24 volt solar regulators and wiring

A brief guide to solar regulators

If your solar array's power in Watts is more than 10% of your battery bank's capacity in Amp-hours, then a regulator is essential to prevent your batteries overheating and gassing.

In all cases, fitting a regulator will not only increase the amount of energy actually making it to your batteries, but will also help extend their lifespan.

Higher quality regulators will employ a sophisticated multi-stage pulse-width modulation (PWM) charging algorithms, designed to safely channel as much energy into your batteries as possible. All the 24 volt regulators we sell are of this higher quality type.

Many of our regultors also feature load terminals with automatic low-voltage disconnect (LVD). This will cut the power to your system should your battery level fall too low - ideal when connecting power-hungry appliances like 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 an MPPT regulator.

As a bonus, the MPPT regulator will also provide a potential 30% power boost to your system due to it's much higher efficiency.

These impressive devices work by constantly monitoring 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:

Wiring diagram conventional regulator

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:

Wiring diagram MPPT

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