I have Duracell Ultra Power AAA batteries, current draw is around 2.5A when shorting for single unit.
I have just tried connecting them in series and parallel then measure discharge current.
Results:
-
Parallel: A bit increased current sourcing
-
Series: doubled current sourcing
It doesn't make sense if we think in terms of V=IR since series connection also increase internal resistance.
So my question is why? I doubt battery chemistry is the limiting parameter not the internal resistance ( maybe it is low enough?)
(BTW my end goal is to use 2 AA batteries to step up to 3.6V while supplying 2A for short bursts)
Best Answer
I think this is due to how you are measuring the current. Your results all make sense if the resistance of your current meter is higher than the internal resistance of the battery at the measured current.
Think of the limiting case where the batteries are pure voltage source (no resistance) and you put a fixed resistance accross them (your current meter in this case). Under these conditions, the current would be proportional to the total voltage, and you'd get pretty much what you measured.
The other limiting case is where each battery has a fixed finite internal resistance. This can be thought of as a resistance in series with a ideal battery. In this example, the "short" is truly a short of 0 Ohms. Now the short circuit current of any one battery is fixed, which is the battery voltage divided by its internal resistance. In this case adding any number of batteries in series won't change the short circuit current, but putting then in parallel multiplies the current by the number of batteries.
From your measurements, I think what is going on is close to case 1, not case 2.