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Fr Robert Ballecer, SJ - Hey Padre and Bryan Great Pi Day episode!


G+_Tom Apalenek
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Fr. Robert Ballecer, SJ - Hey Padre and Bryan. Great Pi Day episode!

But you had a little oopsy when you were going over the battery power formulas. You stated that with a 30C LiPo battery you could safely draw 30 Amps from the battery. That's not quite right.

The 'C' in 30C stands for Capacity and refers to the capacity of the battery in amp-hrs. So the maximum power draw from the battery is 30 times the capacity of the battery in amp-hours (dropping the hours part).

So for the 5300mah (5.3 Amp-hour) battery that you used in the example, the maximum safe current draw from the battery is 30 x 5.3 or 159 Amps, not 30 amps.

That makes a big difference in how much power you can get out of the battery and how fast you'll drain it.

So the maximum power out of that 11.1V battery is theoretically about 1,765 watts. At that maximum power, a fully charged battery would be completely drained in 2 minutes.

Of course the realistic power capability will be less than that because the terminal voltage is going to drop by probably a volt or more if you draw 159 amps from the battery, but that's a entirely separate discussion.

The rest of your estimates based on how much he actually would draw with his 100W LED looked pretty good.

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