Battery Preheat - Does it ever work?

[ElectricTundra]

I've been attempting to benefit from preheating the battery in my P85D to get regen back since it became available. Best result is to turn on cabin heat from the app while the car is plugged in to the wall charger while it's in our 36°f garage. With this I'll occasionally see the battery charge indicator eventually turn on in the climate screen of the app. I say eventually because it can sometimes take 5 or 10 minutes before it comes on. However, even after an hour it doesn't appear to ever actually give me any greater regen. And I say occasionally because it does not come on more often than it does.

Only twice (in dozens of attempts) have I seen the battery warming indicator come on when the car is not plugged in. There has been some debate if this should never happen or only when the battery has some certain SOC. Both times I had over 150 miles of range remaining (and was within 5 miles of home if they are perhaps looking at that to determine whether to do it or not). Once it was about +28°f and the other was about -3°f. Neither of these seemed to provide any regen though they were both less than about 20 minutes before I started driving and I've seen reference to preheat taking at least 40 minutes.

Have others had luck with this working? Any improvement in w/ 2018.4.1?

Thanks,

 

[Struja]

Mine turns on everytime from my phone, however, even after pre-heating for an hour, I see very little improvement in my regen (if any at all).

 

[navinsiri]

The battery heaters goal is to get you 30kW of regen. Once it reaches that point the heater will shut off. In case you didn't know full regen is around 60kW.

 

[ElectricTundra]

The battery heaters goal is to get you 30kW of regen. Once it reaches that point the heater will shut off. In case you didn't know full regen is around 60kW.

Thank you. Might be mostly a problem of expectations then. That's about what it normally has when I leave my garage without preheating so preheating may not even be applicable except when the battery is well below freezing.

I'd like to see a bit more regen from it but maybe there are good reasons for limiting the preheating. I get use to one pedal driving and having to switch back to the old way isn't much fun.

 

[navinsiri]

Thank you. Might be mostly a problem of expectations then. That's about what it normally has when I leave my garage without preheating so preheating may not even be applicable except when the battery is well below freezing.

I'd like to see a bit more regen from it but maybe there are good reasons for limiting the preheating. I get use to one pedal driving and having to switch back to the old way isn't much fun.

I guess they do it so the range doesn't decrease a lot while the car is just sitting there, but I'd like to have an option for it to fully heat the battery because I usually have more than enough range to get anywhere and would prefer to have full regen.

 

[SSedan]

I suspect the 30kw because once you have that much regen available driving/regen will warm the battery without wasting energy on the heater, and that warming beyond that would require a LOT of energy to make regen gain back a little......................................

 

[SeminoleFSU]

Your best bet is to time your charges to end just before you get ready to drive. Your battery will be warm and have a lot less regen limit if you do this. The other important thing is to keep range mode off... I think battery heats up quicker with it set to off, but eventually will allow the battery temp to rise higher than normal to get the highest voltage out of the pack. The problem is I believe it warms up to "no regen limit" slower with range mode enabled, even though it will eventually reach a higher pack temp over time.

Don't quote me on the range mode setting, this is just my observation on how it works - not anything I've read from a knowledgeable source.

 

[dave4444]

What outside temperature are you starting your preheat at? Battery heater will only kick on <30F or so, and you really don't need to preheat the battery unless it's <20F where regen will be non-existant.

One other trick when it's very cold to get the battery heater to kick on to start a charge (not because you want to preheat the cabin). If it's very cold (to the point where available regen would be 0) you can simply plugin and request charging. For the first 10-20 minutes the battery heater will draw wall power and zero power will go to charge the battery (because it cant). Once the battery is warm enough to charge the wall power will both run the battery heater and charge, then once battery heater is off, wall power will charge at full speed.

 

[jerry33]

Works for me, but the trick is to set the charge time to end about the time you start commute and preheat the cabin on HI before you start (range mode OFF or it won't work). At -10 to 0 C parked outside, start the charge 15 minutes before the time you'd start it in warmer weather. (Presumably even earlier for colder conditions but I don't have any first hand data for that.) With one cabin preheat cycle, the regen warning goes away between zero and ten minutes (range mode ON, cabin heat OFF when driving).

Morning cycle -10 to 0C:
02:15 start charge
04:20 charge ends (50-60 miles of range recovered)
04:30 cabin preheat starts
04:50 driving starts

14-50 @33 amps 90% SOC setting.

 

[dave4444]

One should keep in mind why you want to preheat the battery. The car will keep the battery within acceptable temperature range by itself to prevent damage without you doing anything, the only reason to preheat the battery is if you want max possible range once you get started. Otherwise you are just burning money (assuming you're paying the power bill), the cost of preheating the battery is generally more than you would lose by using your friction brakes (instead of regen) during the first 20-30 minutes of driving. Proper timing of charging is key to saving money, finishing a charge you would otherwise do just prior to driving is best as the battery heater (if needed) is serving a purpose (heating the battery so you can charge) and charging will heat it naturally as well.

 

[JohnSnowNW]

I use it quite a bit, usually I pre-heat for 30 min and I have more regen available than if I had not. After driving around for 15-20 minutes I often have full regen available.

 

[Scott_K]

However, even after an hour it doesn't appear to ever actually give me any greater regen.

There’s a big active thread where someone did the math on how long you have to preheat your cabin for before getting back to 100% regen. The numbers will vary based on the starting temperatures, but their math came out to something like 4-5 hours. Probably not something most people are willing to do on a daily basis. One other option people frequently discuss is scheduling your charge to complete shortly before your trip, then warming the cabin for 30 mins or so.

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