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Regeneration

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I know it has turned cold over the last few days, but I have never known the regeneration to be so bad for miles, it is like 50% worse at not slowing down at like 2ºc, I am sure I have driven in as cold or even colder weather since I have had the car, but it seems really bad over the last few days.

Can anyone answer a question, regarding battery capacity and amount of regeneration.

At 90% it is really poor over last few days:-

If I charged to 80% at the same outside temp would I get more regeneration from the start at will it be the same as at 90% I can understand the car having less generation at 100% but to be honest at 90% I would have though it would not change much.

Or is more about the battery temperatures? and makes little difference to battery percentage of charge?

Thought please
 
Below 90% battery level, it’s all about the temperature of the battery cells.

regen is fully back to normal at around 23°C

Assuming outside temp goes down to 5°C, then if the car stays awake overnight the battery stays around 14°C. If it goes to sleep it gets much colder, possible down to the ambient temp (I haven’t measured that lately)

if you turn on climate remotely in the morning 20 mins before you leave, (either when it’s plugged in or not, but it doesn’t do this if charging is active or if you turn on climate from inside the car and stay in it) then the car will warm the battery upto the 23°C for you and you’ll have full regen.
 
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If you turn on climate remotely in the morning 20 mins before you leave, (either when it’s plugged in or not, but it doesn’t do this if charging is active or if you turn on climate from inside the car and stay in it) then the car will warm the battery upto the 23°C for you and you’ll have full regen.

I don't know about full regen but it certainly makes a difference.

I charge on 17kw 3 phase at a location I'm often at for a few days and on 32a commando at home. Also occasionally on 3 pin or 16a. Charging immediately before charger makes a big difference on the higher power ac, much less at 7kw and nearly nothing I reckon at 10-16a.
 
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I am sure I have driven in as cold or even colder weather since I have had the car, but it seems really bad over the last few days.

One thing to bear in mind is that the battery has huge thermal inertia, so it's not the ambient temperature right now that counts - rather the history of temperature where it has been parked. If you didn't drive it far enough on the previous day to get it fully warmed up, then history from the previous day will be carrying over.

With typical UK winter weather, it's either overcast and relatively constant cold-ish day and night, or clear with low temps overnight but warmer in the daytime. So it can often be the warmer days where regen is most limited (because it was correspondingly colder overnight and the car hasn't warmed up yet).

I see this particularly because I park my car to the north of the house where it's shaded from any sunshine, so if I get into the car mid-morning the air temperature may have come well up in the sunshine but the car is still cold-soaked from overnight.
 
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sitrep. bit colder last night. woke up to -1ºC outside temp, 6ºC battery temp (I'd kept it awake overnight by keeping api calls running and sentry mode on)

same routine of turning on climate in the app. It took longer, about 35 mins, to get to the same target battery temp of 23ºC and as soon as it did the power dropped to 2kW (cabin heater) and the power to the front/rear stators dropped to zero.
 
I use the ScanMyTesla app, and a compatible OBDii bluetooth reader.

here are some screenshots and a graph from this morning

20200121.jpg


before
20200121_smt0.jpg


Immediately after turning on climate - front and rear motors are drawing 3kW each to generate heat in the stators
20200121_smt1.jpg


Immediately after the stators stopped drawing power - battery (cell temp mid) at 23.8ºC, coolant inlet higher 32.9ºC and stators at 80-90ºC (and so continued to warm the batteries even after the energy use dropped by keeping the coolant circulating, transfering heat from the stators to the battery cells)
20200121_smt2.png
 
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I use the ScanMyTesla app, and a compatible OBDii bluetooth reader.

here are some screenshots and a graph from this morning

20200121.jpg


before
20200121_smt0.jpg


Immediately after turning on climate - front and rear motors are drawing 3kW each to generate heat in the stators
20200121_smt1.jpg


Immediately after the stators stopped drawing power - battery (cell temp mid) at 23.8ºC, coolant inlet higher 32.9ºC and stators at 80-90ºC (and so continued to warm the batteries even after the energy use dropped by keeping the coolant circulating, transfering heat from the stators to the battery cells)
20200121_smt2.png
Thanks for sharing.

Looks like it took a good >30mins to heat the batteries up, drawing a significant amount of current to do so!

The million dollar question is - was using all that energy to condition the car before driving worth it? Yes, without doing so will impact range but I suspect less range loss than energy spent?
 
The million dollar question is - was using all that energy to condition the car before driving worth it? Yes, without doing so will impact range but I suspect less range loss than energy spent?

It won't be worth it in terms of straight energy in vs miles out. But there may be other reasons, principle among which is that that bit of extra range could avoid a stop for a certain journey. Range increased by the number of miles' worth otherwise used in heating etc and not regenerated because of friction braking could amount to a fair bit. I do a regular journey which in the winter is range challenging and, rightly or wrongly, I often preheat, and/or late charge, for it. Late charging of course is just timing rather than extra energy.