With thanks to Branden Austen of Deltec Energy Solutions
There are three types of wiring configurations that are relatively easy to learn. Once these are mastered, the wiring of batteries or solar modules becomes easy as pie.
The three configurations are:
- Series Wiring
- Parallel Wiring
- A combination of the two known as series/parallel wiring
In any DC-generating device such as a battery or solar module, you will always have a negative (-) terminal and a positive (+) terminal. Electrons (or current) flow from the negative terminal through a load to the positive terminal. For ease of explanation, we shall refer to a solar module or battery as a “Device”.
To wire any device in series, you must connect the positive terminal of one device to the negative terminal of the next device.
It is important to know that, when you wire devices in series, the individual voltage of each device is additive. In other words, if each device in the above example had the potential of producing 12 volts, then 12 + 12 + 12 +12 = 48 volts. If these devices were batteries, then the total voltage of the battery pack would be 48 volts. If they were solar modules that produced 17 Volts each, then the total voltage of the solar array would be 48 volts.
The second important rule to remember about series circuits is that the current or amperage in a series circuit stays the same. So, if these devices were batteries, and each battery had a rating of 12 Volts @ 220 Amp hours, then the total value of this series circuit would be 48 Volts @ 220 Amp hours. If they were solar modules and each solar module had a rating of 17 volts and were rated at 5 amps each, then the total circuit value would be 68 volts @ 5 amps.
In this example, two 6 Volt 350 Amp hour batteries were wired in series, which yields 6 Volts ÷ 6 Volts = 12 Volts @ 350 Amp hours.
If the devices in the example above were solar modules which were rated at 17 volts each @ 4.4 amps, then this series circuit would yield 34 volts at 4.4 amps.
Remember that the Voltage in a series circuit is additive and that the Current stays the same.
To wire any device in parallel, you must connect the positive terminal of the first device to the positive terminal of the next device, and the negative terminal of the first device to the negative terminal of the next device.
Important: When you wire devices in parallel, the resulting Voltage and Current is just the opposite of a series circuit. The Voltage in a parallel circuit stays the same, and the Current is additive. If each device in the example to the left had the potential of producing 350 Amp hours, then 350 + 350 = 700 Amp hours, but the Voltage would stay the same.
If these devices were batteries, then this parallel circuit would yield a total voltage of 12 volts @ 700 Amp hours. If these devices were solar modules that produced 17 Volts @ 4.4 amps each, then this parallel circuit would yield 17 Volts @ 8.8 amps.
In the example on the right, four 17 Volt @ 4.4 amp solar panels are wired in parallel, which yields 4.4 Amps + 4.4 Amps + 4.4 Amps + 4.4 Amps = 17.6 Amps total @ 17 volts.
If the devices in the example were batteries which were rated at 12 volts each @ 220 Amps, then this parallel circuit would yield 12 volts @ 880 Amp hours.
Remember the Voltage in a parallel circuit stays the same and the Current is additive.
Hold on to your hats, because here’s where it gets a little wild. Actually, you’ve already learned all you need to know to understand series/parallel circuits.
A series/parallel circuit is simply two or more series circuits that are wired together in parallel.
In the example pictured, two separate pairs of 6 Volt batteries have been wired in series and each of these series pairs has been wired together in parallel.
You might be asking why in the world someone would want to put themselves through this. Well, let’s suppose that you want to increase the Amp hour rating of a battery pack so that you can run your appliances longer, but you need to wire the pack in such a way as to keep the battery pack at 12 volts. Or you want to increase the charging capacity of your solar array, but you need to wire the solar modules in a way that will keep the solar array at 34 volts… Well, series/parallel is the only way to do either of those.
In parallel circuits, the current is additive, and thus you increase your run time or Amp hour capacity; or, in the case of solar modules, you increase your charging current by wiring the batteries or solar modules in parallel.
Since we need 12 volts but have 6 volt batteries (or, in the case of solar modules, we need 34 volts and have 17 volt modules on hand), wiring the batteries or solar modules in series allow us to get the 12 volts or 34 volts that we need.
An easy way to visualise this would be to start by wiring the batteries in individual sets that will give you the voltage that you need. Let’s say that you need 24 volts but have six volt batteries on hand. First wire four of the batteries in series to get 24 volts (wire in series to increase voltage) and continue to wire additional sets of four batteries until the batteries are used up.
Next, wire each series set of four batteries in parallel to each other (positive to positive and so on, and then negative to negative and so on) until each series set is wired together in parallel. If each series set of batteries equals 24 volts at 350 Amp hours, then five series sets wired to each other in parallel would give you a 24 volt @ 1750 Amp-hour battery pack.