Battery Pre-Conditioning

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Fisher99

Well-known member
Joined
May 12, 2019
Messages
424
Would one of you knowledgeable people please educate me regarding battery pre-conditioning? I'm heading into my first winter with the i3 and now the temps are getting down into the mid 20's and low 30's at night, with a few nights already in the high teens. I know that conditioning takes energy out of the battery, so will reduce driving range, so I would like to pre-condition the batteries while the i3 is still connected to my L2 charger at home. I had originally thought that the "climatize" feature would also pre-condition the batteries but I recently saw a post in another thread that seemed to indicate that it doesn't.

So, some questions: Does climatizing pre-condition the batteries? If not, is there a way to pre-condition the batteries while still attached to my L2 charger? And if I can indeed pre-condition the batteries, how long should I expect that to take when the temps are in, say, the mid 20's to low 30's?

Thanks.
 
To precondition the HV battery pack, set scheduled departure times in your menu. The car will start the preconditioning 150 - 190 minutes or so before the departure time you set - actual time I think depending on temperature, etc the computer determines it needs to complete the preconditioning (while plugged in) . Climatize just warms up or cools the cabin and takes 30-40 minutes.
 
Bummer. That doesn't really work for me since I'm a retired guy and don't have a set schedule for when (or even if) I might want to leave the house in the morning.

However, as I am pondering this, I wonder if there would be any merit in setting, say, an 8:00 AM departure schedule, to pre-condition the batteries even if I might not be going anywhere until later in the morning. Of course if it is still in the 20's or 30's, I wonder how long the pre-conditioning would be good for before it would need to be done again...
 
how long the pre-conditioning would be good for before it would need to be done again

Preconditioning would last however long it takes the battery pack to cool down in whatever the current ambient temperature is. Basically preconditioning is just warming the battery pack up (or cooling it) to best operating temperature. Optimum temperature for the battery pack is 25 to 40 degrees Celsius, or 77 to 104 degrees Fahrenheit. The further off the optimum temperature the battery pack is, the more the range is affected.

Be aware that preconditioning won't start at all, unless there is at least three hours available before the set departure time, and the car is plugged in. If the car is not plugged in, only cabin climatization occurs.
 
Interesting. I think I might set a 10:00 AM departure, since I rarely drive anywhere before then. And on days that I do head out a bit earlier, at least the battery would be partly pre-conditioned. Wish I had room to keep the i3 in the garage, but don't want to move out either of the other 2 vehicles.

This is good info. Thanks!
 
Fisher99 said:
Interesting. I think I might set a 10:00 AM departure, since I rarely drive anywhere before then. And on days that I do head out a bit earlier, at least the battery would be partly pre-conditioned. Wish I had room to keep the i3 in the garage, but don't want to move out either of the other 2 vehicles.

This is good info. Thanks!

Just something I came across through trial and error, because I too have an undefined departure schedule, daily.

So I generally leave the pack to charge to about 90% full, and then EVSE cuts off. But before departure I go in via the app and start charging again. Typically I'll do this about 30-40 minutes prior to departure, and I've noticed pretty much the same range doing it this way, rather than setting a preconditioning timer. It also saves electricity, because you're using electricity to both fill the pack, and warm it (charging batteries warms them up significantly). For more data points, I've noticed the car still pulls 6+kW until about 94-95% then tapers down to 2.5-4kW until 100% full. When I used to do the precon, i believe it pulled about 2kW from the mains to heat the battery. I'd rather put that 2kW into the pack and heat it at the same time. Give it a try.
 
If you're also conditioning the cabin, I've seen mine drawing about 20A. The battery electric heater is a 1Kw device. Depending on how hot or cold it is, conditioning the cabin can take a fair amount, but it only runs for about 20-30 minutes just prior to your programmed departure time.

While plugged in, if you just tell the i3 to condition the cabin, it may or may not activate the charging. There's some hysteresis, so the level has to drop a bit before it kicks in. FWIW, it will not warm the batteries unless it's plugged in.
 
Interesting approach, but unfortunately my EVSE doesn't have the ability to stop charging at a set percentage, and does not have app control. But, I could use the BMW app to track charge percentage and manually disconnect the EVSE. Then plug it back in again in the morning an hour before leaving. Might give this approach a try, although it's likely that I'll get tired of the hassle pretty quickly. Maybe somewhere down the road I'll cough up the $$$ for a smart EVSE.
 
If you have a home automation system, you should be able to find a 240vac power switch for your EVSE. Note, many, but not all EVSEs, will restart properly after a power outage. Some won't if the vehicle is still attached.
 
A switch is an interesting idea but would only help with turning the charger off/on. I'd still have to manually track the charging percentage if I wanted it to stop at, say 85%. Even though my i3 sits outside, the charger is plugged into an outlet inside my garage, so it's fairly easy for me to unplug it and re-plug it without having to go out into the cold. I did this last night. Unplugged it at 85% and now this morning just plugged it back in. Charging started up as per normal.
 
Since charging the batteries does warm them, delaying the final charge until just prior to your intended departure time could save some Kw, but I don't really think it will affect your overall battery health. You could get a good approximation of when to turn the charging off/on by noting the time on the display until full charge when you first plug in...take that and shut it off prior to being full, then restart long enough prior to when you want to leave with a full charge.

But, unless it's really cold out, the savings may not be all that much. It's certainly more convenient to just plug it in when you get home and unplug it when you get ready to go.
 
