Battery preheat released

[mknox]

Battery preheat feature further reinforces my belief that 30 amp public L2 chargers are woefully inadequate in cold climates. My -15ºC cold-soaked car drew 38A @ 237V for a good 15 minutes this morning. And I still didn't have a battery warm enough to use regen.

I only charge at 30 amps at home, and it seems to work okay for me. After about 1/2 hour I have somewhere near half re-gen capability. Personally, I don't mind reduced re-gen in the winter anyway.

But yes, I will seek out higher power public chargers (80 amps to take advantage of my car's 80 amp capability, if I can find it), but that has more to do with charging speed than anything else.

 

[rypalmer]

I only charge at 30 amps at home, and it seems to work okay for me. After about 1/2 hour I have somewhere near half re-gen capability. Personally, I don't mind reduced re-gen in the winter anyway.

But yes, I will seek out higher power public chargers (80 amps to take advantage of my car's 80 amp capability, if I can find it), but that has more to do with charging speed than anything else.

I've been working on a tool to help annotate Plugshare listings with their max amperage. I'm still collecting training data, if anyone cares to help

Location Classifier

 

[wayner]

Curious what SOC the car had when you left the house?

I think it was about 85% - the SoC should not have been a factor - at least I wouldn't think so.

 

[Peter_M]

I tried pre-heating and charging on a 14-30 outlet at -20C a few days ago (with the new software). In 1.75 hours, the charge level went from 54% down to 53%. And later on a 60A HPWC, I saw 8kW for pre-heating without trying to charge. So yes, 30A can heat the battery on a cold day OR charge but not both at the same time.

 

[Peter_M]

I've been working on a tool to help annotate Plugshare listings with their max amperage. I'm still collecting training data, if anyone cares to help

Location Classifier

Getting off topic here, but how is that different from the "Max Volts" and "Max Amps" that is already there in the checkin page on PlugShare?

 

[rypalmer]

Getting off topic here, but how is that different from the "Max Volts" and "Max Amps" that is already there in the checkin page on PlugShare?

Those fields are rarely used in check-ins, and there's no way to filter the map of chargers by amperage even when they are.

 

[Peter_M]

Those fields are rarely used in check-ins, and there's no way to filter the map of chargers by amperage even when they are.

I see. I'd like to see the max reported power for a station and be able to filter by power (not current). And will you use the checkin data that is already there on PlugShare?

 

[David99]

Battery preheat feature further reinforces my belief that 30 amp public L2 chargers are woefully inadequate in cold climates. My -15ºC cold-soaked car drew 38A @ 237V for a good 15 minutes this morning. And I still didn't have a battery warm enough to use regen.

I agree. When preheating the car draws arpox 10 kW. On a 30 Amp charger, you would lose charge!

 

[mrElbe]

Preheating car in drive way last Sunday morning at -27 C outside temperature drew 48 Amps.

 

[Struja]

This preheating thing is strange to me. My car is garage parked, but by garage is only partially insulated so today, the car's temp was at +1. I started to preheat at 7:40am. I preheated until 8:25am. Car was plugged in the entire time.

Got in the car and I only had about 1/2 regen permitted. I just figured after 45 minutes of preheating, it would have warmed up sufficiently to allow for full regen. I also figured that it wasn't that cold inside the garage.

I then drove to work which is only a short 10 minute drive and I never got to full regen. Not really a big deal, but I figure I might be doing something wrong.

 

[mknox]

I agree. When preheating the car draws arpox 10 kW. On a 30 Amp charger, you would lose charge!

For some reason, I am not seeing this, unless I misunderstand. Are you saying activating pre-heat and trying to charge at the same time? If so, I guess this could happen, however, I have not personally seen pre-heating draw more power than the HPWC can provide, so it should be more like no charge, not lose charge. Another observation is that even when my car is cold-soaked at -20C, the battery heating (and associated icon on the app) only seems to run for, maybe 5 or 10 minutes before shutting off.

I tend to charge overnight with it timed to end maybe a hour or two before I leave in the morning. Before I jump in the shower, I activate the HVAC on the app, and all is well when I go out to my car.

 

[mknox]

Got in the car and I only had about 1/2 regen permitted. I just figured after 45 minutes of preheating, it would have warmed up sufficiently to allow for full regen. I also figured that it wasn't that cold inside the garage.

See my post above. I have observed that the battery heating does not run for very long and I too see about 30 kW re-gen limits (about half) no matter if I leave the HVAC on for an hour or 20 minutes. I think this is by design to give "some" battery conditioning without wasting too much electricity.

