Battery Warming Woes ....

[cirrussk]

Hi there,

I've only had my car for a couple months, so just getting used to it ...

2016 Tesla S75 running software 2017.50.2
iPhone X - iOS 11.2.1
Tesla App - 3.3.0

Two questions in regards to battery warming:

Living here in Phoenix, Arizona. Car is parked outside. Average low temp's 35 degrees when I start driving in the morning. The car charges overnight with the Tesla wall charger, though finishes around 10pm. I start driving around 6am.

As I've mentioned in other posts, I've tried everything to warm the battery before I leave home. Finalized charging of the car at the time of departure and have tried the new software with the battery heater.

(1) The little car battery warming icon has stopped appearing on my App. I must have been one of the first one's to get the new Tesla car software + iPhone App, and I did see that little icon starting to come up. However I haven't seen it in a few weeks. Anybody know of any changes to that procedure? I was just turning on Climate Control and the battery heater icon flipped on automatically.

(2) Yesterday I took it on a mini trip. Car battery was cold upon departure and I drove 100 miles to a Supercharger. Of course the battery warmed up after about 20 min into the 110 min drive. Parked the Tesla at the Supercharger. Ambient temp was about 70-75 degrees. Charged it to 100%, which took about 1 hour or so. I came back to the car after about 2 hours and started driving again, though the battery was cold soaked again. Is that normal ??? Lately every time I get into the car, the battery is cold soaked.

-Sam

 

[MorrisonHiker]

Instead of charging the car in the evening and having it finish around 10 pm, it would be better to schedule charging so that it ends right about the time you would use the car in the morning.

 

[David29]

Hi there,

I've only had my car for a couple months, so just getting used to it ...

2016 Tesla S75 running software 2017.50.2
iPhone X - iOS 11.2.1
Tesla App - 3.3.0

Two questions in regards to battery warming:

Living here in Phoenix, Arizona. Car is parked outside. Average low temp's 35 degrees when I start driving in the morning. The car charges overnight with the Tesla wall charger, though finishes around 10pm. I start driving around 6am.

As I've mentioned in other posts, I've tried everything to warm the battery before I leave home. Finalized charging of the car at the time of departure and have tried the new software with the battery heater.

(1) The little car battery warming icon has stopped appearing on my App. I must have been one of the first one's to get the new Tesla car software + iPhone App, and I did see that little icon starting to come up. However I haven't seen it in a few weeks. Anybody know of any changes to that procedure? I was just turning on Climate Control and the battery heater icon flipped on automatically.

(2) Yesterday I took it on a mini trip. Car battery was cold upon departure and I drove 100 miles to a Supercharger. Of course the battery warmed up after about 20 min into the 110 min drive. Parked the Tesla at the Supercharger. Ambient temp was about 70-75 degrees. Charged it to 100%, which took about 1 hour or so. I came back to the car after about 2 hours and started driving again, though the battery was cold soaked again. Is that normal ??? Lately every time I get into the car, the battery is cold soaked.

-Sam

When you say it was "cold soaked," do you mean that there was a restriction on regenerative braking? If so, that is because you charged to 100%. The battery would not be cold if the ambient temp was 70F and you charged to 100%.

The battery cannot accept any more charge when it is at 100%, so you get a restriction on regenerative braking until you use enough charge to allow the battery to accept some more charge.

If you do not really need 100%, don't charge that high. (Plus, it is inefficient to charge that high -- it takes a long time. It is more efficient from a time standpoint to charge only enough to reach the next place where you can charge.) Maybe charge only to 90 or 95%, and that leaves some margin for regenerative braking.

As for that battery warming indicator, it is possible the you will not see it if the low temperature is in the mid-30s. I think it only comes on if the battery is colder than that. I saw one or two threads where someone said the battery only warms itself at 28F or colder. (I cannot personally say what the specific temperature is when the battery heater comes on.)

 

[Brass Guy]

Charged it to 100%, which took about 1 hour or so. I came back to the car after about 2 hours and started driving again, though the battery was cold soaked again. Is that normal ??? Lately every time I get into the car, the battery is cold soaked.

Very unlikely that the battery was "cold soaked" given the conditions reported; but since you charged to 100% you would not have regenerative braking available.

Also it has been noted widely in this forum that the battery heater will only heat enough that you have about half (30kW out of 60) regenerative braking available.
If the charge session is long enough and finishes shortly before you depart in the morning, you may have full regen.

Edit: @David29 beat me to it - did it really take me 9 minutes to type that?

 

[AWDtsla]

(1) The little car battery warming icon has stopped appearing on my App. I must have been one of the first one's to get the new Tesla car software + iPhone App, and I did see that little icon starting to come up. However I haven't seen it in a few weeks. Anybody know of any changes to that procedure? I was just turning on Climate Control and the battery heater icon flipped on automatically.

