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Usable battery capacity not included in range estimate

turok3000

Member
Mar 18, 2019
137
120
Seattle, WA
Hi,

I noticed around a month or so ago whilst supercharging to 100% that, once I reached 100%, it continued to charge for over 20 mins. I had places to go so stopped it manually and moved on. Recently, I thought I would retry this to see if it happened again so I supercharged to 100% and then, sure enough - it continued to charge for another 29 minutes before it eventually stopped. (Teslafi recorded charging stats showing this attached.)

Note, this is not a %age energy vs range display thing - I toggled between the two display options several times whilst this was happening - the range hit 295 miles at 100% and didn't rise any further despite the battery continuing to charge.

The fun part is that this did appear to result in more usable capacity - see my attached trip usage for the first 4 miles after leaving the charger - it stayed at 100% and teslafi stats also show the range staying at 295 for the first 10 minutes of the drive.

My take away is that I appear to have a few percent capacity above "100%" which I can both charge up and run down by using the car.

Has anyone else seen this or, even better, know how I might trigger a recalibration to realign display "100%" with the real 100% ?

Thanks
 

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jdcollins5

Member
Aug 14, 2018
760
491
Wilmington, NC
Once the battery reaches 100% and continues to charge is due to the BMS balancing cells. Some cells reach max volts before others so the BMS discharges some while it charges others in order to balance all cells. This will increase the full usable capacity of the battery.

I have seen where the miles does not increase but you can drive a few miles before the miles begin to decrease. You should see an increase in range miles during your next charge due to the increase in usable capacity due to the cell balancing.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,682
11,655
San Diego
Has anyone else seen this or, even better, know how I might trigger a recalibration to realign display "100%" with the real 100% ?

I haven't seen that behavior of the Trip Planner, but as @jdcollins5 says, let us know what your projected 100% capacity is now when you are charged to 90%. It does seem likely that it might readjust to be a few miles higher after that charge. But who knows - if it knew it had more capacity I don't see why it wouldn't just increase the rated miles at 100% right away, but you didn't see that. I have seen a few people report somewhat different behavior when using a Supercharger to charge to 100%. But I've never stuck around long enough at a Supercharger to know how it behaves typically.
 
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turok3000

Member
Mar 18, 2019
137
120
Seattle, WA
Thanks for the feedback.

Unfortunately, capacity has only gone down since the 30 min @ 100% extra charge (see attached image). FWIW - max discharge since then has only been down to around 50% so maybe I should try letting it drop below 20, recharging and then rechecking.

Edit: since range estimation won't be identical when calculated at different levels of charge, perhaps I should also try recharging to 100% (if the above doesn't help).
 

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jdcollins5

Member
Aug 14, 2018
760
491
Wilmington, NC
Thanks for the feedback.

Unfortunately, capacity has only gone down since the 30 min @ 100% extra charge (see attached image). FWIW - max discharge since then has only been down to around 50% so maybe I should try letting it drop below 20, recharging and then rechecking.

Edit: since range estimation won't be identical when calculated at different levels of charge, perhaps I should also try recharging to 100% (if the above doesn't help).

There have been many posts, pro and con, about discharging below 20% and charging to 100% will help recalibrate the BMS usable battery capacity and increase range.

Most of my routine driving is short trips around town. My range miles at 90% will slowly decrease. Every couple of months I take a 250 mile trip to visit grandkids. This trip will take range miles down to 10-20%. I will charge to 100% and my range miles will increase.

So it would certainly not hurt to try.
 
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