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 Living on the Road :: Articles :: Batteries, serial & parallel

NOTE: This article was printed in the July Wanderer magazine, unfortunately someone stuffed up and two of the illustrations were identical. This is the original version.


Many smaller motor homes need only one house battery, however those with larger power requirements need multiple batteries connected in series, parallel or some combination of both.

So what is this series/parallel?

Series = more volts, same current
A series connection is one where the POS terminal of one battery is connected to the NEG of another resulting in a single battery "bank" with twice (or more according to the number of batteries) the voltage and the same current capacity as a single battery.

The following example shows four 6V 100AH batteries connected in series to make a single 24V 100AH battery bank.


Fig 1.


Parallel = more current, same volts
A parallel connection is one where the POS terminal of one battery is connected to the POS of another and the NEG terminal of one battery is connected to the NEG of the other.

This arrangement creates a battery bank with the same voltage of a single battery with twice (or more according to the number of batteries) the current capacity.

In the following example shows four 6V 100AH batteries connected in parallel to make a battery bank of only 6V but 400AH current.


Fig 2.

So what if you need both more voltage and more current? You simply add batteries in series and/or parallel to arrive at the combination of voltage and current you require.

The following example shows four 6V 100AH series banks connected in parallel to form a single bank of 24V 400AH.


Fig 3.

Or how about four parallel banks in series.


Fig 4.

The electrical output is the same in the two above examples, often the choice is based on practical considerations like the physical placement of the batteries.

In Fig 3 only the red and blue wires need to carry 400A (the grey wires each carry 100A) whereas all wires in Fig 4 have to carry the full current (this is a generalisation, in both cases the actual current carried by each wire would depend on the exact physical placement of each wire).

This would usually make Fig 3 the more practical method to achieve 24V at 400A.

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