Parallel 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 parallel wiring and series wiring. Either type of wiring may be implemented independently, or in conjunction with the other type. 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.
A very simple example of parallel wiring's affects can be seen when jump starting a car. The battery in the dead car remains 12-volts, and will still turn the starter, but only very slowly. Parallel wire a charged up 12-volt battery to the weak battery, and the dead car turns the starter at the required speed and the car starts immediately. Parallel wiring the charged battery to the weak battery did not alter the voltage – it remained a 12-volt system. The car's system is 12-volt, and running greater voltages through that system would be destructive to it. To avoid increasing the voltage and damaging the vehicle, the batteries are simply parallel wired.
Parallel wiring is quite easy and straightforward. (Please refer to Diagram 1) A wire of adequate gauge (1) is attached from the positive terminal on one battery to the positive terminal on the next battery. Likewise, a wire of adequate gauge is attached from the negative terminal on one battery to the negative terminal on the next battery.
In the diagram, our solar power battery bank has three 12-volt batteries that are parallel wired together. A 12-volt device may be powered off of any of the batteries. The last battery could also be connected to an inverter that changed the voltage from 12-volt to 110-volt. Thus allowing for the operation of 110-volt devices and appliances.
When you parallel wire batteries together, the length of time you can run electrical devices, of any voltage, depends on several factors including the amp hours available from the batteries and the power consumption rate of the devices. Naturally, the more batteries you have parallel wired together, the more power you will have for your electrical devices. The more batteries you have in your solar power or wind power battery bank, the more charging power (solar panels or wind generator) you'll require.
(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.