How to replace a solar regulator

By: Philip Lord

Solar regulators are a pretty reliable component in a 12V RV solar setup. But, like any electrical component, they can fail. Follow our easy-to-follow replacement guide.

How to replace a solar regulator
Replacing a solar regulator in a 12V system can be done by anybody, but if you’re not confident with working on electrical systems, the work is best left to an expert

One reason for premature failure is if solar panels are added without taking into consideration the regulator’s capacity. The additional panel(s) can overload the solar regulator causing it to fail. The regulator also needs to be fitted in an environment where is doesn’t get too hot or, again, it can be prone to early failure.

Replacing a solar regulator in a 12V system can be done by anybody, but if you’re not confident with working on electrical systems, the work is best left to an expert.

What is a solar regulator?

So what exactly is a solar regulator? To understand what it does, you have to understand what the solar panel does. A 12V solar panel is designed to produce as much voltage as it can in the worst conditions, such as low sunlight and high temperatures. To charge a 12V battery the charging rate needs to be a minimum of 13.6V, so a solar panel is meant to attempt this. However, in ideal conditions, a solar panel can produce a lot more than this – sometimes more than 17V.

This is where the solar regulator comes in. The regulator is a component with solid-state circuits that is wired between a solar panel and a battery to regulate charge from the solar panel to the battery.

So the problem with this setup we’re looking at here is that the solar regulator failed, perhaps because it was an older unit. It no longer regulated the voltage from the solar panels, so was allowing a charge rate of up to 17V to go into the batteries. This caused the batteries’ electrolyte solution to boil, which irrevocably damaged the batteries. You can see in the second photo how the plastic battery casing has been warped because of the solution boiling.

The old regulator was an all-in-one unit, with a screen fitted in the cabin giving information on voltage inflow to the batteries. The new regulator, although more sophisticated, did not come with an information readout, and was to be fitted in the external battery compartment to allow better access to it for any future work. The new regulator was also much more bulky than the old unit, making hiding it behind the interior panelling more problematic. A separate readout screen and a shunt were also fitted.

A shunt is wired between the batteries and solar panels, and converts current inflow and outflow into a voltage signal. This voltage signal produced by the shunt (in milliamps) is reported to the readout panel, giving solar power inflow and battery system discharge info.

First off, the old regulator was removed from its mounting position within the RV. Then the 12V system control panel was removed to allow better access to the solar panel regulator wiring behind it.

The solar wires remaining in the cabin – those from the solar panels and those to the batteries – were joined. This was to save on wiring, because the joined wires would be disconnected from the batteries and become a direct feed from the solar panels to the new regulator instead.

Then the cable between the shunt and LCD readout panel was fed through from the cabin to the battery compartment. Now the shunt could be installed on the battery compartment wall, with the cable from the readout panel connected. The excess wiring was tidied up with cable ties and secured to the battery compartment wall.

Then the new lead-acid AGM batteries were installed in the compartment to replace the damaged ones.

The wiring to the solar regulator was plugged in to ensure it had good connections, and the regulator then secured to the battery compartment wall. An auto reset circuit breaker was installed between the regulator and the batteries.

Now, the power cables could be hooked up to the shunt and then the new LCD readout was plugged in. This new readout screen is much more sophisticated than the old one, giving information such as hours to empty calculated on power draw history.

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The full feature appeared in Caravan World #550 April 2016. Subscribe today for the latest caravan reviews and news every month!