 

[Peter_M]

For some reason, I am not seeing this, unless I misunderstand. Are you saying activating pre-heat and trying to charge at the same time? If so, I guess this could happen, however, I have not personally seen pre-heating draw more power than the HPWC can provide, so it should be more like no charge, not lose charge. Another observation is that even when my car is cold-soaked at -20C, the battery heating (and associated icon on the app) only seems to run for, maybe 5 or 10 minutes before shutting off.

I tend to charge overnight with it timed to end maybe a hour or two before I leave in the morning. Before I jump in the shower, I activate the HVAC on the app, and all is well when I go out to my car.

See my post #64 above - I lost charge on a 14-30 while pre-heating and trying to charge.

 

[mknox]

ISo yes, 30A can heat the battery on a cold day OR charge but not both at the same time.

See my post #64 above - I lost charge on a 14-30 while pre-heating and trying to charge.

Right. Question for the group: Common wisdom was that charging had the side benefit of heating the battery at the same time anyway, and that's why it's good practice in wintertime to try and end your charging cycle just before you plan to head out. What would be the advantage of consciously turning on pre-heating while you're trying to charge? The only answer I can think of is because you want to warm the cabin up too... in which case separating battery heating from cabin heating in the controls would be a good idea.

 

[Peter_M]

Right. Question for the group: Common wisdom was that charging had the side benefit of heating the battery at the same time anyway, and that's why it's good practice in wintertime to try and end your charging cycle just before you plan to head out. What would be the advantage of consciously turning on pre-heating while you're trying to charge? The only answer I can think of is because you want to warm the cabin up too... in which case separating battery heating from cabin heating in the controls would be a good idea.

Good question - I would assume turning on pre-heat would heat the battery more/faster than just charging, but I can't say I've got solid evidence of that. If you just want a warm cabin and the most energy-efficient approach and you aren't trying to stretch your range, maybe a good strategy would be to try to time your charging to be done just when you're ready to leave, and turn on cabin heating just 5 minutes before you go to warm up the interior. I agree - separate controls would be great.

 

[Doug_G]

See my post #64 above - I lost charge on a 14-30 while pre-heating and trying to charge.

It used to be that charging at 110V in extreme cold (below about -15C IIRC) would actually deplete the battery instead of charging it. At those temperatures there isn't enough power to warm the pack sufficiently to start charging. Tesla updated the algorithms to prevent range loss from happening.

Sounds like you found a hole in the algorithm - doesn't take preheat into account.

 

[wayner]

It would be nice if the app/API had the ability to show you the regen status of the car and then allow you to decide whether you wanted to heat the battery more to deal with that.

 

[IT Geek]

It would be nice if the app/API had the ability to show you the regen status of the car and then allow you to decide whether you wanted to heat the battery more to deal with that.

It would be nice if the App allowed you to schedule the recharge so that the car was finished charging at a given time each day. Some might want to start their charging at 4:00 in the morning all the time, but I'd rather see it finish at 7:30. Yeah, I know there's an App for that..but I think this should be a Tesla feature.

 

[mknox]

It used to be that charging at 110V in extreme cold (below about -15C IIRC) would actually deplete the battery instead of charging it. At those temperatures there isn't enough power to warm the pack sufficiently to start charging. Tesla updated the algorithms to prevent range loss from happening.

I actually never saw that happen, but I cannot recall if I was actually at or below -15C . If I plugged in to a 120 volt outlet when the car was very cold, there would be 12 amps of power draw, but no increase to my SOC. I assumed it was using all 12 amps to run the heater, which was never enough to get the battery to the point where it could charge. I did this a few times at my daughter's place in Illinois during the winter after the car had sat outside for a few days.

But... if I was travelling in the winter and the hotel only had a 120 volt outlet, as long as I plugged in as soon as I arrived (car fully warmed up from long trip), I would actually see 3-5 km/h of charging overnight and my battery would be "warm" in the morning. I have done this several times in temperatures well below freezing, but again, not sure if it was quite -15C cold or not. I was very pleasantly surprised by this because all I was expecting at 120 volts was for the warmed up car to hold it's own overnight.

 

[mknox]

It would be nice if the App allowed you to schedule the recharge so that the car was finished charging at a given time each day. Some might want to start their charging at 4:00 in the morning all the time, but I'd rather see it finish at 7:30. Yeah, I know there's an App for that..but I think this should be a Tesla feature.

Indeed. The Chevy Volt has had this capability since 2012.