Morning all – A couple of months ago, I fitted a 200W solar panel coupled with two new AGM batteries and a 100/20 MPPT to my campervan. We’ve had a good summer with consistent warm, sunny weather. Everything was going well initially, always maintaining a good charge, but when I picked it up after it had been in storage for a couple of weeks, the leisure batteries were flat. I have checked the app, and it seems there has been a significant drop-off in charging. Hoping someone may be able to help. Thanks.
Looking at the above, the system has been charging every day, but charging much less than what is being used every day so the battery was getting more and more depleted. I note that the solar voltage is also lower.
A few thoughts on reduced solar, the position of the sun changing has meant that the panels are now partially or fully shaded or someone parked a tall van next to yours, or they have got dirty from say lost of bird droppings if the van is parked near a pigeon / seagull roost, the wiring on the solar panel to the MPPT has developed a high resistance so not as much power is getting through, something has fallen on the panel damaging it. The latter 2 points will need a multimeter to really test if there is an issue here.
Then there is the obvious case that a load has been left on which is larger than the solar can maintain. A final thought is a battery failure and a shorted cell in one of the batteries resulting in a high leakage current which would manifest the same as an unexpected load. You can not tell this from just the voltage plots. Also look at the yield history every day and the battery current, if these remain the same as normal then it is a load or battery issue.
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