Yamaha battery in VERY cold weather

I have a Yausa (not sure of the model) in my RX1 and I've started it cold at -50 without a problem.

It's the same battery that was in the sled when I bought it and that was a selling point. It hadn't been run in about four months and it was -36 when I showed up to look at it. The guy I bought it from was worried that it wouldn't start because it had been colder than -20 for about two months and it hadn't been run since he had changed the oil and installed the new battery in the early fall. He choked it and turned the key and it started in about 10 seconds and ran like a top. I figured that the engine was in good shape if it started and ran under those conditions. That was about 5000 miles ago.

Knock on wood, but I haven't had a problem starting that sled yet. Hopefully that trend will continue.

When people started having issues with the new lightweight lithium batteries in really cold temperatures some guys were hooking grip heater elements to the battery box and wiring them to a toggle switch. so they would draw a little current to warm the battery while they heating elements would slowly warm them up from the outside. you could rig something like that up and use it to draw a small current to keep the battery warm internally obviously if you left it on you could have problems just an idea

We've been running the Earth X lithium batteries for 3 years now. They are great. But at -35/-40C no battery really wants to go.
We tested the whole grip heater elements. It worked but it took a very long time to "activate" the battery. We had the grip heater wired in the max setting. It took on average 40 min of wait time to activate the battery to get the sled to start. On the test sled with out the grip heater it took less time about 15-20 min by just waiting and cranking the motor over.
What we ended up doing, is just wiring in the earth X "quick Connect" cables to the battery and routing the plug to a easily accessible spot, and just jumping it in the morning when needed. There Jump pack is small at easily starts the sled.
It takes minutes. In our opinion the grip heater elements work but are not worth the time, they just don't draw enough juice to activate the battery fast enough.