Pre-conditioning, regen, and cold weather

[chracatoa]

So, I have a question. If we warm-up our car before leaving in the morning, do we still have regen?

My hypothesis is no. Warming up the car will help, but regen will still be reduced even after the car/battery is/are warm.

Here's my reasoning:

I noticed something interesting yesterday. My commute to work which is usually efficient (since I go mostly downhill) spent 329 wh/mile. That was a surprise because my garage was warm-ish yesterday (17C/62.6F).

I know that cold weather can cause that, but I thought that by having the car warmed up, it should be fine. But, apparently, I was wrong. Yesterday it was 4C (39.2F). The garage was at 17C (62.6F).

Today, I decided to pay more attention to it. The temperature outside was 5C (41F). Inside the garage, the temperature was 18C (64.4F). Fifteen minutes before I left, I warmed up the car to 22C (71.6).

So, the car spent the night in the garage and the temperature was never below 18C (64.4F). I warmed it up to 22C (71.6F). And yet, the moment I stepped inside the car, I already saw the dots below the gears, indicating regen was limited (my battery was at 83%). How? Why? Are the dots are based on the external temperature given over LTE?

Anyway, today I got 301Wh/mile, still way above what I usually get, even though the car was warm before I left.

 

[Kermee]

I've done a fair bit of testing on this recently.

Schedule your overnight charging (least 3 hours of charging) to coincide with your target SoC charge when you're about to leave the garage. That'll help reduce to completely eliminate the no-regen dots since charging helps keep the battery pack warm.

Climate controls have no affect on battery heating via motor unless the symbol appears on the battery status.

 

[chracatoa]

Yes, but that means 18C (64.4F) is considered "cold" for the battery, right?

 

[TLej]

Battery temp isn't connected to cabin temp (which is what you're setting when you set the car to warm up) other than it will use some power to heat the cabin, and using power puts heat into the battery. It takes quite a bit of pre-heating (or charging at a high-ish rate) in order to get heat into the battery. Days where it's 4C outside, the regen limit only goes away on my S if I've been driving for more than about 1/2 hr.

I don't know how different the 3 is in terms of how quickly it heats the battery and what the power penalty is for doing so, I'm quite curious to see it it warms up faster and/or uses less power to do so than what my S does.

 

[RangerRick]

I was in the mountains recently camping and headed out in the morning to leave. Temperature had dipped into the 40s overnight but was 60-something by the time I was driving but I still had reduced regen.

 

[Nosken]

Don’t forget, if roads are very slippery, limit Regen by setting it to low to eliminate the “braking” effect causing tires to slide. I have a “Snow” driver profile.

 

[dsvick]

Warming up the temperature inside the cabin does not always warm the battery sufficiently. I do know that if the temperature is close to or below freezing the car should also turn on the battery heater when you turn on the climate control. The other way, as @Kermee mentioned is to time your charging to finish close to when you expect to leave.

 

[chracatoa]

I guess I'm talking about "cold" vs "really cold."

The garage is at ~65F at its coldest. The dots still show up. Therefore, 65F is cold for the battery. I thought that only temperatures below 50 would cause the dots to show, and regen to decrease.

Of course, outside is 39F, but the car hasn't left the garage yet.

 

[DrDabbles]

There's a couple things to consider here. The temperature "now" isn't of real importance generally speaking. The battery pack has mass, and that mass needs to be cold soaked for the pack to be considered cold. So if the overnight temperatures were 40F for hours and hours, and it has just warmed up to 60F for an hour or so, the pack is only just starting to warm up to ambient temperature. Compare it to frozen meat left on the counter top to thaw. An hour after it's out of the freezer the meat is still frozen, but if you wait 6 hours it's much more warmed through.

Anyway, the HVAC system does not consume enough energy to warm the pack in a meaningful way. Tesla Bjørn has done a couple videos about this with several different EVs. Driving and regenerative braking warms the pack much faster than nearly anything else, but having your car plugged into your charger and pre-heating the cabin will cause the car to begin to gently warm the pack a bit. There's a special icon that shows up on the mobile app to indicate that warming is happening. But again, the amount of energy put into the pack for heating is negligible compared to what is produced by driving.

