Solar Ray !  The Most Reliable Name in Solar! Now serving Colorado, the Rockies, the South West, & beyond!

Power to the People!  Renewable Energy and Solar Power for Colorado, the Rockies, the American South West, and beyond!
SolarRay Power Boards
Official direct supplier of MidNite Solar products
Direct Supplier
of MidNite Solar
& wiring
Wiring Diagrams

BASIC BATTERY WIRING: how to connect batteries in series and parallel to get the right system voltage and amperage capacity.

A battery bank is a group of batteries wired together using series and/or parallel wiring.

A series connection is made by connecting one pair of opposite terminals of different batteries together (i.e. positive to negative). This increases the total voltage (the voltages of the two or more batteries are simply added together), while keeping the amperage capacity the same as just one of the batteries that are wired in series. Chances are you've been making series connections all your life -- flashlight batteries are put end to end, nose (+) to butt (-).
The diagram at lower right, below, shows 8 batteries connected together in series. This is one "string." Since these are 6V batteries, the nominal voltage of this string is 48V. If each battery is rated at 250AH, the AH capacity of the entire string is still just 250AH, since voltages, not amperages, add together in series wiring.

A parallel connection is made by connecting like terminals of two or more batteries together (i.e. positive to positive and negative to negative). This increases the amperage of the circuit (the AH capacities of the batteries, or strings of batteries, are simply added together) while keeping the total voltage the same as one of the batteries, or paralleled strings of batteries, in that bank.
The diagram at upper left shows two 12V batteries that are paralleled together. The total voltage of this battery bank is 12V. If each battery is rated at 250AH, the AH capacity of the battery bank is 500AH, since amperages, not voltages, add together in parallel wiring.

Often battery banks are connected together using both series and parallel wiring, as in the diagram at lower left, below. It shows eight batteries wired into two series strings of four batteries each. If they are 6V batteries of 250AH each, then each string has a voltage of 24V (6V x 4) and 250AH. The two series strings are then wired in parallel, which doubles the amperage capacity to 500AH, without changing the voltage.

Here, two 12V batteries are paralleled for the same voltage but double the amperage. Here, 6V batteries are wired two in series for 12 volts, then paralleled for more amperage.
Below, the voltage is increased by adding multiple batteries in series, with two strings in parallel for twice the amperage. Below, voltage is increased to 48 v by connecting eight 6 v batteries in series (8 x 6v = 48v ).

IMPORTANT: In parallel systems, always pull your main cables from opposite corners of the battery bank! (as in the above drawings)This way all the batteries are charged and discharged equally. Disappointing performance and premature battery failure await those that don't heed this simple rule.

Many other configurations are possible using the same series and parallel methods. We don't recommend more than 4 parallel sets of batteries in any configuration. Batteries can be series connected to very high voltages, some electric vehicles are wired for over 300 volts! For solar you need to match the batteries to your inverter and charge controller, which are almost always 12, 24, or 48 volts. Solar modules are wired similarly in series to get the correct voltage and paralleled to add current.

The batteries can also be oriented in different directions to fit tight spaces, but you may need longer jumpers. They can even be stacked on shelves, but leave enough room between shelves to add water to the batteries. Finally, make sure the battery jumper cables don't obstruct the watering caps. We sell cables that are just the right length for the job, too long and they'll get in the way, too short and..... you're not making the connection.