Sciencemadness Discussion Board

What happens to capacities of batteries when connected in series or parallel?

AsocialSurvival - 8-11-2014 at 06:10

For example I have two Li-ion batteries, and I connect them in series to increase voltage.
What's going to happen to capacity of the overall capacity?
Does it increase, decrease, or stays the same (like of one)?
BTW, I am electrotechnician, and still have never understood this, very complicated.
Also, good if you know what happens to voltage and maximum current?

WGTR - 8-11-2014 at 07:18

Energy (volts x ampere-hours x 3600) of each cell is added together to determine the total energy (in Joules).

Voltages add together when cells are in series, ampere-hour capacities of each cell add when cells are in parallel. Otherwise the overall voltage and current ratings remain the same.

Energy (J) = voltage (V) x amperes (A) x time (seconds)

The internal resistance inside the cells add if cells are in series. This means that maximum current ratings remain the same in this case. If cells are in parallel, the maximum current ratings of each cell add together.

franklyn - 8-11-2014 at 23:03

Since a battery is also a resistor , the best most efficient use of
their combined rating is to drain them connected in parallel.

.

smokeup - 30-11-2014 at 07:55

Agree with franklyn. technically the capacity is the same, but when you put them in series you raise the voltage and if the load is the same in both cases you will drain the batteries down faster. On the other hand, if you want a brighter flashlight putting them in series is the way to go. (assuming the bulb can handle it)

unionised - 30-11-2014 at 08:52

Quote: Originally posted by franklyn  
Since a battery is also a resistor , the best most efficient use of
their combined rating is to drain them connected in parallel.

.


Unless it isn't.
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem