Solar and battery charging in winter (seattle)

Greetings, I am new to the forum, but have read a bunch of posts, so thanks for the good advice.

We have a 2017 Dodge Promaster. We bought it used, so I don’t know the specs on the solar/battery system, but we have 4 large solar panels on the roof. We bought in May and used it a ton all summer and while we were driving a bunch, it seemed like the battery meter was always near 100%, maybe dropping down to 80% overnight.

As the fall arrived in Seattle, we did not drive much, the days got shorter and darker. Welcome to the Seattle winter. Recently, I went out to the van. and the battery meter was down to 33%. I got in, drove around for 15-20 mins and it was back up to 66%, so the alternator charging works fine. But wondering if something is off with the solar system.


  • is it normal for this to happen in winter months, darker days? (We leave the small fridge running, at least for now)?
  • if so and we think the system is still working as designed, should I plan to drive it weekly to keep the battery at a higher charge rate?
  • Is there a % threshold at which point we might be really damaging the battery? I am happy to turn off the fridge too if that is going to make a big difference.

Thanks for all your advice

Yes, the lower sun and grey days definitely have a dampening effect on the solar. If it’s not a lithium battery and it’s below 50%, you’re damaging and shortening the life of the battery.

Clean the solar panels regularly with water and a squeegee if you have one.

What kind of fridge is it? We have a larger one and it only pulls ~1.2 amps. If you have four panels. (I am assuming they are 100 watts each. They should be if they are ~50x20 inches.) In my experience you should generate at least an amp or 3 even on overcast days. (We do with 3 x 100watt panels)

I don’t know if you need to drive it, there are other options. You could just get a cheap trickle charger or a promariner sport charger if it is not lithium and just keep it plugged in. We use this one and just leave it hooked to the system. If we run into a shady place where there is power it’s great and also allows us to get a solid charge from our generator if we need to use that to charge the batteries.

ProMariner 44012 ProSportHD…

You could always just turn off your electronics if needed including the fridge if you aren’t using them.

What kind of charge controller do you have? They aren’t all the same and some are certainly more efficient than others. We have a rover mppt and it tells us exactly what the solar is doing through a Bluetooth app. It’s expensive, but might be worth the upgrade for peace of mind and or trouble shooting the system.

Greetings & Welcome!

If it’s basically parked and you have shore power available, an automatic battery charger appropriate for your battery type would be a good solution. I’d also shut down the fridge when not in use.


"Always avoid complicated solutions to solve simple problems." ~ OffGrid