Polestar Forum banner
1 - 16 of 16 Posts

·
Registered
Joined
·
772 Posts
Discussion Starter · #1 ·
The power meter on the right side of the instrument panel shows whether current is being drawn from or regenerated back to the battery. Sometimes (and sometimes not) there are gray stripes on the the far side of the regenerative direction, indicating that (according to the manual) "regeneration to the battery is limited". Note that these are different from the orange stripes, which occur if you brake so firmly that you exceed the regenerative braking capability.

Question: I've noticed that the presence and horizontal extent of these bars varies over time. Sometimes they are not present at all. I'm wondering what causes the variation. A few guesses:

1) State of charge. For example, I imagine that if the battery is charged to 100%, the gray bars would cover the entire left side of the power. meter, since no regenerative charging would be possible. I've never charged to 100%, though, so I don't know. But what about 95%, etc.?

2) Battery temperature. It does seem (?) that the gray bars are more likely to appear when the battery is cold. Perhaps the ability to push current into the battery is limited at low battery temps (seems logical).

Thoughts on my guesses? Other ideas?
 

·
Super Moderator
Polestar 2, Midnight (blue), charcoal interior, non-PP
Joined
·
2,877 Posts
Correct on both counts. When the battery is cold, or too hot, or too full, or too empty, regen and power delivery are capped. On my first drive today I had a bit of limit on the regen side, but a quick boot out of our side road soon saw that disappear!
 

·
Super Moderator
Polestar 2, Midnight (blue), charcoal interior, non-PP
Joined
·
2,877 Posts
It's the same on all EVs, regen is almost non-existent when near 100% charged, or below about 5% which is of course exactly when you need it most!
 

·
Registered
Joined
·
179 Posts
Does the P2 blend in friction braking if regen is limited? That’s one of the things I really like about the BMW i3 - it blends in friction braking at 100% SOC so that one-pedal-drive feel is consistent regardless of SOC.
 

·
Super Moderator
Polestar 2, Midnight (blue), charcoal interior, non-PP
Joined
·
2,877 Posts
Yes, basically the car knows how much regen is available and when to start blending in the mechanical brakes; this transition point changes depending on how much regen is available therefore. Doing this smoothly is massively challenging from a software point of view as if you get it wrong then the transition isn't smooth and many early EVs had big problems in this area. The Ampera (= Chevy Volt) wasn't great at this for instance, particularly when coming to a stop. The Polestar seems far better.
 

·
Registered
Joined
·
2,227 Posts
2) Battery temperature. It does seem (?) that the gray bars are more likely to appear when the battery is cold. Perhaps the ability to push current into the battery is limited at low battery temps (seems logical).
I've only every charged to 90%. When new I never got the bars as the weather was warm. Once the night temps dropped below 10deg I started to get Bars on the Left only.

Only recently once the temp dropped below 3deg did I see bars on the right.

I suspect that bars on the right (power) are 100% temp only. The bars on the Left (regen) are mostly temp unless you are at 100deg - however as I've never been at both above 18deg and 100% charge it's hard to say 100%.
 
  • Like
Reactions: rgledhill and JPC

·
Registered
Joined
·
182 Posts
I haven't seen any evidence so far of regen being reduced when cold - I have been in colder temperatures and had full regen and had limited regen in warmer temperatures. It's not been that cold yet here though really (mostly above 0C).

I think it might actually be due to the algorithm that uses friction braking to clean the brake discs if they are rusty? i.e. if it's been wet and I haven't driven the car for a while, it shows less regen?

I also think that regen will be limited when the car is charged to 100%.
 

·
Registered
Joined
·
176 Posts
I think it is interesting that as you come to a halt (with OPD set to standard) that the last couple of metres use the friction brake - going forwards and backwards. Presumably this occurs because straight regen would take a much longer distance to stop.
 

·
Super Moderator
Polestar 2, Midnight (blue), charcoal interior, non-PP
Joined
·
2,877 Posts
It's impossible to stop just with regen as the available energy out of the motor (i.e. the retardation) drops with speed so you end up with an asymptotic curve where it will only reach zero mph at infinity. In other words the last few miles an hour have to either use the physical brakes, or alternatively the software actually drives the motors backwards a bit to finish the slow-down. On the Kona, the early versions of the software didn't judge it quite right and if you lifted off the brakes just as it came to a stop going forwards, the car would roll backwards 6 inches due to the reverse motor driving!
 

·
Registered
Joined
·
772 Posts
Discussion Starter · #12 ·
Regen is definitely curtailed with a cold battery. The other week, it was -3C and I had 80% charge and my entire regen was unavailable. It gradually became available over the next 15 mins or so.
Yeah, I had the identical situation today. I'm amazed at how transparent the regenerative vs friction braking is. Very hard to tell the difference (at least for a noob like me).
 

·
Registered
Joined
·
194 Posts
Regen is definitely curtailed with a cold battery. The other week, it was -3C and I had 80% charge and my entire regen was unavailable. It gradually became available over the next 15 mins or so.
I routinely get limited regen until the battery pack has warmed up, and you can see the regen slowly getting less the longer you drive. A few big regen‘s e.g. going downhill and slowing down soon takes some chunks off the limit.
 

·
Registered
Joined
·
2,227 Posts
Regen is definitely curtailed with a cold battery. The other week, it was -3C and I had 80% charge and my entire regen was unavailable. It gradually became available over the next 15 mins or so.
I had that too ... I floored it 2-3 times and it went down to 10% very fast. Great to see the heating take an effect!
 

·
Super Moderator
Polestar 2, Midnight (blue), charcoal interior, non-PP
Joined
·
2,877 Posts
Best way to get the battery up to temperature is a bit of flooring and regening - get rid of those grey lines :).
 
1 - 16 of 16 Posts
Top