Battery warming drain

[GA_Rivian]

Sorry if this is an old and settled topic, but are there any numbers on battery drain related to keeping the battery warm? Ideally, something like KwH / deg below 0C/32F or something like that. Also any numbers related to AC power required under the same circumstances when plugged in?

It's -22F outside right now. If I have a breakdown somewhere, or I'm parked at a ski cabin or fishing lake, how long would it take for the battery to be permanently damaged?

Also, has anyone experimented with a skirt of some kind to extend the time? I'm thinking of making a skirt of wool blankets and wondering how much it would help. I have some simple cloth drapes in front of big (5'w x 7'h) triple-pane windows in my sunroom and they make a big difference.

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[R.I.P.]

Sorry if this is an old and settled topic, but are there any numbers on battery drain related to keeping the battery warm? Ideally, something like KwH / deg below 0C/32F or something like that. Also any numbers related to AC power required under the same circumstances when plugged in?

It's -22F outside right now. If I have a breakdown somewhere, or I'm parked at a ski cabin or fishing lake, how long would it take for the battery to be permanently damaged?

Also, has anyone experimented with a skirt of some kind to extend the time? I'm thinking of making a skirt of wool blankets and wondering how much it would help. I have some simple cloth drapes in front of big (5'w x 7'h) triple-pane windows in my sunroom and they make a big difference.

Being able to leave the vehicle plugged in, even if it's just to 110 will certainly help.

 

[KootenayEV]

My Leaf wouldn't turn on the battery heater until -20C (-4F); not sure what Rivian has programmed. My battery was at -8C this morning after cold-soaking at -10 to -20C for over 24 hours. Truck warmed it up to 0C and stopped conditioning after about 20 mins of driving.

Would need someone who has their truck parked at cold temps to either really watch their drain over >24hrs and compare to previous drain at warmer temps, or someone with a scanner. In theory you could math it out, but there's a fair amount of assumptions you would need to make so I think the answer would be a pretty wide range. Personally I'm not worried about parking it at the temps you reference for a few days, provided it is around 50% or so when I park it.

 

[GA_Rivian]

My Leaf wouldn't turn on the battery heater until -20C (-4F); .... My battery was at -8C this morning after cold-soaking at -10 to -20C for over 24 hours

Interesting. I thought it wasn't supposed to be good for the batteries to go below 0C, and that they would heat to keep at least that. If that's not true, that is encouraging.

Would need someone who has their truck parked at cold temps to either really watch their drain over >24hrs and compare to previous drain at warmer temps,

That may be me in a month or so. We get -20F to -40+ usually once a year, and don't have a heated garage. I have a watt-hour meter for a 110 circuit. I'm thinking if I bring the truck up to 80% and then plug that in I will have a pretty good idea, assuming ~1.5KW is enough to keep it heated at those temps.

 

[JayinNJ]

Interesting. I thought it wasn't supposed to be good for the batteries to go below 0C, and that they would heat to keep at least that. If that's not true, that is encouraging.


That may be me in a month or so. We get -20F to -40+ usually once a year, and don't have a heated garage. I have a watt-hour meter for a 110 circuit. I'm thinking if I bring the truck up to 80% and then plug that in I will have a pretty good idea, assuming ~1.5KW is enough to keep it heated at those temps.

It won't cause permanent damage at low temperatures. You just don't get optimal performance.

 

[R.I.P.]

It won't cause permanent damage at low temperatures. You just don't get optimal performance.

No sir, that is very wrong. Both charging and discharging of lithium batteries outside of proper operating ranges can, and absolutely will permanently damage the battery.

https://www.renogy.com/blog/battery...how cold is too,any useful energy is produced.

Just one source from a lithium manufacturer quoted here, but anybody who's worked with lithium batteries is aware of this. This is why it is so important for the BMS to keep the batteries in a healthy range, or to warm them up properly before use/charging.

 

[KootenayEV]

Interesting. I thought it wasn't supposed to be good for the batteries to go below 0C, and that they would heat to keep at least that. If that's not true, that is encouraging.


That may be me in a month or so. We get -20F to -40+ usually once a year, and don't have a heated garage. I have a watt-hour meter for a 110 circuit. I'm thinking if I bring the truck up to 80% and then plug that in I will have a pretty good idea, assuming ~1.5KW is enough to keep it heated at those temps.

If they are not in use, they can sit almost indefinitely below freezing, provided it doesn't get so cold that the electrolyte freezes.

As RIP points out, once you start using the battery it is different. My understanding (from a decent amount of reading on the topic, including deep dives into Jeff Dahn presentations, but I am NOT an expert) is that the battery cannot tolerate as high of a 'C' level as it gets colder. Note that what we usually speak of for "freezing" (ie 0 celcius, 32F) is an arbitrary point as far as a battery is concerned; freezing for a battery means the electrolyte freezes.

Like all chemical reactions, the rate at which it can occur is heavily influenced by temperature. When it is colder, the battery can discharge at a higher 'C' than it can charge. This morning my truck showed -8C for the battery:

• The power available was roughly half of normal
• Effectively zero regeneration was available

The truck conditioned the battery, and ten minutes later I had about 3/4 of my power available and 1/2 my regeneration, with the battery still below "freezing".

This condition also isn't static for a given temperature: a small amount of ions can shuttle back and forth from the cathode/anode relatively quickly, but when you start having continuous recharge, you run into regeneration limits quickly at these temperatures.

As an aside, the type of degradation and where it occurs (e.g. cathode/anode) is different at either end of the temperature spectrum for the battery. Look up plating and dendrites if you are really interested. (Quantumscape is working hard to control dendrites, because they grow in this 'spiky' manner and they don't want them to puncture the ceramic separator they have developed as part of their solid state batteries - punctured separator = dead battery!)

edit: clarity

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