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Postby willpearson » Mon Nov 20, 2017 6:38 pm

Hi - I'm about to buy my first pi! Planning a pi zero w + picon zero (probably) 2 wheel directional drive robot/car with a lego chassis. (adding sonar, camera, weapons? later)

I'd like to use a single rechargeable 4 x AA battery pack. I assume the 4.8v will do for the pi zero and the picon zero. But will I get into trouble with the motors? Could the wrong (too big) motors damage the boards by pulling too much current? Or will it just be that the pi resets as they run down? Any idea on run time - 5 mins or an hour+ ??

Any advice on the issue of power would be much appreciated,

Many thanks,

Will

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Postby Dave » Tue Nov 21, 2017 9:50 am

Unless your motor controller has dedicated power regulation for both Pi and Motors separately, it's highly recommend to power the Pi and Motors from different power sources due to the peak current that motors draw.

You might get away with 4.8v but you will likely get low power warnings on the Pi, but no chance if you intend to power both Pi and motors from the same battery pack.

How long the setup will last various dramatically on what batteries and motors you use. You can roughly work it out though:

Power for the Pi Zero W
Batteries: 2,500 mAh
Pi power consumption: ~ 200mA
Estimated run time ~ 12.5 hours (2500 / 200)

Do the same for the motors, I'll base it on the 3v motors we sell - https://www.modmypi.com/raspberry-pi/ro ... l-and-tyre

Power for Motors:
Batteries: 2,500 mAh
EACH motor power consumption: ~160mA
Estimated run time ~ 7.8 hours (2500 / (160*2))

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Postby willpearson » Tue Nov 21, 2017 3:05 pm

OK - thanks Dave. I'll look into 2 battery packs then. Maybe keep the 4 x AA for the motors. And I'll read more about running the pi from batteries. Quite tempted by 2 x CR2032 as I have a bunch of them at home and they're small. Need to read more about voltage regulation though eg. is it ok to use 6v (2 x 2032) without a ubec or similar? I'll keep learning...

Thanks though :) Ordered the pi and plenty of bits and bobs yesterday....

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