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A decent Pi UPS does exist

"Keeping a pi running won't matter to a car battery."

don't be so sure; the capacity of a car battery is only a few tens of amp-hours.

I recently bought a battery for my car that's rated at 55AH at 20 amps.

Drawing an average of 200ma for a few days can drain it completely, like maybe an RPi "left running". Yeah. This makes a few assumptions about how good your power conversion is (a switching 5V power supply will be more efficient than a linear regulator) but you get the idea:

200ma * 24 = 4.8AH ==> ~12 days for 55AH

Also you're really not supposed to go below 50% capacity on a car battery if you don't want to damage it. So make that "less than a week". Plus there's the "can I start my car when the capacity is that low" factor.

Reply to
Big Bad Bob
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Yep that's plenty assuming the car is driven say once a week. The OP was talking about use in a car not plugging the thing into an isolated car battery for weeks on end.

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Steve O'Hara-Smith                          |   Directable Mirror Arrays 
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Reply to
Ahem A Rivet's Shot

Coming soon ...

Reply to
Andy Burns

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