Yeah, I'm currently weighing the benefits of a bit more battery life (per drive) vs the pain of manually monitoring and managing the charging process. I did the manual process yesterday and it did appear that the battery percentage declined at a lower rate with the pre-conditioned batteries than just starting out with a full charge but no pre-conditioning. Not scientific, and maybe wishful thinking, but it did appear to have a slower initial drop rate.

I'm really a bit bummed by how much the lower temps have shortened my pure electric driving range. I'm estimating about 25% shorter range and we still have colder temps to come. Of course we are running the heater at 72-74 degrees and using the heated seats for the first few minutes to "unfreeze" the seats. I understand that it is more energy efficient to use the seats and not the heater, but my wife isn't willing to sacrifice her comfort for a few more miles of range. Plus, in this weather I need warm air blowing over the windshield to keep it defogged.

I do at least "climatize" the car while it is plugged in before we leave the house, so it is warm and toasty before we get in, so that takes the initial "cabin up to temp" load off of the batteries. But much of our driving consists of shopping, banking, etc., which means multiple stops with the cabin cooling down and needing to be reheated multiple times. Oh well, I guess this is just how it is. But I think I will probably be getting some use out of the REX this winter...
 
Using 7:45 AM scheduled departure, this is what my EVSE records:
pre_condition_030.jpg

  • ~4:50 AM - a short, low level charge event.
  • ~7:15 AM - another short, low level charge event.
  • ~7:30 AM - the main cabin warm-up begins
  • ~8:05 AM - the main warm-up ends
My recommendation is schedule the warm-up about 20 minutes before your regular departure. Charging should end just as you're ready to leave.

Bob Wilson
 
So I have read these posts over and over looking for an answer for the question: If our 2015 REX is sitting for a few days in this now colder weather here in Western Massachusetts is there a way (if necessary) to occasionally warm the HV battery, My friend has a 2019 Chevy Bolt and his car is pretty much required to do heating (or cooling in warmer weather). I obviously can do the battery conditioning and interior climate conditioning before use but was wondering if the HV battery should be warmed. A couple of months ago I had the car in for service and the service advisor told me the car would automatically condition as required if plugged in, I haver not seen any sign of this. I have an Eyedro house monitoring system and no short spurts of draw are evident. I have a Juice Box 40 wall mount charging station. Any suggestions would be appreciated, thanks!!
 
BMW does say the batteries can be damaged if they are nearly discharged and allowed to cold soak at really low temperatures (not sure they actually give that a number). But, not sure they'd be damaged if they were charged and then got really cold. They definitely will discharge more slowly and less completely if they are cold soaked. Heat lets everything move better, even electrons. If plugged in, the car will take care of itself.
 
jadnashuanh said:
BMW does say the batteries can be damaged if they are nearly discharged and allowed to cold soak at really low temperatures (not sure they actually give that a number). But, not sure they'd be damaged if they were charged and then got really cold. They definitely will discharge more slowly and less completely if they are cold soaked. Heat lets everything move better, even electrons. If plugged in, the car will take care of itself.

I guess that's the real question (the part I bolded and italicized). If the car is sitting outside in below freezing temps for weeks at a time, is not driven, but is plugged in, will the battery take care of itself? I'm sure that it will keep the battery charged, but aside from topping off the battery when required, will the car also manage the battery temperature? Or if the battery is charged, maybe ambient temperature isn't an issue? Given that my i3 has the 20" wheels and summer tires, it will be spending much of the winter just sitting outside, plugged in, and not driven, in temps that can range from low teens to low 30's. I'm assuming that the car will take care of the battery, but I hate making assumptions...
 
It's my understanding that damage as a result of cold, is only an issue when the batteries are nearly discharged. So, it does not, to my knowledge, warm them when they are higher than some set value. If too hot, it will try to cool them. It can take quite a number of days with the car just sitting before the battery level drops enough for the car to turn charging back on, so it's not like it's constantly sitting with power applied. The car makes the determination when it needs power.
 
I was an earlier poster and have another charging pre-conditioning question. I have the setting of Departure Time under control and I set this in the car when the EVSE is plugged in. Thusly the car starts charging immediately because the "Start Charging Immediately" is checked. I cannot uncheck this, possibly if I got into setting the charging to begin at a time when electricity is the cheapest but here in Western Massachusetts thru Eversource it is the same rate all of the time. Sometimes the reason I don't want to charge to 100% is because I like to run the REX every 2-3 weeks to make sure it will start if necessary. The question is how can I pre-condtion without charging to 100% and can I. Another question: is preconditioning part of a free service on the Connected Ap or is it part of the subscription services. When I go into that site it says for the three ( I think) packages I am paid up until like 2024 or something like that for our 2015 i3 but it doesn't appear to work. Thanks in advance for your responses.
 
Temps here have been in the 20's, but since I have no set schedule I have not been able to use the scheduling option to pre-condition the battery. Until now. This morning I knew that I had to leave the house at 9:00 AM so last night I scheduled a departure time and pre-conditioning. All I can says is WOW!!! What a difference that made in battery consumption! Well worthwhile if you have a set schedule.

Makes me wonder if I shouldn't set it to pre-condition for, say, a 10:00 AM departure each day. Even though I don't have a set schedule, I rarely leave before 10 on days that I do use the car. Of course that begs the question of how long it takes with temps in the high 20's for the pack to cook back down again and make the pre-conditioning a wasted of electricity. 30 minutes? An hour?
 
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