Asked — Edited

Which Battery Should I Use?

i am trying to create a mini wooden tank run by windshield wiper motors

i am going to control the motors with a bunch of servo switches and wanted to know if it's ok to power both the ez-b (connected to about 5-6 servos) and both motors with the same battery

if so

which one of these should i buy (is it ok to go over 5 -- i don't want the fuse to blow up)


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The 5A is too small. Windshield motors consume lots of power, especially when they are used with a heavy load. Try at least 7 or 8 A, if possible 2 pieces in parallel. Take my word for it... Good luck !


if i power both the motors and the ez-b (with multiple servos) to the same battery, will it effect performance for both

wouldn't it blow out the fuse for the ez-b if i go over 5amps


Go with 2 X 11.1 volt (2.2 amp) Lipo's. 1 for the EZ-B and your servos and 1 for a H-Bridge to run 2 motors. (you might also need a speed regulator to reduce the voltage to your Motors). You will also need a charger for the Lipos to balance them. I've had my completed robot Bob wizzing around the house on voice command for some time now and after trying everything, bang for buck, lightness and power they are an excellent choice.

2 x Lipos, 1 X speed controller, 1 x battery charger - (these items are not expensive, shop around or try my supplier.

  • Richies RC and Robotics at

Richies Robotics


wow! i am lost now, i know it has to be 12v but how many amps do i look for 5, 7, or 8

for the motors, i'm actually going to do this

am i going blow out the fuse if i connect the ez-b to something with over 5amps (i understand that i need at least 2-3 amps for ez-b because of the 5-6 servos)


The 11.1 volt (2.2 amp) will not hurt your EZ-B Board.. I don't think it would hurt to invest in a fan blowing over the board - espeically if your drawing power through to a bunch of servos coming off the board.

Good Luck



I'm using 2 power supplies for the EZ-B, one small battery pack for the EZ-B board and a 12V SLA for powering the motors. If you're connecting lots of servo's it's necessary to re-wire the cables and use a seperate power source for the servo's. You just need the PWM signal from the EZ-B to control the servo's. Show us some pic's, it sounds interesting.



A circuit will only draw as much current as is required for it to operate.

Individual loads such as L.E.D's draw a specific amount of current and will require you to limit the current through them by using components such as resistors. Google "L.E.D. calculators" to see what I mean.

With motors there are few things you should pay attention to. The first is operating current. This is the average amount of current the motor is expected to draw under a typical load or torque. Multiply this number by the rated voltage and you will get the average power draw required to run the motor. Motors can draw a whole lot of current for a split second when first energized. The other current rating which you need to pay attention to is the stall current. This is when you power up the motor, but you put enough torque on it to force it to stop rotating. This is the maximum amount of current the motor will ever draw, and hence the maximum amount of power too. So you must design all control circuitry capable of handling this stall current. Also, if you plan to constantly run your motor, or run it higher than the rated voltage, it is wise to heat sink your motor to keep the coils from melting.

See some of these links to help you understand.

Select the Right Battery for your Robot DC


A good electronics tutorial link is:


thanks rgordon (i'll look into that)

are any of you guys on (in case i have questions in the future)

@PhG --- i am rptech (the guy who posted that thread for the servo switch)

you can find me here --

the thread about wooden tank tracks is what i plan to modify, they didn't work at first so i'm going to turn it into mini wooden tank

just one last question (to everyone), if i do use two power sources, one for the two wiper motors and one for the ez-b with 5-6 servos and 2 sensors (no led)

what specifications do i look for in each battery (how many volts and how many amps) --- (no regulators or resistors and what not; just direct connection)

p.s. sorry for stretching this question (first time shopping uncommon batteries)


Do you have the wiper motor running amps and stall current specifications?(I assume they are 12v) Have you measured the motor resistance with an ohmmeter? Your choice of batteries and motor controller will depend on this info.

As for the EZ-B power requirements, see the ez-b Technical Manual. Once again it will depend also on how many servos you use and how much current they are rated for. Usually found on the servo data sheet.

EZ-B Tech Manual



cool pic's at instructables ! What I can advise for the use of wiper motors is hooking them up with a ESC to the EZ-B. I wrote about this a few times over here. They are easy to connect with external battery and you only need one port for each motor on the EZ-B.

Have a look at this:

ESC 12v-10/15A

and this thread from a while ago:

ESC motor control

Best regards,