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Discussion Starter · #1 ·
Hi all,
First time today that I see “stripes” on the power/regen meter on the power side! I guess it indicates that not all the power is available but I really wonder why this can be: temperature was not super cold, battery was decently charges, nothing special on the road or in the car...just plain normal driving. It went away by itself after roughly 30 minutes driving.
Any idea what could limit the power?

here is a pic of this:
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7A95C4F5-4042-41E5-B067-36B9EB552075.jpeg


To be fair, I did not notice any difference in the power or in the way the car was but still I wonder why the power is limited :)
 

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Yup, cold battery. Totally normal.

I live in an area where "freezing" is ~50F, and the car stays in a garage yet regen is always limited when I start driving because the battery is cold.
 

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Discussion Starter · #4 ·
Limited regen I have seen already and indeed due to cold but here the regen wasn’t limited, only peak power. It was 5 degrees Celsius (41 degrees Fahrenheit) which is not super cold let say.

So regen can be full but not the power? Seems strange to me but ok :)
 

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FWIW the manual at support.polestar.com covers the stripy lines and what they mean. Although they're vague...
 

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yet regen is always limited when I start driving because the battery is cold.
Regen is limited when you begin a journey if your battery has been topped up. You can't regen into something that is full. And so the system will dump the power and make you use the friction brakes. As you drive and use up battery charge you will see the regen area get larger and the friction area get smaller. Speed also affects this. If you are going slowly there is not nearly as much regen available in your motion and so the regen area will get smaller.
 

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Regen is limited when you begin a journey if your battery has been topped up. You can't regen into something that is full. And so the system will dump the power and make you use the friction brakes. As you drive and use up battery charge you will see the regen area get larger and the friction area get smaller. Speed also affects this. If you are going slowly there is not nearly as much regen available in your motion and so the regen area will get smaller.
Interesting. I’ve never thought about how the car might “dump” the power. I mean, what’s actually physically happening there? I assume something other than the brakes must heat up. The motor itself? Does something “disconnect” or is there a circuit onto which the current is offloaded safely?
 

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Interesting. I’ve never thought about how the car might “dump” the power. I mean, what’s actually physically happening there? I assume something other than the brakes must heat up. The motor itself? Does something “disconnect” or is there a circuit onto which the current is offloaded safely?
I believe it knows how much it can put back in the battery and the regen simply disengages the motor reversing (which does the regen) and engages the friction brakes instead.

Someone else may have a more technical explanation than that.
 

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I believe it knows how much it can put back in the battery and the regen simply disengages the motor reversing (which does the regen) and engages the friction brakes instead.

Someone else may have a more technical explanation than that.
I understand the motors to be permanent magnet motors, which to me means they are unable to “disengage” and therefore whenever the wheels turn electricity is either being spent or regenerated. That’s why they’re relatively inefficient cars (can’t run on one motor only). I’m sure there is a simple answer that I’m too naive to have considered.
 

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The permanent magnets will always induce a voltage when being turned, but as long as you don't pull a current, you don't pull energy from the system.

The car simply switches to mechanical brakes when the BMS can't pump any (more) energy into the battery. No voodo and/or rocket science involved.
 

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Don't be so quick to deny it, Heinwald... You will have to get in your car late one night... You don't want a 'passenger' to join you, do you?
 

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Regen is limited when you begin a journey if your battery has been topped up. You can't regen into something that is full. And so the system will dump the power and make you use the friction brakes. As you drive and use up battery charge you will see the regen area get larger and the friction area get smaller. Speed also affects this. If you are going slowly there is not nearly as much regen available in your motion and so the regen area will get smaller.
True, I didn't think about this since the regen limit isn't much. It's a pretty small sliver that's unavailable.
 

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Discussion Starter · #18 ·
A topic on the peak power is now becoming a regen topic :cool: and not to mention the voodoo aspect of it :eek:

So, on the peak power: we are sure it is due to temperature? If so, then temperature can limit the peak power without impacting the regen capacity? And that would be because regen is putting back way less energy that what peak power pulls out of the battery? Would make sense indeed!
 

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A topic on the peak power is now becoming a regen topic :cool: and not to mention the voodoo aspect of it :eek:

So, on the peak power: we are sure it is due to temperature? If so, then temperature can limit the peak power without impacting the regen capacity? And that would be because regen is putting back way less energy that what peak power pulls out of the battery? Would make sense indeed!
I'm not sure, but it seems the most likely. Batteries operate at their most efficient at certain temps, so that will impact charging/power, but the car's brain is probably doing most of the work. I'm loathe to compare a car to a phone, but the battery tech is mostly the same, and the current flow to and from the battery is mostly managed by circuitry in the device, not the battery itself. Li-ion batteries tend to get violent if they aren't happy, as Samsung is well aware. Kudos actually to Tesla for showing that they can be safe in a car, that was a huge step.

This is all healthy speculation, but testing regen vs power when the battery is hot is pretty easy: just visit your local racetrack and get in a bunch of hot laps. :)
 
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