# Battery help please

Hi everyone,

I’m about to embark on a walking robot using a mini maestro 24. It will be a quardruped, with 3 medium servos controlling each leg. I will make it pretty lightweight but before construction I’m going to buy the mini maestro unit and run some tests with servos.

I’d like some advice on batteries please! I’ve been thinking about getting one of the battery packs from pololu, one that runs at 4.8 volts with inbuilt switch. Would this be sufficient, and would I need anything else to connect up to the controller… IE resistor? Also, could I run more than one pack in parallel to increase battery life?

Sorry for the extremely beginner level questions, electronics are not my forte!

Servos consume a lot of current – allow about 1 ampere for each straining servo. Assuming that only one leg of the robot will be moving at a time, you will probably need a battery pack capable of supplying 1-2 amperes continuously at 4.8 to 6 V.

Divide that current draw into the battery capacity (in ampere hours, Ah) to get a rough estimate of battery life. If the battery capacity is given in mAh, divide the given figure by 1000 to get Ah.

It is always a good idea to power servos and motors separately from any controlling electronics, but be sure to connect the grounds together.

Thanks very much for the response. How would I power the servos separately? - don’t they all run into the maestro? Or would I just wire the signal cable to the maestro ?

Follow these instructions for wiring separate power supplies to the Maestro: pololu.com/docs/0J40/7.a

Likewise, any controlling microprocessor should be powered separately from the motors.

Great, thanks. Perhaps should have looked here sooner. The power supply to the Maestro says from 5-16 volts. How should I work that out? Could I just use a 9v block battery?

Hello.

You could use a 9V battery to power the processor on the Maestro. (Just be sure to use a more appropriate supply for servo power, like Jim mentioned.)

By the way, I recommend reading this blog post, which explains battery capacity:

pololu.com/blog/2/understand … h-is-not-a

- Amanda

Perfect, thanks very much for your help