[Dormant] Electric Vehicles

Cold doesn't damage the battery. Batteries are basically electricity pumps. When they're cold they're less willing to give up their electrons. But being cold isn't inherently good or bad. It essentially reduces the efficiency of the pump.

Generally speaking the thing you want to avoid with ev batteries is getting them too hot. Heat damages them more than anything else.

The next temperature related thing is putting a heavy load on the battery when it's too cold. The important thing with this is a cold battery itself isn't necessarily bad, it's putting a heavy load on a cold battery that's bad

Also generally speaking, the healthiest state to store a battery is half charged.

If you'd like to read up on it the thing to search for is "lithium plating."

So long story short, if you're going to leave your EV for weeks at a time, the best thing you could do is leave it plugged in to a wall outlet and set the charge limit to 50%. Remember, EV batteries don't lose electricity when they're cold, they just can't pump all the electrons in them because they're cold. If you leave it plugged in and set the charger limit to 50% it'll maintain the battery at a good state of charge. It won't draw that much electricity either.

I'm not an EV owner (but spent 50 years in a climate like that). I found this: https://cluballiance.aaa.com/the-extra-mile/articles/prepare/car/store-an-electric-vehicle-over-the-winter

and this: https://insideevs.com/features/342917/cold-weather-electric-car-tips-maximize-your-ev-for-winter/

for example, by searching for "storing an EV in a cold climate".

Like a gas or diesel, it's important to keep your battery fully charged for those arctic mornings (EVs have two!) Even then they need help (I used to plug-in an engine 'tank heater' an hour early on those days.)

(As an ex-diesel mech, at those temps, the fuel gets thick! So do the electrolytes in batteries, so they take longer to charge.) So for an EV, look into 'preconditioning' the battery before re-charging. )

Most EVs have something Iike a heat pump to keep battery temperature optimized and extend the life of the battery pack. Most EV user manuals tell you to keep the car plugged when not in use during extremely cold or hot weather. This way the batteries can be heated or cooled without draining car power. If you don’t do this, the temperature regulating system will kick in on battery power, and start to drain the batteries until there’s nothing left.

This heat-pump article in Wired today (Jan 19) may be of some use to someone.

"How the Mighty Heat Pump Is Helping (but Not Solving) EVs’ Cold Weather Problem"

https://www.wired.com/story/heat-pump-helping-but-not-solving-ev-cold-weather-problem/

I don’t know about starting difficulties, because I was in a warmer climate, but there are other complications for the cold.

I used to have a 2018 Nissan Leaf (I bought it used, but the battery was still testing at 100%), which ostensibly had about ~240km range. It didn’t get to -30C, but at about-5C if you use zero climate control (also different from an ICE car, it stays colder because the engine isn’t hot), you could get about 210 km. With low climate control, it’s more like 160 km (I don’t think I ever used high heat, but I imagine that’s more difficult in -30). Depending on your lifestyle, that’s not a big deal, but I had to charge in inconvenient places anytime I wanted to do more than a commute to work or local errands in the winter.

Today’s EVs are generally higher range, so factor that in as well. If it’s possible to do an extended test drive, I’d suggest trying one in winter.

We should be specific. This would be the standard 12v battery at fault; the pack batteries aren’t used to start an EV, not from what I’ve ever seen. I’ve a VW ID.3 and we had our 12v battery replaced with a heavy-duty one under warranty because many modern cars and their telemetrics, subsystems, cabin heating, etc will drain the 12v starter battery over an extended period of just sitting. The 12v usually runs the cockpit - not your big battery. Your big battery will top the 12v off.

The pack battery can sit for weeks - you do need to make sure it’s about 50-60% charged, no more or less, or you can incure aging to the battery. I’ve spent 3 weeks away a few times and lost 3-5%, so roughly 1%-1.5% a week, and this is both in Dutch winter (-2C) and summer (20C). It’s also important to not have the car preheat needlessly, so if there’s a scheduled departure time in the system, turn them off for that period you’re away. THAT runs off the 12v battery and will drain both batteries quickly.

But this is also the same as it’s ever been for ICE cars too - I lived for a decade in Colorado and we’d have glow-plug and charger boxes near the parking so we could trickle-charge a battery or keep the engine oil from becoming sludge when starting.

It depends on a lot of factors including the battery chemistry.

NMC (Lithium ion) batteries are common in high performance cars and older EVs. They should be kept between 20% and 80% charge for normal use. 60% is ideal for storage, but anywhere in that range will do.

LFP (Lithium ion) batteries are common in cheaper and newer EVs. They don't have a problem with being stored at 100%, and do have issues with not being regularly charged to 100% (monitoring gets less accurate over time until fully charged again), so leaving it at 100% is fine.

Lead acid (particularly calcium) batteries get damaged when discharged too much, so it's fairly important to keep them topped up. If you are leaving the car for a long time, it could be worthwhile to connect a trickle charger to the 12V battery to prevent the car's computer from gradually draining the battery. Some cars will top up the 12V battery from the high voltage battery if left for a while, so this may not be needed.

While I have little experience with low temperatures, I suspect that the car will be fine if left as stated above. The battery shouldn't get damaged by low temperature storage, and shouldn't lose much charge over time. Just don't expect full performance immediately after returning to it.