

@pablo If there is no data about current draw, but there is data about stall, you can estimate the max continuous current draw to be around 1/3 the stall value. For the 5085 (a small but power hungry servo), estimate the drain at 1A under load, with some fractional second spikes going higher (especially when it starts moving)

96. #### Mahir Syed

i’ve build a quadcopter with 4 coreless 3.7v (rated current 100mA). I’m connected the motors with 3 AA battery( each 1.5v ).but my quadcopter isn’t flying…do i have to use more AA battery…??

• #### Coleman Benson

@Mahir Syed It sounds like you are using both the wrong motors and the wrong batteries for a multi-rotor UAV. We invite you to create a new topic on the RobotShop forum and provide details of your setup, as well as photos.

97. #### Tushar

I want a battery to support 5 motors all using 3 A continuous current. Another battery for 4 motors (3 A continuous current) and 5th motor with 13 A peak current required for 10-20 seconds only. Kindly suggest the two batteries.

• #### Coleman Benson

@Tushar Rather than a specific battery, you need to figure out if it can be a single battery (i.e. single voltage) and the total maximum continuous current it needs to be able to discharge. At the current you describe, you’re likely best with Lithium (mobile robots) or lead acid (stationary, or large mobile robots). If your motors have different input voltages and you need to have only one main battery, you’ll need high current voltage regulators.

98. #### Rover C J

I want to power three 4.8V mg995 servo motors and two 12V dc geared motors each having max load current upto 600mA for mobile robot vehicle, please suggest me an appropriate rechargeable battery, I’m new to robotics. Arduino mega is used as microcontroller board.

• #### Coleman Benson

@Rover C J Those servos operate best at ~6V, therefore if you want a rechargeable pack, you should consider a 6V NiMh (5 cell) pack which can discharge at 2A max. The capacity is up to you (though it is related to the max discharge rate). The question becomes how to power the MEGA since the barrel connector is meant for 7-12V. You can a step-up voltage regulator (Vin pin on the MEGA) so you only use one battery. https://www.robotshop.com/en/power-systems.html

99. #### Robin

Sir,
I am making a line follower
It has 6 ir sensors arduino board and 2 150 rpm motors (3v to 12v)
I want it to last for around at least an hour.Neglecting the sensors .what battery should I use.i was thinking to get a 1500mAh lipo 3s 40c.Will that be enough

• #### Coleman Benson

@Robin The actuators will actually consume the most current, so without the current under load, we cannot say how much current is needed (per hour for example). If each motor consumes 200mA under load, and you have two motors, add that to the current consumed by your microcontroller and sensors (ballpark estimate at 500mA), meaning your battery should be at least 1.3Ah. Next, factor in inefficiency (around 65% estimated efficiency), so the pack should be 2Ah. This is just a “napkin” calculation and assumes your motors operate at the same voltage. You would need to do the math yourself.

100. #### Agatha

Hey, Thanks for you information.
Currently i am working on RPI3 & I want to run 4 DC gear motor.
I am using L293D motor driver which is giving me almost 3V drop. So, guide me please..

101. #### Yeganeh

@coleman benson
Hi, thank you because of useful text, i design a pipe inspection robot for master project, but i couldn’t find the best solution for my robot, could you help me, and if it is possible please let me have your email address that i can send you photo and information about my robot. Thank you

• #### Coleman Benson

@Yeganeh Happy to help, though we do not offer design / consultation services. Suggest creating a new topic on the RobotShop Forum where you can attach photos and information and ask specific questions.

102. #### Ponraj

I want to run a six 12v dc geared motor 30rpm for staie climbing with various loads and obstacles.Which battery can i use to deliver enough power to pull the loads by the motor

• #### Coleman Benson

@Ponraj You need to know the maximum current draw of each motor. This will also help you determine the battery’s capacity. Note that for stair climbing, the robot needs to be as lightweight as possible, so consider an 11.1V LiPo pack.

103. #### Ethan

I have a 12V dc motor having no load current at 0.65amp and stall current 43.9. Operating voltage is 9-15V. Which battery should i be using to make the motor run efficiently for long periods of time?. Ive chosen a 12V 1.3Amp lead acid battery, wil it the job?

• #### Coleman Benson

@Ethan For highest efficiency, you’d choose a 12V NiMh or lead acid battery, or an 11.1V LiPo. The battery needs to be able to provide at least 15A continuously if you operate at normal load. Therefore a 15Ah battery would last one hour.. for each additional hour of operation, add another 15Ah to the capacity. A 1.3Ah lead acid would only last 1.3/15 = ~6 minutes under normal load.

