So I have a small solar setup (100w/200ah) in my camper van. I left the controller/panel/batteries hooked up thinking I would occasionally clear the snow and there would let the sun topped the batteries off. However, we had an extreme amount of snowfall this year, while all my focus was on keeping the roof & driveway clear, I pretty much neglected the van all winter.

I just cleared the 4 feet of snow off the top (I know this weight is horrible for the panel) and sure enough, I can't seem to get the controller to charge.

The controller is reading ~21v from the panel but no amps. I tested the amps with a multimeter and the panel is surprisingly still generating ~90w (about as good as ever).

The batteries however, are not in good of shape... They are currently reading ~9.8v. I realize that these batteries are probably ruined, but I just want to make sure I properly diagnose the problem before I go and buy new equipment.

I thinking one of two things might be happening:

  1. The charge controller (EPEVER 20A MPPT) is broken :(
  2. There is some low voltage protection on the charge controller that prevents it from charging if a battery doesn't meet a given voltage. I'm actually a little surprised that the display comes up at all with only 9.8v

Just looking for advice on where to go from here.

If I get my batteries back up to operating voltage, is there a chance the controller will kick on? Or should I just go ahead and bit the bullet and order a new battery. Also, could I test the charge functionality on the van starter battery to confirm that the charge controller isn't the issue?

  • Hi and welcome! Can you provide some more detail on the battery, such as the type/chemistry, model, brand, etc? I suspect that the batteries slowly drained to a voltage below the charge controller cut off. You could try boosting them back up with a trickle charger plugged in to a standard outlet, but if they are damaged the voltage may simply collapse again.
    – LShaver
    Mar 25, 2019 at 20:44
  • @LShaver the bank made up of 2 100ah 12v sealed AGM batteries in parallel. One was purchased 2 years ago and was previously in decent shape. The other is about 5 years old now and should probably just be removed from the bank
    – NSjonas
    Mar 25, 2019 at 21:26
  • and ya, I've got a trickle charger (Battery Tender brand), but unfortunately the van is parked about 150ft from the nearest outlet. I just need to buy longer EXT cord.
    – NSjonas
    Mar 25, 2019 at 21:30
  • I was about to write an answer but something fishy is going on here... the controller shows now current, but you're measuring current from the panels? Where is that current going? Are there loads connected in the van?
    – LShaver
    Mar 26, 2019 at 13:53
  • 1
    It sounds like the panel and charger are fine, but the batteries dropped below low voltage threshold of the charger, so they're no longer charging them. I'd try connecting them to your trickle charger.
    – LShaver
    Mar 26, 2019 at 18:46

1 Answer 1


Just wanted to post an answer to close this one out.

Turns out the panel and controller are fine. I attached a trickle charger and got the batteries back up to ~11v and then reconnected the solar and it kicked on!

There must have just been a low voltage threshold where my charge controller stopped charging (even though it was still within the controllers operating >9v).

  • That batteries probably are toast anyway, fwiw. Lead-acid left sitting at 9.8v for any amount of time is going to mean serious sulfation. In this case, the effective capacity of the batteries is now greatly reduced. They will appear to charge quickly and then discharge just as quickly. There are folk tales about how to reverse sulfation damage but no proven methods. 11.9v is generally accepted as 100% discharged, for what it's worth. Mar 28, 2019 at 16:57
  • @Jean-PaulCalderone ya I've read a little about it. I'll probably pick up new batteries eventual but for now they will work. Mostly these just run some LED's and a vent fan.
    – NSjonas
    Mar 28, 2019 at 17:01

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