Originally Posted by nebulight
They have heating elements inside the battery. So you technically aren't charging below freezing, you are heating the batteries, then charging. I don't know much about them but I assume it will take the current from the charge source directly to the heating element, then once the battery is warm enough, it will connect the battery and allow a charge. If this is true, it's a great design as to not heat the batteries at night when solar is the primary charge source.
I missed this response initially on Relion and Zeravolt lithium batteries. If the heating element is built into the battery does it draw energy to heat the element from the batteries themselves? I take it solar is the primary source obviously if boondocking. Would not solar go through the battery itself to charge and then battery to heating element? I think you would have to have batteries inside a conditioned space with another heat source if the heating element of the battery is turned off at night. They would have to be shut down completely in long term storage and would have to be maintained above -4 deg. F. I doubt solar would do that in a northern climate.
I have a fairly large 800ah battery bank outside under my van and 10 watts total of electric resistant heating pads are sufficient to keep batteries above freezing and they are not on continuously as the batteries are maintained at 41 deg. F. With 800ah there is sufficient energy to power the heating pads off the batteries themselves. Solar, second alternator or shore power of course can charge the batteries at all times. The batteries will shut down completely at 20% SOC so absolute temperature of -4 deg. F. would then govern. Thus outside storage in Minnesota where I live would require shore power to store in the winter. Solar would be insufficient in the winter with low sun angles, shorter days, and cloudier days.
Underway on the road I have camped in overnight temperatures of -15 deg. F. and went a week straight under freezing temperatures 24/7 boondocking so have faith in my current system.
My new contemplated systems of 828ah LiFeMgPo4 batteries will withstand temperatures to -40 deg. F. so I could safely assume shutting down the batteries for winter storage outside could be done without shore power in Minnesota. They will be inside the cabin so conditioned space would maintain the batteries above freezing while underway. This is all now theory for me now that I have a belts and suspenders heated garage with shore power.