Series batteries are batteries that are installed end to end.
In other words, the positive terminal from one battery connects to the negative terminal of another battery.
When batteries are connected in series, the resulting output voltage is the sum of the battery voltages.
For example, two 12 volt batteries connected in series will provide an output voltage of 24 volts.
While output voltage will increase, the current capacity of batteries connected in series will remain the same.
Key Benefits to Series Batteries
There are two key benefits to installing batteries in series..
They provide more power for every amp of current supplied. For example the power supplied by a 12 volt battery providing 10 amp of current is 120 watts. Power on a 24 volt system providing 10 amps is 240 Watts.
This fundamental characteristic is what drives the design of many 24 Volt installations. Specifically smaller wire may be used when using a 24 Volt system and smaller wire costs less.
The watt hour rating is increased. This is due to a phenomenon known as Peukert’s law. This law states that as current supplied from a battery increases, the capacity decreases.
The reverse of this is also true. As current supplied from a battery decreases, capacity increases. Because it takes less current to supply power in a 24 system, the battery system capacity will increase.
Installation Considerations for Series Batteries
While installing batteries in series is not a complicated task, there are a few things that should be considered to ensure that the installation is safe and reliable.
Each battery should be of the same type and age when installed. Batteries of different types and age will have different energy storage capacity. What this means is that one battery will discharge faster than the other. When it comes time to charge the battery, each will charge at a different rate, thus there is a risk of damage due to overcharging and undercharging.
If there are devices that will make use of a 12 volt supply, a battery equalizer or a 24 Volt to 12 Volt converter should be use to ensure that both batteries are charged and discharged at the same rate.