Solar Regulators

A solar regulator will prevent your batteries being over-charged. When a battery is "full" a means of tapering back or turning off the solar array is required. This is the function of the solar regulator or controller.

What is Available

Solar regulators come in four varieties:

1. Switching Regulators.
These regulators switch off the solar array at a predetermined voltage and turn it on again at another (lower) pre-determined voltage. These regulators are often referred to as simple regulators and are the most common small regulator type available. Once all regulators were switching devices however modern electronics have made PWM regulators affordable and reliable. The most economical regulator for small solar arrays is still switching regulator. Two stage switching is an improvement over the simple on off back on again at a lower voltage switch. What happens here is that when the frequency of on off switching slows right down (indicating that the battery is full) a new lower voltage switching level is selected. this results in lower water consumption and longer battery life. The simple "PR" series regulators we sell are of this type.

2. Pulse Width Modulated or PWM.
PWM control of solar current is more efficient than switching. Instead of your solar array being switched off at a pre-determined voltage, PWM type regulation will reduce panel current while maintaining a constant voltage at the battery terminal. A single constant voltage can still over-charge a battery bank so most modern PWM regulators actually provide an initial (high voltage) bulk or boost voltage. After a pre-determined time at this setting a further reduction in battery terminal voltage is initiated. The second lower voltage is called the float setting. The "PL" series regulators we sell are PWM type regulators.

3. Diversion Regulators.
Instead of switching off or reducing your array current a diversion regulator will divert unneeded panel current to another device, usually a heating element. This type of regulation is very efficient if you have a large solar array and want to extract all energy it provides. This type of regulation is often offered as an option on high current PWM solar regulators. This option is available on the "PL" series regulators we sell.

4. Maximum Power Point Tracking Regulators or MPPT
These regulators operate on the principle that a solar panel is at its power producing best at a variety of voltages and temperatures and therefore will deliver the most power into the battery when these parameters are met on the input side of the regulator.

In order to understand what is happening refer back the the first three types of regulators. All three have one thing in common; when the battery voltage is below the regulation voltage the panels are connected directly to the battery. When regulation voltage is reached the panel to battery connection is either broken or interrupted to reduce or eliminate the solar panel output. Connecting the panel to the battery is fine but automatically the voltage of the panel becomes the same (for all intents and purposes) as the battery voltage.

Check the typical spec of a solar panel:

It could look like this:

Peak power watts: 130
Peak power amps: 7.3
Voltage @ peak power: 17.4

Impressive?

Actually it is the spec "Voltage @ peak power" that the makers of MPPT chase and this figure varies according to cell temperature. If you run the panel at this voltage and then turn this voltage into what is required to charge the battery without linking the panel to battery you will get a substantial increase in panel output on most days. An even bigger advantage of using these MPPT thingies is that you can use a 24 volt panel on a 12 volt system or use a grid feed panel (32 odd volts usually) on a battery system.

Even more impressive you can wire all your modules up in series and feed the high voltage over a largish distance through thinner wire to the MPPT and have it convert this higher voltage to battery charging voltage with an impressive efficiency level. Typically you may choose a 48 volt or higher nominal array voltage for 12, 24 or 48 volt systems.

In a coldish climate a MPPT on an array of say about 450 watts or larger is simply too good a device to ignore. The benefits are huge and far outweigh the initial higher cost of these type of solar controllers. See our products pages for more details on these devices.

Calculating your regulator size:

Simply add up your panel wattage and divide by your system voltage at its maximum (full charge) level. For a 12 volt system this will be 15, for a 24 volt system this will be 30 and for a 48 volt system this will be 60 volts.

2 x 130 watt panels in a 12 volt system would need a regulator sized: 2 x 130 / 15 = 117.33 amp regulator.

If you are using an old regulator or a cheap and cheesy devise from a dubious manufacturer you are better off dividing the panel wattage by the nominal voltage ... 12, 24 or 48!

To calculate the rating for a MPPT is somewhat easier. You need to look at the spec sheet for the device in question. The manufacturer of the MPPT will state a maximum array size in watts and a maximum input voltage. Obviously you won't exceed this ...

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