Powering equipment via batteries often means connecting them together in a battery bank to gain a higher voltage or amp hour rating.
Batteries can be connected in two ways, series or parallel.
Series
Connecting two batteries of the same voltage together in series effectively converts them into one bigger battery doubling the voltage rating of the battery bank, but keeping the same amp hour rating.
e.g. Connecting two 6 volt 30 Ah batteries together in series, will give you one big 12 v battery with a 30 Ah rating.
Connecting three together in series will give you an 18 volt battery with a 30 Ah rating.
Below is an example using 3 x 12 volt batteries with 100 Ah ratings.
Connecting In Parallel
When connecting batteries of the same voltage and amp hour rating together in parallel, the amp hour ratings of the batteries are added together, and the voltage across them stays the same as an individual battery.
e.g Three 12 volt 100 amp hour batteries connected in parallel would give us one large battery bank of 12 volts and 300 amp hours.
As you can see, both circuits still kick out the same amount of power – 3600 w.
As the equation for power P = VI shows, connecting in series or parallel affects the voltage and current ratings across each circuit. They are inversely proportional to each other.
Be aware when connecting batteries together in packs. It is always advised to connect batteries with the same voltage and amp hour ratings together so as to keep their voltages and rates of discharge as even as possible. This avoids voltage drops across one battery affecting the others, prevents strain on the pack, improves battery life and and keeps the system balanced.
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