As you probably know, it is harmful to a lithium battery to charge it when it is at freezing temperature or below. That means 32F for us normal people…and 0 centigrade for those folks who don’t understand regular science and measurements.

Ok, ok…yes, I know that was pretty much rude and arrogant on the part of this American…typical…right!? But kinda funny from my perspective 😉

Back to lithium batteries…you can safely discharge lithium batteries slightly below 32F but you are not doing the batteries any favors. Charging lithium batteries at or below 32F can actually damage them. The lower the temp at which you try to charge it, the more damage is done…until you destroy it beyond recovery. So simply don’t do it.

However, in our area more and more folks are putting their solar equipment in CONEX containers or stand-alone, unheated sheds. And then winter rolls around, the temp inside the CONEX drops below freezing and they lose power. And then of course they are upset with someone…other than themselves. Why? Because they didn’t understand that most LifePO4 batteries, the good ones at least, have a temp sensor that will shut the battery down to prevent damage to the battery when the battery cells temp drop close to 32F.

And I have seen some real overcome projects come out of that…complex insulation boxes, propane heaters, heat lamps, etc. Ah, no need for all of that. And besides…a heat lamp uses an extraordinary amount of power…and that depletes your batteries pretty quickly during those long winter months.

So I did what many pros do…heat mats with thermostatically controlled outlets. Yup, that simple.

I looked on Amazon, and at my local hardware stone, looked for a high-quality thermostatically controlled outlet that turns on between 35F – 38F and turns of at 45F – 50F. I needed an outlet for each heating mat and a heating mat for between each set of batteries. Maybe consider a heating mat for the exposed side of each battery if they are in a block configuration.

If you are going to do this, the outlet units run from $15 – $26 or so for 1 – 3 outlets…just make sure you go for the best possible quality ones you can afford….you are protecting batteries worth thousands of dollars…you can afford quality outlets.

If you decide to do this, you can look at terrarium or seedling heating mats which run for $10 – $35. Or you can look at seedling heating mats as well which run about $12 – $18 each. Depending on how you have your batteries placed, you can place a mat between each two batteries, maybe one on the exposed side of batteries as well. Just make sure that the mat won’t overheat your battery. Batter should stay below 70F or so.

I would not place a mat over the face of a battery where there are terminals, wiring, controls, or displays.

Depending on your situation you might also need an insulated blanket over the batteries to keep the mat generated heat around the batteries. If that is the case I would suggest you move…you live in a far too cold environment 🙂

As with anytime you are working around electrical equipment, be very, very careful and follow all safety requirements and instructions. If you are hesitant or doubt your ability in any way…just call a qualified electrician or licensed solar installer. And naturally, you want to always follow recommendations and guidance from the battery manufacturer.

I am not a licensed electrician or a certified, licensed, bonded, or qualified solar system installer. The above information is not a recommendation or guidance for you to use in your system or with your equipment.

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