Charging target creeping up

[WalterG]

Has anyone else seen this? I have been setting charging with a timer to 85% and it's actually worked fine. Until recently... About a week ago instead of charging to 85%, it went to 86%. I didn't really think much of that. Then over the past couple of overnight charges, it has crept up to 87% and today ended at 89%. Anyone else seeing this? I'm kind of wondering if it is related to cold weather and maybe trying to compensate for the cold?

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[bosch88]

It has happened to me... it would normally get 2-3% over the set limit. Not sure why, the few weeks have been 6-10 degrees C here.

 

[Scandinavian]

Has anyone else seen this? I have been setting charging with a timer to 85% and it's actually worked fine. Until recently... About a week ago instead of charging to 85%, it went to 86%. I didn't really think much of that. Then over the past couple of overnight charges, it has crept up to 87% and today ended at 89%. Anyone else seeing this? I'm kind of wondering if it is related to cold weather and maybe trying to compensate for the cold?

Did you have the car outside and what was the temperature during the night compared to the morning?

I have seen a difference 3% higher than the target set in our car. But I then checked the night temperature and it was close to freezing during the night when I charged. The higher number observed was after preheating the car before leaving.

 

[WalterG]

Did you have the car outside and what was the temperature during the night compared to the morning?

I have seen a difference 3% higher than the target set in our car. But I then checked the night temperature and it was close to freezing during the night when I charged. The higher number observed was after preheating the car before leaving.

It’s in the garage so it is probably 40 - 45F vs 20F outside. I also do have climate on so it is preheating. But it seems odd to me that while it is plugged in it still “over charges” slightly to compensate for either the cold or preheating. Seems like it should just divert some of the wall power to that vs charge past the set point. It is only a couple of percent but just seems odd. I also wondered if the % might be off because of the cold - basically as the temp drops the % displayed is a little off? I am going to set to 80% for a while to see what happens.

 

[NC_Taycan]

On a different thread someone mentioned that if the car doesn't reach the target charge by the target departure time it continues charging and may charge past the set point. I haven't seen this but my departure timer is also set to the end of the preferred charging times in the profile - assuming it's honoring those it should stop. I haven't encountered either issue (not reaching the set charge, or charging past the target charge or time).

 

[epirali]

Another potential reason may be cell balancing. Cell balancing is a process of charging some cells while draining others to make sure the entire pack is in optimal balance. It is theoretically possible to go over the charge slightly by balancing.

 

[wmras]

Another potential reason may be cell balancing. Cell balancing is a process of charging some cells while draining others to make sure the entire pack is in optimal balance. It is theoretically possible to go over the charge slightly by balancing.

The charge level difference may be due the temperature difference between when charging stopped and the current temperature.

 

[epirali]

The charge level difference may be due the temperature difference between when charging stopped and the current temperature.

The reason I posted about balancing is I have on occasion seen a 1 or 2% miss in the same environment right at end of charging. This would not be difference in temperature, but the balancing is triggered as needed, so it won’t happen all the time.

Depending on algorithm used the balancing is usually performed at the END of charging cycle for optimal performance.

 

[r553]

One time I was treated to a 90% home charge even though I have it set to 85%. Subsequent charges have been to 85%.

 

[Scandinavian]

It’s in the garage so it is probably 40 - 45F vs 20F outside. I also do have climate on so it is preheating. But it seems odd to me that while it is plugged in it still “over charges” slightly to compensate for either the cold or preheating. Seems like it should just divert some of the wall power to that vs charge past the set point. It is only a couple of percent but just seems odd. I also wondered if the % might be off because of the cold - basically as the temp drops the % displayed is a little off? I am going to set to 80% for a while to see what happens.

I have had a similar experience with pre heating. I am going to do some tests with preheating.

I have tried once to preheat the car while plugged in. I set the the time for preheating in the car, with the battery charged to 85% as target and achieved in the morning. I set the pre heating only and no charging target etc. I wanted to try to see how much power the car would draw from the network. To my surprise the car started also to charge above the set charge target, but at a very low rate. About 40% of the normal charge rate. And from the network it only drew 50% of the available 11 kW?? Very surprised at this.

 

[Gogs]

I’m seeing this as well. Always seems to be when a timer is set. It’s not worrying me but I dint quite understand why I set it at 85% and it charges to 87%.

 

[Kingske]

I’m seeing this as well. Always seems to be when a timer is set. It’s not worrying me but I dint quite understand why I set it at 85% and it charges to 87%.

Just a guess: maybe the timed charger switches off at the initially predicted time and not at the target SoC%? If the charging time is predicted early on based on the effective charge rate and that rate afterwards drifts higher the actual SoC% at the predicted shut-off time will be higher than initially expected? Si non e vero e bene trovato, I suppose...

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