One of the issues operators have with remote solar powered anything and lithium batteries is cold weather.
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They don't like to be charged at below freezing temperatures.
Thanks to another user I discovered a possible method of preventing battery damage using a Thermal reed switch.
It appears to be a normal magnetic operated reed switch with a substance called Thermorite orientated as a magnet.
According to the spec sheet, Thermorite is a ferromagnetic substance who's magnetism decreases with rising temperature.
Depending on the recipe, it can be made to operate at specified temperatures.
I've ordered one to switch open at freezing (0C).?
It will be in contact with the lithium battery and the switch in series with the 5W solar panel. Specs say it can handle 10W.
Anytime the battery is too cold, no charging will occur.
If it works out, the next thing will be to see how much storage I need to get thru the sunless days.
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Here's a link to the data sheet. Digikey carries them. Not cheap at $30 ea.
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73
Mike N0QBH
N0QBH Mike Berg