 

[chracatoa]

Nope, the garage is insulated, and the coldest temperature is just when we're about to leave in the morning - i.e. 65F. I know this because the thermometer I have in the garage is one of those that tells me the extreme temperatures of the night (coldest/hottest).

 

[ewoodrick]

The best way to look at it is with the bar graph under the speed. Are you seeing it go to the left? That's regen.If you've got dots on the line, then that's regen limiting.
I really doubt if batteries are limited at 60 F.

 

[Kermee]

Nope, the garage is insulated, and the coldest temperature is just when we're about to leave in the morning - i.e. 65F. I know this because the thermometer I have in the garage is one of those that tells me the extreme temperatures of the night (coldest/hottest).

Charge up to 70% or 75% overnight instead of over 80% and see if you still have the dots. I remember I still had 3-4 dots at about 84% SoC. That's the only other thing I can think of if ambient doesn't drop below 65F.

 

[astrowunder]

Charge up to 70% or 75% overnight instead of over 80% and see if you still have the dots. I remember I still had 3-4 dots at about 84% SoC. That's the only other thing I can think of if ambient doesn't drop below 65F.

Yes, the 1st time I charged to 100% is when I noticed huge reduction in regen- it was almost nonexistent until I put enough miles on the trip to leave room back in the battery. Be warned that the driving style changes drastically when that happens- no significant regen braking.

 

[Tezlanian]

Warming up the temperature inside the cabin does not always warm the battery sufficiently. I do know that if the temperature is close to or below freezing the car should also turn on the battery heater when you turn on the climate control. The other way, as @Kermee mentioned is to time your charging to finish close to when you expect to leave.

There's no battery heater on the 3, only cooling. Heating is done passively by power draw. As stated by others you'll only get good preconditioning by charging on a schedule. If you are plugged in and just heat the cabin that's being drawn from your grid, not the battery. If you're not plugged in preheating the cabin can help a bit. I preheated the cabin for about 5 minutes unplugged when it was roughly 40F(~4.5C) and I had full regen. Had the heat set to "HI". The vehicle had only been sitting for about 3 hours though so the battery may have not fully cooled. Can't wait until it gets really cold to test stuff out.

 

[chracatoa]

Yes, the 1st time I charged to 100% is when I noticed huge reduction in regen- it was almost nonexistent until I put enough miles on the trip to leave room back in the battery. Be warned that the driving style changes drastically when that happens- no significant regen braking.

They should still enable a non-functioning regen so we don't feel the difference.

 

[Tezlanian]

They should still enable a non-functioning regen so we don't feel the difference.

The energy has to go somewhere though.

 

[Cyberax]

There's no battery heater on the 3, only cooling. Heating is done passively by power draw.

Not quite. They use the drive motors for heating, it can be intentionally run in such a mode that it produces a lot of waste heat that can be fed back to the battery.

 

[Tezlanian]

Not quite. They use the drive motors for heating, it can be intentionally run in such a mode that it produces a lot of waste heat that can be fed back to the battery.

Yeah I heard about that before the 3 came out but haven't found any real information on it. Have you seen any info on it actually being used and its efficacy?

Edit: I mean the stationary mode where they said they'd run the motor to funnel waste heat to the battery, not actually driving around.

 

[ngogas]

I don’t believe that the 3 does not have some type of heating when it’s idealing to warm the battery up. No way they rely on just drawing battery as away to heat up. I call bs.

 

[j5555]

If you are covered in the range you need the following day--is the std. mobil connector maybe a better option, in that it acts like trickle charger in a sense (staying on all night) , in cold garages, vs the HPWC? Also would allow pre-heating interior while on charge vs using battery and thus range once en-route.

At 4 miles range per hour it would be powered all night vs guessing (and perhaps changing) every day the charge start/completion time to coincide with time of departure.

I have HPWC and charging at 5am to 7am or so I am still getting limited regen at 8am. Garage, unheated, but keep in mind this is only late-October not mid-winter.