Dear Dave,
I have 300 watts of solar on my rig. I would like to use this solar-generated power in lieu of 120-volt shore power while I’m plugged into shore power. Does this occur automatically, or do I need to turn off the inverter somehow? Thanks. —Fermor, 2017 Coleman 185RB
Dear Fermor,
The solar panel provides a 12-volt charge to the house batteries through a controller. It does not provide any 120-volt power to the rig. You can only get 120-volt power through the inverter that takes 12-volt power from the house batteries and inverts it to 120-volt.
If you are connected to shoreline power, 120-volt power goes to the distribution center, which runs the 120-volt appliances through the circuit breakers and also to the converter or inverter/charger which charges your batteries. Most inverters do not power everything, just a few outlets like a residential refrigerator and maybe a TV.
How to tell what outlets are powered by inverter
You can tell what outlets are powered by the inverter using a non-contact voltage tester, which you can find on Amazon here. Unplug the unit, make sure the inverter is on and the battery or batteries are charged, then test the outlets for the refrigerator, TV, bedroom and other locations. This will tell you which outlets are powered by the inverter, and which are directly connected to the distribution center.
When you are plugged into shoreline power, the batteries are being charged by the converter or inverter/charger, and the solar controller should shut off so it does not overcharge your batteries. I would assume your rig has a converter to charge the batteries and the inverter is not an inverter/charger, as they are typically only used on bigger rigs.
The inverter typically has a pass-through feature that senses 120-volt power available so that power passes through to the outlets and the inverter does not operate. That would be the only “automatic” feature that I am aware of. No real advantage to using the solar panels when plugged in, that I can see.
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Dear Dave,
It seems my two 6v in-house batteries only charge through the solar controller. The battery voltage is fine during the day but they drain during the night while parked with no use. That occurs whether it’s plugged into shore power at 30 or 50 amps. I also plug into standard house power 115v at home to maintain the batteries, but it doesn’t work. Help. —Reno, 2022 Thor Magnitude BT36
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
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A reason to want solar power instead of shore power is if your shore power is being metered.
Wow, umm well Dave explained that pretty well. Maybe that guy should shut his engine off while going down hills? 300 watts ? Well that will run everything I’m sure? Maybe that guy is confused because he’s thinking of solar power used in residential applications where they are still hooked up to the grid as well as they don’t have a method of storage (batteries) so the grid kicks in, you know like at night.
My PSW Magnum Inverter is never turned off.
Thank you, Dave! I think that I understood your answer. 🙂 If so, then your patient instruction is bearing fruit. Thank you, have a great weekend, merry Christmas, and safe travels! 🙂