Updated October 2020

Interconnecting Batteries

Interconnecting batteries in series or parallel is feasible but you need to know how it works. And its limitations. Interconnecting your batteries in series increases the voltage. Your current remains as before. Interconnecting your batteries in parallel increases the current. Your voltage remains as before. No matter how connected, your stored energy remains the same.

Batteries consist of cells (each of about two volts when fully charged). A 12-volt battery has six such cells. The cells are connected end-to-end.

Series connection increases battery voltage. Most car and travel trailer batteries are twelve volts. Some big motorhomes, however, have 24-volt systems. These typically have two 12-volt batteries in series. Many large solar systems use 48-volt storage - of banks of four 12-volt batteries in series.

Parallel connection increases battery capacity (i.e. the amount of energy it can store). It is often used to limit individual battery weight. For example, a 12-volt 240 amp-hour lead-acid battery weighs about 65 kg (145 lb). To ease handling, it's common to parallel-connect two 12-volt deep-cycle 120 amp-hour batteries.

Large solar systems typically parallel-connect banks of four 12-volt batteries to store energy at 48 volts.

Battery shed coconut well reduced jpg

That shown above is a bank of 16 batteries (each of 12-volt). They are connected in series/parallel. This provides 48 volts at approximately 960 amp-hours. Pic: author's previous all solar house north of Broome.

Interconnecting batteries in series or parallel - the pros and cons

Each way of interconnecting has advantages and disadvantages. These, however, are not the same advantages and disadvantages. Nevertheless, if you need over twelve volts, and/or substantial capacity, you must increase voltage, current or both.

batteries series (6-12 volt)

Batteries - series connection

Connecting two batteries end-to-end results in the total voltage being the sum of each battery. The available current and voltage are that of the 'weakest' cell. read more...