Connecting batteries in series increases the amount of voltage. It doesn’t increase the ampere capacity. For example, if you connect two 4S 14.8V 9500mAh batteries in series, you get a combined voltage of 8S 29.6V. The capacity, 9.5 amp hours (Ah), stays the same.
Before you connect batteries in series, make sure they have the same voltage and capacity rating. Mixing and matching is ok for your closet.
How to Connect RC Batteries in Parallel
So what’s the main difference between putting your RC batteries in series vs. parallel? Connecting in series increases voltage, but wiring in parallel increases battery capacity. The total voltage doesn’t change.This means that two 6200mAh 7.4V 2S shorty lipo batteries in parallel would give you a total capacity of 12400mAh.Voltage stays at 7.4 volts.Like wiring batteries in series, there’s no mixing and matching allowed. All batteries in parallel must have the same voltage and capacity.