Warming "feature" is a dud. You will not get a "fully" warm battery from it. Sorry you were mislead.

 

[strider]

I guess I fail to see the problem here. Why do you care if the battery is cold? The process of discharging via driving will warm it up naturally. Why would you burn electrons (which for most people are from fossil fuels - certainly if you're using an SC) to do something that will happen in due course of use? It's not like an ICE where you can't get cabin heat until the engine is warm. So you have to use the brake pedal a little more for a few minutes? I don't get it.

Also, as others stated, if you charge to 100% you will lose regen until there is enough space in the battery for additional charge.

 

[TexasEV]

You live in Phoenix and are concerned about a cold battery? Chill out (or should I say warm up) and just enjoy your car. And stop leaving your car parked at a supercharger for 2 hours.

 

[Don TLR]

If you're only driving 110 miles to a supercharger why charge to 100% before leaving?

 

[clostridium]

I guess I fail to see the problem here. Why do you care if the battery is cold? The process of discharging via driving will warm it up naturally. Why would you burn electrons (which for most people are from fossil fuels - certainly if you're using an SC) to do something that will happen in due course of use? It's not like an ICE where you can't get cabin heat until the engine is warm. So you have to use the brake pedal a little more for a few minutes? I don't get it.

Also, as others stated, if you charge to 100% you will lose regen until there is enough space in the battery for additional charge.

It comes down to whether you spend the energy before the drive or during the drive to achieve the various goals like heating the cabin (not as important) and heating the battery.

The battery heater in the car uses a lot of energy and if you've got a longer drive ahead of you it can significantly impact range and to a lesser extent not having regen impacts range because you aren't reclaiming energy from braking. Putting it in range mode theoretically stops (or greatly reduces? this is not entirely clear to me) the battery heater and leaves it to just passive heating in the manner you mention but it takes a pretty long time to heat the battery up a reasonable amount in this passive manner.

The energy spent on heating the battery ahead of time is mostly not wasted if you are headed out on a longer drive since your options for that drive would be to either burn energy on the battery heater while driving or wait a really really long time for the battery to passively heat. You are just shifting when the electrons are burned. The question that we'd need more data to figure out is how much the lost regen during the longer time it takes to heat the battery passively costs in terms of energy. If it doesn't cost much then heating the battery ahead of time is mostly for the convenience of having regen and you should just be in range mode all the time.

 

[TexasEV]

You’re overthinking this. Just drive the car. Especially in Phoenix where heating the battery would be the least of anyone’s concerns.

 

[strider]

It comes down to whether you spend the energy before the drive or during the drive to achieve the various goals like heating the cabin (not as important) and heating the battery.

The battery heater in the car uses a lot of energy and if you've got a longer drive ahead of you it can significantly impact range and to a lesser extent not having regen impacts range because you aren't reclaiming energy from braking. Putting it in range mode theoretically stops (or greatly reduces? this is not entirely clear to me) the battery heater and leaves it to just passive heating in the manner you mention but it takes a pretty long time to heat the battery up a reasonable amount in this passive manner.

The energy spent on heating the battery ahead of time is mostly not wasted if you are headed out on a longer drive since your options for that drive would be to either burn energy on the battery heater while driving or wait a really really long time for the battery to passively heat. You are just shifting when the electrons are burned. The question that we'd need more data to figure out is how much the lost regen during the longer time it takes to heat the battery passively costs in terms of energy. If it doesn't cost much then heating the battery ahead of time is mostly for the convenience of having regen and you should just be in range mode all the time.

Thank you for the insight. I completely agree that if it's cold enough for the car to engage active battery heating it will trash your range and in that case I totally get using it while plugged in to not lose range.

My post was from the standpoint of the OP being in Phoenix and so I don't believe it would get cold enough there for the car to engage active battery heating while driving.

As for lost regen, I'm afraid there would be too many variables to come up with good guidance. If you're headed out onto an uncongested freeway drive then you're not using much regen so you shouldn't heat (and you're going fast so the battery will passively warm more quickly) but if you're going out into stop and go you could use a lot of regen... then the question is whether regen or heating is more efficient... Interesting exercise...

 

[AWDtsla]

but if you're going out into stop and go you could use a lot of regen... then the question is whether regen or heating is more efficient... Interesting exercise...

You'd have to have large drop in altitude from where you are warming for it to matter. Stop-n-go nets almost nothing. Even stopping from highway speeds is almost nothing, very simple math to approximate:

50kW for 10 seconds = ~140Wh (assume approx. highway stop)
5kW for 30 minutes = 2500Wh

So you would need to go from 75mph to ~0 mph 18 times to make up for that preheat session.

 

[strider]

Thanks for the note. My gut was telling me that from a energy loss standpoint not having regen while the battery was cold was negligible but didn't want to put forth an opinion as fact.

So that leaves the only reason for pre-heating is if you need maximum range for that drive.