Hm, I have an issue my the Solar node. It heats up too much in the sun. The panel getting hot might be one thing but the inside of the box where the batteries are? That worries me.
I installed a BME280 so it sits inside the box and the temperature reading is actually quite helpful here. I pulled the plug when it got to 55C within hours.
Has anybody experienced that? Isn’t that a problem for the batteries? I don’t need this exploding!!
It was this past winter, but I’m at a pretty low latitude (~31.8°). The SenseCap Solar P1 has a huge 5w panel. I run a Meshcore repeater, also NRF52-based, under the same eaves with only a 1w panel. It stayed up all winter, too.
Yeah, that’s much closer to the equator than I am. While this would work for me in the summer it may not in the winter - when temperatures drop well below 0 degrees Celsius (making charging less effective) , and the sun does not shine for that long (shortening the charging time significantly).
Paradoxically, solar panels perform better in the cold , at least on MPPT controllers. It won’t make a practical difference in your scenario but it’s interesting. At least to geeks like me.
But I believe you shouldn’t charge batteries in very cold conditions (below -10C?)
Yeah, both Li-NMC and LiFePO4 can be damaged by charging when cell temps are below freezing. There is some anecdotal evidence that the very low C (current) rates we see with small panels could make it a non-issue. One of my nodes was up over last winter and froze a few times. I haven’t observed any capacity reduction although TBF I didn’t do any actual capacity tests.
In my campervan where I have a 380Ah LFP bank I use warming pads to keep the cells at human-comfortable temps.