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Unread 08-08-2013, 10:56
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Re: Battery powered raspberry pi

Quote:
Originally Posted by Nathan4567a View Post
Ok. That is different. That way might not be legal like you said. I was just thinking of a couple if smaller capacitors in parallel to the input power. I have seen small capacitors like that on robots before. Would a small device like the raspberry pi even need a large bank like that though to stabilize the power? It seems like a lot for something so small.
Up to about 100uF (way less than even one super capacitor) you are not proposing something unusual.

What is required depends on how badly the power from the battery is being hammered. In a well designed fully operational robot the battery might never drop below 7V and 100uF would be just fine. Actually in that case even 10uF is more than enough.

However there is the not so unusual case of a robot with some design issues or damage that draws too much on the battery in random and unpleasant ways.

Then you get into the territory where you want storage of power segregated from the main battery. You can't do that with a small number of typical capacitors. You could store this kind of power in super capacitors. However then the design requirements go up.

With super capacitors it is possible to make a circuit that could have the robot battery pegged at 1V for 15 seconds and still provide power to the computing device like nothing unusual is going on. Why? Perhaps the extra computing device is monitoring that system or taking a hit like that will make that computing device do strange and unpredictable things that could complicate troubleshooting.

Last edited by techhelpbb : 08-08-2013 at 11:02.