Batteries store electrical energy in the form of a charge. For most off-grid PV systems the battery bank is configured as 12 volts or 24 volts.
Batteries used for such systems are usually made up of either:
• 6 volt lead-acid batteries, common in electric golf cart applications
• 12 volt lead-acid batteries, such as deep-cycle/marine batteries
It’s important that all the batteries be of the same type and condition if possible. This improves both the safety and performance of the battery bank.