Battery range increasing AFTER charging completes?

[insaneoctane]

Since a firmware change a few months ago (I'll have to dig deeper to identify which firmware it started), I occasionally get in the car in the morning and see the battery is "overcharged" vs my set point. This morning I saw it again. I set SOC to 80% which is normally about 255 miles for me. This morning my range was 267 miles and I checked, it was 84%. So this time I dug into the charge data (which I record via API) and discovered something interesting. My car charged to 80% last night and ended at 4:07am. At that time it was 80% SOC with a range of 257 miles. I looked at my actual EVSE usage data (via CT clamps) and the EVSE stopped charging at 4:07am and DID NOT ADD ANY ADDITIONAL CHARGE. I verified that at no point from 4:07am until I disconnected, there was NO additional power supplied by the EVSE. But, my battery increased in both SOC and range shortly after completing charging. Specifically, my car woke up at 5:30am (don't know why) and at that time, SOC was 84% and range was 269 miles. By the time I drove away, at 7:48am, my SOC was still 84% and range was 268 miles. So, what's strange is the change in SOC and range AFTER charging. This might be explained by thermal effects, but it doesn't explain why is it rare... I only have seen this probably 6 times in the last 2-3 months since it first started happening and I charge every night. Any thoughts? Anyone else see this?

 

[M109Rider]

Never heard of that before. Very strange.
Do you have kids or someone that is playing with the car or your app. ?

You don’t happen to live in amityville do you ...

 

[antoinearnau]

I noticed something similar on 20.4.2.

It always charges a couple percent above the set value.

 

[Bandit]

I've been experiencing the same for the last while. Today for example I finished charging at 75%, then almost immediately drove a few kms to the gym which dropped to 74% and then when I finished at the gym (not charging) it was up to 76%. Shenanigans.

 

[AltLogic]

I have noticed the following over 6 years of EV driving:

If I charge a car when the battery is cool and then the battery gets warmed up externally it shows an increase in range.

If I park a car on a hot day after a long drive in the afternoon, the next morning I have a decrease in range higher than expected vampire losses.

So it could be temperature related.

 

[jdcollins5]

I have seen both an increase and a decrease that I believe it is temperature related. A few updates ago I started seeing more variability in my range miles each time I got in and out of the car so I started taking snapshots of the screen.

I can drive to the gym and back in the morning and say it is mid-80’s. When I get back in the car that afternoon it may be mid-90’s and I have seen as much as a +10 mile increase. The next morning I may see a -5 mile decrease when the temps are back in the low 80’s.

I read a thread where the guy explains that with the chemical composition, the battery and the BMS are very much temperature sensitive. One of his comments was that he thought some of what people were calling vampire drain was just temperature variations between night and day.

 

[Kirby64]

This could just be a battery balancing thing. After the batteries balance themselves, the BMS updates the % to reflect that it's actually higher than it thought it was, perhaps?

 

[M3BlueGeorgia]

Unless it is fully charged or fully discharged, figuring out the percent charge of a lithium-ion is more of an art than a science.

 

[insaneoctane]

I charged to 100% last night to see if it changes anything. Very erratic range drops on the first half of my commute (ie drove 20 miles but lost 40 miles of range) I'll share the data in a day or so.

 

[M109Rider]

I charged to 100% last night to see if it changes anything. Very erratic range drops on the first half of my commute (ie drove 20 miles but lost 40 miles of range) I'll share the data in a day or so.

Just curious, did you charge to 100% last night, and not drive until morning ?

 

[insaneoctane]

Just curious, did you charge to 100% last night, and not drive until morning ?

My charging began at 2:30am. By the time I was ready to drive this morning it showed 322 miles, 30 minutes remaining to charge, but showed 100% so I didn't bother with the last bit of remaining charging. Not sure if the range would have gone up any had I let it fully finish.

 

[insaneoctane]

So, I'm also seeing my SOC rise after arriving home from my daily commute. Interestingly, it seems to be far more common arriving home vs arriving at work. Also, I think this might be the culprit in my high vampire losses at work....specifically, I dropped 11 miles while sitting at work for only 6 hours, but magically gained 9.4 miles back from sitting at home. Look at the graph of my range.....arrive around 9am with 201 miles range, leave at 2:30pm with 190 miles (11 mile lost). Arrive home at 5:30pm with 127 miles, by 6pm range is back up to 137 miles. My range has become VERY volatile with the last 3-5 firmwares....

