Roadster battery heating

[znino]

Today my roadster spent a good part of the day outside. The temperature was around -11C. When I got into it this evening, the No Regen light was on and I assumed that this was because the battery was too cold to put electrons back in. I drove home, about 25 Km, highway and still the Regen light was on. In the past, when I have seen this happen it seems to me that after 10-15 minutes of driving the Regen would be back again. As I got home I decided to check the temperature of the battery with the OVMS module. It was at +7C. I plugged the car in and it said Heating battery instead of charging. I have never noticed that in the past (but maybe I never paid attention). After about 30 min I checked it again and the battery was at +13C and still saying Heating. Now, after about 45 min it financially has started charging the battery and the temp of the battery is at +12C. All seems bizarre. Why would it be a degree colder than 15 minutes ago? Does anyone know what the cutoff battery temperature is for the car to use Regen? Seems to be around +13C or so. So strange that I would only have noticed such a case on my 3rd winter!

 

[Doug_G]

Pretty sure anything above freezing gives you regen.

 

[znino]

Pretty sure anything above freezing gives you regen.

You mean battery temperature above 0? If that's the case then it shot have been doing regen when I checked and saw it at 7. Maybe something is wrong with the battery temperature reading or something else. Hmmm

 

[djp]

Strange, I've charged with a pack temp reading of 7C before with no battery heating. I thought the cutoff on the Roadster was 0C.

I've only had regen disabled once due to cold, but my car lives in an insulated garage. The one time it happened to me, the battery was cold-soaked overnight in -10C temperatures. The regen came back after about 20 mins of highway driving.

 

[znino]

Strange, I've charged with a pack temp reading of 7C before with no battery heating. I thought the cutoff on the Roadster was 0C.

I've only had regen disabled once due to cold, but my car lives in an insulated garage. The one time it happened to me, the battery was cold-soaked overnight in -10C temperatures. The regen came back after about 20 mins of highway driving.

Yes, that is why I found it odd today. ok, the car was out sitting all day in cold temps but my drive home was 40 minutes and it never came back to Regen. Will have to monitor i guess. Now the battery is in heated garage and no longer battery heating but charging normally.

 

[hcsharp]

In my experience regen shuts off between 6 and 8C, and it maintains that temperature while plugged in and heats to that before charging. It's definitely above 0C. Keep in mind that is the reading for the coldest brick. I believe OVMS displays the warmest brick (somebody correct me if I'm wrong). So in your case the pack was probably a little out of balance thermally. Some bricks were as warm as 13C (displayed on OVMS) while others were 4 or 5C. When it finally started charging your coldest bricks had warmed up while the warmest had cooled to 12C.

 

[znino]

In my experience regen shuts off between 6 and 8C, and it maintains that temperature while plugged in and heats to that before charging. It's definitely above 0C. Keep in mind that is the reading for the coldest brick. I believe OVMS displays the warmest brick (somebody correct me if I'm wrong). So in your case the pack was probably a little out of balance thermally. Some bricks were as warm as 13C (displayed on OVMS) while others were 4 or 5C. When it finally started charging your coldest bricks had warmed up while the warmest had cooled to 12C.

Makes sense. Thanks

 

[Doug_G]

In my experience regen shuts off between 6 and 8C, and it maintains that temperature while plugged in and heats to that before charging. It's definitely above 0C.

Curious. In my experience the Roadster can tolerate lower temperatures for longer than the Model S, without regen limits. Probably in part because the pack is much less exposed. The only way I get a cold regen limit on my Roadster is a lengthy cold soak with temperatures significantly below freezing.

 

[bart513]

Over the past week in NY with temps between 11and 14 degrees F the regen light stayed on between 10 and 30 minutes while driving.

 

[dhrivnak]

I too have lost regeneration with the many cold days and when below freezing for many hours the battery begin to heat as soon as I plug in. It did not happen to me the last two winters but this one has been colder than normal.

 

[sethr]

Something I found odd - on two occasions on different days, I was parked (and cold soaked for 5 hours each time) at 12 degrees F., and another day at 33 degrees F., then drove the same route home. The regeneration limit light went off after almost exactly the same distance/time. You would think it would have regained regeneration sooner when it was at 33 as opposed to 12 degrees.

 

[markwj]

Could range mode, high SOC, be a factor?

 

[Doug_G]

I find the Roadster takes quite a long while to cold soak, probably because the battery pack is a large heavy brick - as opposed to the flat Model S battery pack which has a huge exposed area. I've also found that the car cools down much faster on a windy day, as opposed to a calm, sunny day. So it is possible depending on other weather factors that your battery pack wasn't really that much colder on the 12 degree days.

 

[sethr]

Could range mode, high SOC, be a factor?

I always charge in standard mode, so that's not it...

I find the Roadster takes quite a long while to cold soak, probably because the battery pack is a large heavy brick - as opposed to the flat Model S battery pack which has a huge exposed area. I've also found that the car cools down much faster on a windy day, as opposed to a calm, sunny day. So it is possible depending on other weather factors that your battery pack wasn't really that much colder on the 12 degree days.

Unfortunately, I don't remember if it was sunny or cloudy; windy or not - so maybe that's the answer. Thanks.

 

[ViperDoc]

. Now, after about 45 min it financially has started charging the battery and the temp of the battery is at +12C.

So the charging was free up until the 45 minute mark, when you had to start paying for it?