Series Wiring of Batteries
by Damien Andrews
If you are contemplating a sustainable energy system such as solar power or wind power, then you are most likely going to need to understand some basics about wiring batteries. Batteries are an important part of almost all solar power and wind power systems. Without batteries connected to your solar powered sustainable energy system, you will have no power during darkness, and reduced power during early morning, evening, and cloudy days. With a wind power system, if you don't have batteries then your power will drop when the wind lessens, and your power will quit when the wind drops below the starting speed of your wind power system – usually around 7-mph. Batteries allow you to store energy for use when your wind power or solar power systems don't create electricity.
The two types of wiring that are most relevant to setting up a battery bank for a wind power or solar power system are series wiring and parallel wiring. Either type of wiring may be implemented independently, or in conjunction with the other type. Series wiring batteries together allows you to increase the voltage available for electrical devices and appliances. Parallel wiring allows you to link more batteries together without changing the voltage, thus providing additional power when it's needed by your appliances and electrical devices.
Series wiring batteries together is simple and straightforward. (Please refer to Diagram 1) A wire of adequate gauge (1) is attached from the positive terminal on one battery to the negative terminal on the next battery. Likewise, a wire of adequate gauge (1) is attached from the negative terminal on one battery to the positive terminal on the next battery.
In the diagram, our solar power battery bank has two 12-volt batteries that are series wired together. A 24-volt device may be powered off of the battery at the end of the series, unlike parallel wiring which allows the use of any battery in the bank. The last battery could also be connected to an inverter that changed the voltage from 24-volt to 110-volt. This will allow for the operation of electrical devices running on 110-volt.
The more batteries you wire together in series, the greater the voltage. A popular voltage for larger, off-grid solar power and wind power systems is 48-volts. This requires that four 12-volt batteries be wired in series. Of course, you could also use batteries of other voltages, and series wire together enough of them to equal 48-volts total. For example, if you want to use 6-volt batteries in your solar power and/or wind power system battery bank, you will need to have eight batteries in the bank.
While series wiring increases the available voltage, it does not increase the available amount of electricity available. You can add more available electricity to your battery bank by series wiring AND parallel wiring to achieve the desired amount of available electricity in the desired voltage.
(1) The greater the distance electricity must travel along a wire, the greater the wire's gauge (size) must be to minimize loss of power. Hence, if you place your batteries 10 feet apart, you will need to have heavier gauge wires running between them than if you placed the 1 foot apart. Heavier gauge wires are more costly. In some wind power and solar power battery systems, some of the batteries may necessarily be several feet apart, but battery banks and shelves should be designed to minimize the distance between batteries, without creating excessive heat.