Battery % increases when driving

Faults and Technical chat for the CUPRA Born
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TheBornIDentity
Posts: 192
Joined: Mon Jul 18, 2022 5:55 pm

Post by TheBornIDentity »

Bit of an odd one this…

Quite often when using my home charger I end up with more charge in the car after I’ve disconnected it and driven about a bit. Say, for example, I charged to 80% and then drive a mile or two down the road, the indicated charge sometimes increases by up to 2%.

I don’t live at the top of a steep hill, it’s pretty flat and this never happened with my ID3. If it was just 1% then I’d put it down to the charge level nearly being there but just not quite enough to flip over, but not 2%. I’ve also seen it going from 80% to 81% then 82% but I don’t end up with a higher % at the destination on my regular commute.

I’m just wondering if anyone else has seen this sort of thing happen? I know there is a recall on some ID3’s due to some bad battery modules being at a different voltage to others and perhaps it’s not just those that are affected. My Cupra has done this since I bought it, but I thought it was probably just something to do with the newer software.

davmatjo
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Post by davmatjo »

Mine also displays exactly the same behaviour
TheBornIDentity
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Post by TheBornIDentity »

davmatjo wrote: Sat Oct 01, 2022 8:01 pm Mine also displays exactly the same behaviour
How strange; I was expecting nobody else to have this but your reply was almost immediate, thanks. Hopefully it’s really common and just a software bug.

Mine is booked in for some other warranty stuff next month so depending on what happens in this thread I might ask them to do a battery health check at the same time… looking like I won’t need to though 🤞
Nacaduct
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Post by Nacaduct »

I set the charging limit to 80%, and frequently end up with 85%, or even 87%…

Has also happened that percentage increased 1% while driving. Guess Cupra have to figure their BMS out a bit better?
Cupra Born since ‘22
TheBornIDentity
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Post by TheBornIDentity »

Nacaduct wrote: Sat Oct 01, 2022 8:24 pm I set the charging limit to 80%, and frequently end up with 85%, or even 87%…

Has also happened that percentage increased 1% while driving. Guess Cupra have to figure their BMS out a bit better?
I’ve never had my car charge over the limit set in the cars
E-manager options, even on Rapid chargers. That definitely sound like a fault if setup correctly. It should look like this on the app:

536C00B6-3628-4D0D-901D-28A729158A80.png

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Daveion
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Post by Daveion »

davmatjo wrote: Sat Oct 01, 2022 8:01 pm Mine also displays exactly the same behaviour
Mine is the same. Often rises to 82% after a couple of miles from an 80% charge.
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monkeyhanger
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Post by monkeyhanger »

Mine has crept up by 1 or 2% before, definitely not 5 or 7%. I've attributed my rise to charging overnight in cool conditions and the first I see of the car is when the ambient temp has gone up by as much as 7C.

This potential to rise is why we have a headspace in the battery capacity (58kWh useable, 62kWh actual) .
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TheBornIDentity
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Post by TheBornIDentity »

Thanks for the replies. Looks like it is normal then. 👍
Born2Ride
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Post by Born2Ride »

There is a lot to understanding batteries and BMS calculations and it's difficult to predict actual energy stored. The car is reporting its best guess at capacity at a given time based on many factors such as temperature, battery pack ageing, how you're driving, how much energy the car is using beyond simply driving (heating primarily) and so on. As others stated, if you charge when cold then drive when warm, you will see an increase in reported capacity and you will see this with any li-ion battery. It will run longer when warmer and when the pack is massive (in a car), the effect is more obvious. Similarly you may notice a reduction in capacity when the car is driven cold, the battery will not perform as efficiently.

The comment about rising capacity is why we have usable vs actual capacity isn't right but I can see why someone could think that. Capacity itself does not change when the temperature rises, it just makes the charge flow through the battery more easily. To labour the point, the capacity the car is reporting is a best guess based on current conditions, to help the user have an estimate of when it will need charging. The battery has reserve capacity for two reasons. Firstly, by not charging to full capacity the battery isn't stressed so much and that helps it with a longer life, if you practice the same thing with a phone battery it will last appreciably longer (i.e. life in months, not duration in hours each cycle). Secondly, as the battery ages and capacity is irreversibly lost, the car can start to add some of this reserve capacity back so the capacity remains at 100% and range isn't reduced. Eventually as ageing gets really notable, then the full capacity will be used and your total range will start to diminish. Hopefully with careful management of your vehicle this will be after many years.

Some quick tips to prolong the battery life. Charge via a regular 7-11kW whenever possible, charging slowly make a big difference to battery health. If you only fast charge (50kW+) it will impact battery life. The other thing that makes a big difference is to avoid charging to full each time, I personally aim for about 70% on a charge and only go above when I have a long journey planned.

My experience comes from having a Model 3 for a few years and working in the battery world for over 10. Hope this is helpful.
TheBornIDentity
Posts: 192
Joined: Mon Jul 18, 2022 5:55 pm

Post by TheBornIDentity »

Born2Ride wrote: Sun Oct 02, 2022 9:32 am There is a lot to understanding batteries and BMS calculations and it's difficult to predict actual energy stored. The car is reporting its best guess at capacity at a given time based on many factors such as temperature, battery pack ageing, how you're driving, how much energy the car is using beyond simply driving (heating primarily) and so on. As others stated, if you charge when cold then drive when warm, you will see an increase in reported capacity and you will see this with any li-ion battery. It will run longer when warmer and when the pack is massive (in a car), the effect is more obvious. Similarly you may notice a reduction in capacity when the car is driven cold, the battery will not perform as efficiently.

The comment about rising capacity is why we have usable vs actual capacity isn't right but I can see why someone could think that. Capacity itself does not change when the temperature rises, it just makes the charge flow through the battery more easily. To labour the point, the capacity the car is reporting is a best guess based on current conditions, to help the user have an estimate of when it will need charging. The battery has reserve capacity for two reasons. Firstly, by not charging to full capacity the battery isn't stressed so much and that helps it with a longer life, if you practice the same thing with a phone battery it will last appreciably longer (i.e. life in months, not duration in hours each cycle). Secondly, as the battery ages and capacity is irreversibly lost, the car can start to add some of this reserve capacity back so the capacity remains at 100% and range isn't reduced. Eventually as ageing gets really notable, then the full capacity will be used and your total range will start to diminish. Hopefully with careful management of your vehicle this will be after many years.

Some quick tips to prolong the battery life. Charge via a regular 7-11kW whenever possible, charging slowly make a big difference to battery health. If you only fast charge (50kW+) it will impact battery life. The other thing that makes a big difference is to avoid charging to full each time, I personally aim for about 70% on a charge and only go above when I have a long journey planned.

My experience comes from having a Model 3 for a few years and working in the battery world for over 10. Hope this is helpful.
Interesting, thanks.
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