To connect a group of batteries in series, you connect the negative terminal of one battery to the positive terminals of another, and so on until all batteries are connected.

Wiring batteries together in series will increase the voltage while keeping the amp hour capacity the same.

For example:

2 x 12V 100Ah batteries wired in series will give you 24V, but only 100Ah capacity.(24V*100AH=2400WH=2.4kwh)

When connecting batteries in a parallel, the negative terminal of one battery is connected to the negative terminal of the next and so on through the string of batteries.

Wiring batteries together in parallel has the effect of doubling capacity while keeping the voltage the same.

For example:

2 x 12V 100Ah batteries wired in parallel will give you only 12V, but increases capacity to 200Ah. (12V*200AH=2400WH=2.4kwh)

Series-parallel connection is when you connect a string of batteries to increase both the voltage and capacity of the battery system.

This is a combination of the above methods and is used for 2V, 6V or 12V batteries to achieve both a higher system voltage and capacity.

For example:

4 x 12V 100Ah batteries can be wired in series /parallel to give you 24V with 200Ah capacity. (24V*200AH=4800WH=4.8kwh)