24 volt solar regulators and wiring

A brief guide to solar regulators

If your solar panels (in watts) is more than 10% of your battery bank (in amp-hours) then a regulator is essential to prevent batteries gassing and over heating.

In all cases, using a regulator will not only get more energy into your batteries, but will also help to extend their life.

A good regulator will employ a sophisticated multi-stage PWM (pulse-width modulation) charging algorithms designed to get as much energy safely into your batteries as possible. All the 24 volt regulators we sell do.

Many also feature load terminals with automatic low-voltage disconnect (LDV). This will cut the power if your battery level falls too low - ideal for connecting power-hungry appliances such as fridges.

Conventional 24 volt regulators can only charge a 24V battery bank from 24V panels or 12V panels wired in series to produce 24 volts.

However, it is possible to charge your 24 volt batteries with almost any panel voltage using a MPPT regulator - plus they will get up to 30% more from your panels than a conventional regulator.

These cunning devices constantly monitor your solar panels and allow them to operate at their optimum voltage. Active solid-state transformers inside the regulator then step the voltage up or down to correctly charge the battery.

Why would you want to do this? Solar panels produce a lower voltage when they are hot. To allow for this, the manufacturers design them to produce more voltage than actually needed to charge batteries when they are cold (about 17.5V instead of 14V). Conventional regulators waste this extra power, but MPPT regulators can charge from any voltage and will harness more energy in cold conditions.

MPPT regulators can deal with higher input voltages than conventional regulators - 70V or even 100V is common. This means you can connect your panels in series with the benefit of producing enough voltage to charge your batteries even in dim conditions.

Finally, when selecting a regulator make sure it is large enough to handle all the solar panels you have, or plan to have in the future. It's best to oversize now than have to buy a larger one later on.

Wiring

It is important to use the correct cable to wire up your panels - it needs to be sufficiently thick and if it is exposed to the element it must be outdoor rated.

See our information page on wiring 24V systems for help on selecting the appropriate cables.

A wide range of cable including FlexSolar outdoor-rated solar cable is available from our sister company Midsummer Energy.

The way you connect up the panels and regulator depends on whether you are using a conventional or MPPT regulator.

With a conventional regulator, the panels will need to be wired in pairs to produce the necessary 24V. These pairs can then be wired in series to provide the required total output power.

Here is an example:

If you have an MPPT regulator, the panels are better wired in series up to the maximum voltage specified by the regulator. This will provide greater total energy, and also means lighter wiring is needed:

These two schemes will produce about the same total energy even though the first has a whole extra panel!