Battery Question

Hi all,

I am very new to building robots and don't have much knowledge of electronics, apart from the basics many years ago at school.

However, I got an arduino at the weekend and have started doing experiments with it. I've just managed to take apart a cheap RC toy car and get the arduino to make it go backwards and forwards via a L293D motor driver and a very basic program. There are two motors in the car - the other one is a DC one attached to rack and pinion steering - I've not connected this to the other side of the L239D though yet.

I measured the voltage across the motor in the car before I took it apart and it was 4-5 volts (can't remember exactly what).

At the moment, I've got 4xAA rechargeable batteries connected to the L293D to power the motor. I'm using a separate battery to power the arduino.

I now want to use something a little better for the motor power. From what little I understand, the motor driver causes a voltage drop of 1.5v. Are there any recommendations for batteries? I've seen plenty of 7.2v RC battery packs with tamiya connectors but would this be too much? Alternatively I've seen a few 6 volt packs too.

Any recommendations to what's the best to spend my money on? I'd prefer to buy a battery/charger that can be used in my future robot projects.

Thanks in advance - sorry for the long post!


It would probably be helpful
It would probably be helpful to know how big the RC car is, but it’s likely to be ok to use a 7.2 volt RC pack. It is a bit bigger than 4 AA packs, as it is 6 C sized batteries put together. What was originally powering the car? My RC conversion robot used the orignal pack, which is a Tyco FLexpack, a 7.2 volt pack made of AA NiMh cells. On other robots, there has usually been 4 AA packs, one with a pair of 7.2 racing packs in parallel, and one with a couple of LiPo packs series for 14.4 volts. A charger I’ve felt was the best value was a Hobbico Quick Field Charger, that can handle NiCd, NiMh, and LiPo batteries, and charge 2 packs at once. It requries a 12 volt supply though. Something like this 12 volt power supply could be used.

Hi,Thanks for the reply -


Thanks for the reply - very useful information.

The car originally used 4 x AA batteries - its 1:15 - this one: . Thinking about it, when I measured the voltage across the motor (as the remote control joystick was on), it was around 4.5 volts, but I was using NiMH batteries, so the original supply voltage was 4x1.2 = 4.8 volts. So I think a supply voltage of 7.2v going through the L293D should be OK.

Thanks for the links, but I’m actually in the UK. I’ve also decided after reading your post that I can probably get away with using 6xAA NiMH batteries for the 7.2 volts to start with. I’ll maybe buy a decent battery & charger later.

Thanks for the help.