Electronic – Batteries connected both in series and in parallel


I am confused.
Some sources say that connecting batteries in series also doubles the amperage (not only voltage) while maintaining the same mAh rating, while connecting them in parallel only increases the capacity mAh, while other sources say the amperage remains the same.

To put it simple, say I want to power an electrical motor that is 48V/1000W.
I will first need to connect 12 (3.7 hi-drain 20A 3000mAh li-ions) in series output 44.4V / 3000 mAh.
But since the motor drains 20.8Amps and 3000mAh means the battery can provide 3 Amps per hour, this essentially means the battery will get drained for what. 7 minutes? On max power.

This means I will also need to connect some batteries in parallel, to provide more capacity. So if I connect those 12 batteries in parallel with another battery.. does this make 14 minutes?

Edit, according to this, two batteries connected like that output 6A.
If measured separately they are 3A.

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Best Answer

"Some sources" are correct - but only in certain circumstances. If you are driving a fixed resistance, connecting two batteries in series will, in fact, double the current. Well, approximately. It won't be an exact doubling, since batteries have a volt/amp curve which produces less voltage for more current. For very low currents and some high-current battery chemistries, two batteries in series may come very close to twice the current.

For high currents, such as a level which will discharge the battery in 10 hours or less, you can count on a noticeably smaller capacity when the current is increased.

Conversely, to your specific situation, you've done the calculations correctly, and 7 minutes/14 minutes is about right. However, since each battery string is providing half the current when in parallel, you might reasonably expect greater run time. Like maybe 15 minutes instead of 14.

Your figure, on the other hand, makes no sense at all, and I have no idea where you got the idea.