3 ms·

I think the solution for batteries in cold weather is to insulate the pack and heat the battery "coolant". Almost all modern EVs use liquid cooling of some kin

by elihu 4y ago

I think the solution for batteries in cold weather is to insulate the pack and heat the battery "coolant". Almost all modern EVs use liquid cooling of some kind. (Nissan Leaves are the exception; I don't know if they've added that in newer versions, but it's why Leaf battery packs were notorious for wearing out quickly.) I don't know if battery heaters are a common feature on current EVs. I'd think it would be particularly useful for LFP cells, which can be damaged if you try to charge them when they're below freezing. They can be discharged safely (if not efficiently) at much lower temperatures, which means you could "bootstrap" the car in cold weather by using the battery to heat itself until it gets warm enough to charge (without which you can't use regenerative braking). It wouldn't be that far-fetched to imagine a battery cell with a built-in heating element (e.g. an internal 1 ohm resistor across the battery terminals) that, when activated, keeps the cell at at least room temperature and shuts off when the battery gets up to temperature. Normally you'd only activate the heater when charging or driving.

osigurdson 4y ago
Resistive heating using a battery offends my sensibilities. It takes beautiful low entropy energy and irreversibly converts it high entropy heat.
- elihu 4y ago
  I can sympathize with that, but if the choice is between, say, using 1% of the battery capacity to heat the cell versus losing 25% of the capacity because they just don't work efficiently in the cold, going with the 1st option seems like the right move. Although maybe that's not right... if a large amount of energy is "lost" when the battery is too cold, that energy has to go somewhere. If it ends up as heat anyways, maybe it's really functionally equivalent to having a heating element in the cell. In which case the solution is probably just to insulate the batteries better.

by elihu 4y ago

osigurdson 4y ago

Resistive heating using a battery offends my sensibilities. It takes beautiful low entropy energy and irreversibly converts it high entropy heat.

elihu 4y ago
I can sympathize with that, but if the choice is between, say, using 1% of the battery capacity to heat the cell versus losing 25% of the capacity because they just don't work efficiently in the cold, going with the 1st option seems like the right move. Although maybe that's not right... if a large amount of energy is "lost" when the battery is too cold, that energy has to go somewhere. If it ends up as heat anyways, maybe it's really functionally equivalent to having a heating element in the cell. In which case the solution is probably just to insulate the batteries better.