Can solar panels charge batteries in storage with disconnect applied?

Dear Dave,
My Riverstone has four six-volt batteries with one 100-watt solar panel on the roof. For the past three years, I had access to store our rig indoors with access to 110 v electricity to keep the batteries charged with a trickle charger. When doing this, I switched the main battery switch to “off” to avoid any battery drain. Now, unfortunately, I no longer have access to inside storage with electricity, so I must store my rig outside and depend on the 100-watt solar panel for keeping the four batteries charged.

My question is: When I turn the main battery switch to “off” to prevent battery drain, will the solar panel still act as a trickle charger to keep the batteries charged while in storage?

Our rig also has an Onan 5500 LP onboard generator, so if needed, I can also go out to the rig in storage periodically to exercise the generator. When doing so, if the main battery switch is “off,” will the operating generator still charge the batteries, or do I need to turn the switch to “on” to charge the batteries with the generator running? Thank you. —Greg, 2020 Riverstone 39RKFB

Dear Greg,
It depends on how your solar panel was wired, either directly to the batteries or through the converter. We installed a 100-watt panel on a 2003 Winnebago Brave as an aftermarket. We ran the cable down through the refrigerator vent on the roof and came through the side cabinet, as the converter was located under the kitchen cabinet right next to the refrigerator.

Installed controller under fridge

Then we installed the controller under the refrigerator as there was room to cut out a square and place it close to the connection. In this case, shutting off the main breaker at the distribution center would also turn off any voltage coming from the solar panel to the controller and through the converter as the shut-off switch is downstream of the converter.

We connected to the back of the converter as it was much closer to the cable coming down than the batteries, which were in the step compartment. The converter has a lug for positive and negative, so it was much easier than trying to get the cable through the cabinets and through the steel compartment of the entrance step.

Batteries in a fifth wheel in the front compartment

Since your unit is a 5th wheel, the batteries would be in the front compartment. If the solar panel was installed from the factory, it is most likely wired directly to the battery or batteries. This would allow you to shut off the main breaker at the distribution center and still charge the batteries with the solar panel.

The simple way to tell is to have the unit outside in the sun, unplugged and use a multimeter to see what voltage is at the battery with the disconnect engaged. If it reads 12.6 volts, the battery disconnect has shut off the voltage coming from the solar panel. If it is reading 13.2 volts or more, you are receiving a charge from the panel.

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I have solar panels to help charge the house batteries while boondocking, but after a couple of days the house batteries are dying. I turn on the engine to recharge the house batteries, but often it won’t charge them, even if I let the engine run for 15 minutes or more. Sometimes it charges as soon as I start the engine. What’s going on? —Brian, 2017 Leisure Travel Van (Unity)

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Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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