 

[AlanSubie4Life]

So, I'm also seeing my SOC rise after arriving home from my daily commute. Interestingly, it seems to be far more common arriving home vs arriving at work. Also, I think this might be the culprit in my high vampire losses at work....specifically, I dropped 11 miles while sitting at work for only 6 hours, but magically gained 9.4 miles back from sitting at home. Look at the graph of my range.....arrive around 9am with 201 miles range, leave at 2:30pm with 190 miles (11 mile lost). Arrive home at 5:30pm with 127 miles, by 6pm range is back up to 137 miles. My range has become VERY volatile with the last 3-5 firmwares....

View attachment 433117

Do you have any hills on your commute? There is definitely hysteresis on the miles it credits you from doing regen (it tends to add them in 4-mile increments for whatever reason...). So that could be a factor. It kind of looks like there is a downhill near (but not at) the end of your commute home. But a little hard to tell from your graph - it does not look exactly like what I would expect for a drive that ends with a downhill.

 

[insaneoctane]

Several elevation changes through valleys. BUT, when I return home there is a zero net change. Why would the mileage related to elevation change after the car is parked and why is this behavior new?

 

[AlanSubie4Life]

Several elevation changes through valleys. BUT, when I return home there is a zero net change. Why would the mileage related to elevation change after the car is parked and why is this behavior new?

Sounds like it really does not explain it. I was just saying: the system builds up a hidden reserve of miles when regenerating downhill. It is NOT displayed immediately. It seems reasonable that at some point it might put those miles back on the gauge.

Why the behavior is new? Firmware changes all the time, and there definitely have been BMS adjustments lately, based on the uptick in complaints here.

This observation could also be due to temperature changes as others have suggested. It’s just an estimate, lots of factors, and requires lots of corrections to get a good estimate.

 

[quickstrike12]

@insaneoctane
I’ve seeing similar behavior lately. Stops charging at 80% and then at some point overnight rises a couple more percent. Then after not driving the second day it rose overnight a couple more percent. It’s up to 85% now. im wondering if how high it might go if I didn’t unplug and drive.

Don’t really have a way to check but it almost seems as if it’s getting a bit of trickle charge and adding miles somehow but that seems very unlikely. I don’t think car battery charges unless the car “says” it’s charging. It is cold overnight and warms in the day. I guess this could be a chemical change adding small voltage to cells, and maybe then the BMS recalculates?

Weird. it’s not a problem by any means I’m just very inquisitive by nature and like to understand how things work.

did you ever learn more about this behavior insaneoctane?

 

[insaneoctane]

@insaneoctane
I’ve seeing similar behavior lately. Stops charging at 80% and then at some point overnight rises a couple more percent. Then after not driving the second day it rose overnight a couple more percent. It’s up to 85% now. im wondering if how high it might go if I didn’t unplug and drive.

Don’t really have a way to check but it almost seems as if it’s getting a bit of trickle charge and adding miles somehow but that seems very unlikely. I don’t think car battery charges unless the car “says” it’s charging. It is cold overnight and warms in the day. I guess this could be a chemical change adding small voltage to cells, and maybe then the BMS recalculates?

Weird. it’s not a problem by any means I’m just very inquisitive by nature and like to understand how things work.

did you ever learn more about this behavior insaneoctane?

I've got current measurements on the HPWC and have verified that it is NOT getting additional watts after the charging stops. I have been off for the holidays the last few weeks and haven't been making my daily commute so no real data. I did pick up the gear to monitor the CAN bus and will likely get that operational in January. Hoping to gain additional insight from that. My range has dropped in the last few weeks after I got 40.x. Not happy seeing 80% gives me 245 miles now and hoping it's related to temperatures.

 

[quickstrike12]

Thanks for the info. as it turns out I let it go for most of the day to see how high it would go. But what I realized over on the wall my Tesla HPWC unit had the stream lights going up and down like it was charging. So I used both the app and then the cars screen to verify that it was NOT. It said stopped charging course like always. And showed 0 amperage out of 42 entering the car. So both the car and app confirmed not charging yet the wall charger lights said different. Also the plug itself was flashing the green like it was charging. Oddly it wasn’t increasing at a rate of about 1 mile per 3 to 4 hours. Needed up going from 187 to 201 in total after almost a full day.

Not doing it today after I unplugged and drove. Strangest thing I’ve seen since I’ve owned the car for 2 years.