Heat pad

[HRTKD]

I prefer battery warmers that are specific to batteries, not a tank heater. I buy mine from UltraHeat. They're expensive, but I trust them better than the other options. You'll need a separate thermostat, one for each battery unless you're going to heat an enclosure instead of individual batteries.

Easiest thing to do may be to find an old cooler and make that your battery box. Then heat the enclosure. Additional insulation may be needed unless you're using a Yeti cooler.

 

[FishHog]

They are fine being cold. Just can’t charge when cold. May shutoff at -20C however. So they might take a while to warm up when/if you arrive and they are that cold. If you don’t arrive in the dark at below -20, just use them until they are warm enough and turn your solar on after that.

 

[DPC]

We run 6 led lights and charge phones. Nothing more.

Probably enough....

Lead acid batteries would probably be just fine too....
Years and years I ran lights a black and white TV from a couple 12 volt deep cycle batteries .
The trick was to keep the discharge cycles short and battery charged.
Also used an 3 hp Briggs and Stratton flat head and 60 amp Chrysler alternator with a an adjustable regulator to charge until a 20 watt solar was installed in 1990.....

 

[outboard1196]

So it’s looking like not cost effective to return the batteries in Amazon. What else will I need to make this work ? 600watts of panels ? Heated box ? These batteries live inside the cabin. But I only go to camp 4-5 times in winter. I don’t go -30. My son is there tonight. It was -35c , the batteries will be alone there weeks on end. I need a safe system. I’m worried about heating sewer pads running under batteries. Cabin is 2 hours NE of Thunder Bay Ontario. Near top of Lake Superior.

Any chance you have a victron charger or some sort of programmable relay? You could set it so the heater pads only run when the sun in up. The battery will hold enough heat over night.

 

[SunDave]

Depending on budget, another option would be to use the lithium somewhere else, and use lead acid instead of fighting it. In 10 years extreme cold may not be a problem for batteries anymore, but it still is now. This level of cold is a whole different ball game than most people are used to. It's not just dipping below freezing at night. It's cold soaking the batteries, the shelves they sit on, and the whole works to a point where several hours after heating the cabin, they will still be cold bricks.

Just a counter balance to the other thoughts. You will come up with something.

 

[Wilecoyote]

They are fine being cold. Just can’t charge when cold. May shutoff at -20C however. So they might take a while to warm up when/if you arrive and they are that cold. If you don’t arrive in the dark at below -20, just use them until they are warm enough and turn your solar on after that.

I feel like out there they will never warm up enough to charge. Will they be alive after 6 weeks of -15 to - 20 ? I feel like if it’s - 16 for a week strait then a few days of -1 the batteries aren’t going to “ turn on “ and warm up quick.

 

[FishHog]

Mine warm up overnight inside my cottage. It takes awhile but get some warm air around them
As for being cold, they don’t care. If above-20c they will discharge for you use