104. #### Jhon

Hello
I am working on a project where i need to power 7 servo motors
operating voltage: 11.1V
Max current: 900 mA
stall current: 1.5 A
standby current: 50 mA
can a single 3 cell lipo battery
11.1 v 2200 mAh 25 c support this system
how can i protect my servos from being damaged
do i need a voltage/current regulator?

• #### Coleman Benson

@Jhon To confirm, the servo’s operating voltage is 11.1V? Most RC servos operate at 4.8V to 6V. If the servos operate at 11.1V and require 0.9A max, then the absolute max for 7 servos will be 6.3A if they are all operating at max power. A 2.2Ah, 25C battery can supply up to 2.2×25 = 55A continuously, which is more than enough. To prevent damage, if they are normal RC servos, you can add an 800mA fuse between each servo’s power pins and the servo controller (which might be an RC receiver).

105. #### Yash Gupta

Hi sir , I am making wall climbing robot by using suction cups . We are using 12 MG 995 metal gear servo motor ( operating volatege – 6V , current drawn at no load condition – 170 mA , current at stall condition – 1.2 Amp. ) Can you please suggest suitable battery for this purpose ?

• #### Coleman Benson

@Yash Gupta You might want to start with the battery physically outside from the robot (so the robot does not need to lift the weight of the battery), meaning you can use any normal 6V pack (NiMh for example). If you need the robot to support the battery, it would need to be lightweight, and you should really consider 7.4V servos and a 7.4V LiPo pack which saves considerable weight. The pack needs to be able to discharge continuously at roughly 50% of 1.2 amps multiplied by the number of servos in operation. Hard to provide details without knowing more about the project details – consider creating a new post on the RobotShop Forum.

106. #### Akshay Theertha

Hi sir,
Can we find how long a battery can run a load(LED/motor etc) by knowing just Voltage in a battery(V),Current drawn by load(I) and WATT of l load(w), For example: A 9V battery(Non Rechargable and mAh is unknown) is connected connected to a LED which in series with 100 ohm Resister, where current drawn by LED is 25mA, WATTS of LED is 50.4mW, Resistance of LED is 140 ohm, so can we find how long battery can lights up that LED. I have tried lot of methods, pls give some idea that how can i achieve this!

Regards,
Akshay Theertha
IoT Developer and Solution Architect

• #### Coleman Benson

@Akshay Theertha If the capacity and discharge curve are unknown for that battery, you’ll need to do experimentation; measure the current draw and the voltage and time how long it takes. The current draw should be steady with a fixed load.

107. #### Akshay Theertha

@Coleman Benson , Sir if i know just mAh (say 500mAh), then will it be easy to calculate the time right?
like current drawn by led is 25mA, soo (500mAh/25mA)= 20 hours?

• #### Coleman Benson

@Akshay Theertha That would be the correct “napkin math” assuming the discharge rate and voltage were linear. In reality, you’ll get a percentage of that. Therefore you might make that calculation, assume you might get around 75% of that (so 15 hours), and then test how long it actually works (might be somewhere between 15 and 18 hours). Note that you will need to monitor the voltage and stop it when it reaches its “discharged” state without damage (depends on the battery chemistry).

108. #### Akshay Theertha

@Coleman Benson,
Yeah Thank you sir!

109. #### Akshay Theertha

Hi sir,
my small dc motor is running by a Li-Cd battery of 1.2V, 600mAh, current drawn by motor is 40mA.
soo 600mAh/40mA=15 hours,, soo it can run upto 9-10 hours.
And what i understood is if i connect that battery with another battery of 1.2v, 600mAh in paralell,,
then the Amp-Hours will be added ie. 1200mAh,,
soo now 1200mAh/40mA=30 hours, so motor can run upto 24-26 hours.,

Now What happens if i connect that both Batteries in Series,
then 1.2+1.2=2.4v and Capacity will be same 600mAh,

soo now 600mAh/40mA=15 hours,
which means the motor will run upto only 15 hours but with increase in Speed????

Thank you!

• #### Coleman Benson

@Akshay Theertha The effect of series / parallel is to either increase the capacity or the voltage. This is how battery packs are made. Remember, the theory is different than reality since discharge is not always linear as the battery voltage drops.