@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.
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…
@Agatha It’s an issue many people have encountered - the Pi# consumes ~1A at 5.0V (ideally via the micro USB). This means the best approach for a single battery solution is to opt for whatever nominal voltage your motors operate at and use a 5V regulator (and a USB breakout like https://www.robotshop.com/en/usb-type-a-female-breakout-board.html).
@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
@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.
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
@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.
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?
@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.
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?
@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 2.2x25 = 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).
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 ?
@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.
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
@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.
@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?
@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).
@Coleman Benson,
Yeah Thank you sir!
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!
@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.