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Batteries in Series & Parallel

If you have more than one battery you will need to wire them together either in series or parallel or a combination of series and parallel. When you wire the batteries in series the voltage of each battery in the group is added together but the amps are not. When you wire batteries in parallel the amps of each battery is added together but the volts are not. Separate groups of batteries wired in series can also be wired together in parallel. (More on this below) In either case the watts will always remain the same. Remember, volts x amps = watts.

Batteries in Series

When you wire the batteries in series the volts will increase but the amps will stay the same. In the illustration we have three 12-volt 100-amp hour batteries wired in series. To get the combined voltage simply add the voltage of the three batteries. 12v + 12v + 12v = 36 volts. The amps will remain the same. 100ah. You will only wire the batteries in series if you need to increase the voltage. If you have two 6-volt golf cart batteries and you want to run 12-volt appliances, you will need to wire them in series to produce 12 volts.

Batteries in Parallel

When you wire the batteries in parallel the amps will increase but the volts will remain the same. Adding the amps of the three batteries gives you the amperage of the battery bank. 100ah + 100ah + 100ah = 300ah. You will have a 300ah 12-volt battery bank. You will always wire the batteries in parallel if you do not want to increase the voltage. If you wish to run 12-volt appliances off this battery bank it is much easier to keep the voltage at 12 volts by wiring the batteries in parallel than reducing the higher voltage from a bank wired in series.

Batteries in Series & Parallel

You will only wire the batteries in series and parallel if you want to increase the voltage, but not as much as you will get by wiring all the batteries in series.   What we must do here is wire two separate groups of three batteries in series, then wire the two groups together in parallel. Each group of three batteries in series will become 36 volts 100-amp hours, as the voltage in series add up but the amps do not. When we wire the two groups in parallel the amps add up, but the volts do not. So, we end up with 36 volts 200ah.


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Series and Parallel