Is it beneficial to periodically charge to 100% SOC

[dk10438]

Hi,
I've seen in random threads that occasionally owners will have what appears to be premature degradation and some people will often suggest doing a "deep charge", ie deplete the battery to 5-10% and then L2 charge the battery to 100%. So my question is to optimally maintain battery health, is there any benefit or advantage to charging to 100%. Or are people doing that just to see what max battery capacity is and the occasional trip??
Dave

 

[DirtyT3sla]

I really don't think it matters at all. I've charged to 100% maybe 3 or 4 times in 13k miles and I still get 307 miles max range

 

[ckoval7]

There is some number over 90% (I think 93%, but don't quote me) that triggers the BMS to re-balance the cells. Other than that, no real benefit.

 

[ucmndd]

There is some number over 90% (I think 93%, but don't quote me) that triggers the BMS to re-balance the cells. Other than that, no real benefit.

This might have been true like 4 years ago, but it’s no longer the case. The BMS balances the cells as necessary, without any intervention, at any state of charge.

OP, charge to 100% when you need to. There is no battery health benefit to doing so occasionally. The battery is very good at taking care of itself.

 

[ran349]

Since SOC% is equal to % of rated miles, you don't have to charge to 100% to determine your full capacity. Charging to 80% or 90% will convert directly to your capacity at 100%. If you do charge to 100%, you are not supposed to let it sit long at that state, so you should plan to drive soon after charging in that case.

 

[TexasEV]

Since SOC% is equal to % of rated miles, you don't have to charge to 100% to determine your full capacity. Charging to 80% or 90% will convert directly to your capacity at 100%.

This is incorrect, because it’s not just a simple math equation. Battery SOC can’t be measured directly. It’s estimated by an algorithm that can be more or less accurate depending on how you’ve charged recently. So what the car reports as 80% range may be less than 80% of it’s actual range, for example, especially if you routinely only charge the car to 70% or less.

The only way to know the range at 100% charge is to charge to 100%. That doesn’t mean you should do it though , unless you are going on a trip and leaving soon after the 100% charge.

 

[TexasEV]

I didn't say it was a simple math equation. But that is what the algorithm is trying to do. With my car at least, 80%, 90% or whatever percent I charge to, it always converts to close to the same 100% value. Maybe that isn't true for other people, but I would like to see what others do report. I'm not talking about when the BMS calibration is way off, and a 0% to 100% charge will change the rated miles number. I'm not sure how often that really happens though.

You certainly were implying to just do the math. My point is you don’t know when the BMS calibration is off or by how much, and extrapolation from range reported at 80% charge to actual range at 100% isn’t accurate. That’s why you have to charge to 100% if you really want to know your capacity. The lower the SOC someone routinely charges to, the more likely this will happen. Search for all the reports of what range people show when they only charge to 60 or 70% because they’re obsessed with preventing battery degradation.

 

[immolated]

This might have been true like 4 years ago, but it’s no longer the case. The BMS balances the cells as necessary, without any intervention, at any state of charge.

This isn't true. Last month, I charged to 100% for the first time in about a year for a road trip. After the trip was over, I plugged in at home where I have 80% max set., but the next morning I woke up to an 85% battery. Concerned something was wrong with my charger not turning off or something, I called tesla, and they said the logs showed the BMS had re-calibrated itself overnight and adjusted the displayed SOC from 80% to 85%.

 

[NickleNiceness]

Doesn't that imply you lost range ?

 

[ucmndd]

This isn't true. Last month, I charged to 100% for the first time in about a year for a road trip. After the trip was over, I plugged in at home where I have 80% max set., but the next morning I woke up to an 85% battery. Concerned something was wrong with my charger not turning off or something, I called tesla, and they said the logs showed the BMS had re-calibrated itself overnight and adjusted the displayed SOC from 80% to 85%.

I don't think there's any correlation between what you're reporting and what ckoval7 implied. In fact, you seem to be explicitly stating that whatever "recalibration" happened occurred at 80% SoC, not 93+.

 

[TexasEV]

This isn't true. Last month, I charged to 100% for the first time in about a year for a road trip. After the trip was over, I plugged in at home where I have 80% max set., but the next morning I woke up to an 85% battery. Concerned something was wrong with my charger not turning off or something, I called tesla, and they said the logs showed the BMS had re-calibrated itself overnight and adjusted the displayed SOC from 80% to 85%.

You’re confusing battery balancing with recalibration of the estimated SOC (range).

 

[immolated]

Doesn't that imply you lost range ?

No, my car went from thinking it had 234mi remaining (80%), to 248mi remaining(85%).

I don't think there's any correlation between what you're reporting and what ckoval7 implied. In fact, you seem to be explicitly stating that whatever "recalibration" happened occurred at 80% SoC, not 93+.

No, it was getting to 100% that triggered the recalibration request next time the car slept. That was the only time in 3 years ownership that I woke up to the car being above the 80% I set the charge limit to.

 

[ucmndd]

No, it was getting to 100% that triggered the recalibration request next time the car slept. That was the only time in 3 years ownership that I woke up to the car being above the 80% I set the charge limit to.

Again, I think you’re implying causation where none exists. In fact, many people have reported changes in rated range or other calibration-like activities happening after installing 2019.16.x, which I think is a far more likely trigger than your coincidental 100% charge the day before.

I’ve noticed similar behavior twice myself so far since 2019.16, with my desired charge set to 90% but the car reporting 92% in the morning.

 

[immolated]

Again, I think you’re implying causation where none exists. In fact, many people have reported changes in rated range or other calibration-like activities happening after installing 2019.16.x, which I think is a far more likely trigger than your coincidental 100% charge the day before.

I’ve noticed similar behavior twice myself so far since 2019.16, with my desired charge set to 90% but the car reporting 92% in the morning.

I'm still on version 2018.34 (hate v9)

 

[ran349]

No, my car went from thinking it had 234mi remaining (80%), to 248mi remaining(85%).

234 mi at 80 % = 292.5 miles at 100%. 248 miles at 85% = 291.8 miles at 100%. That's basically a wash when you consider the rounding uncertainty in the numbers. That fact that your car charged to 85% doesn't mean much. I doubt it will continue doing that.

 

[Exiom]

...triggered the recalibration request next time the car slept...

Sorry to go off-topic but is the car "SLEEPING" a prerequisite to triggering recalibration?

Because I have never had the car suddenly report range that significantly differ more or less than the last time I charged but just a gradual decrease kilometre by kilometre over time and the rare few instances I charged to 100% did not have any obvious signs that something was different.

I also use logging tools like Teslafi and have my car set to always connected with no power savings of any kind, so my car actually never sleeps.

 

[TexasEV]

I also use logging tools like Teslafi and have my car set to always connected with no power savings of any kind, so my car actually never sleeps.

What a waste of electricity.

 

[immolated]

234 mi at 80 % = 292.5 miles at 100%. 248 miles at 85% = 291.8 miles at 100%. That's basically a wash when you consider the rounding uncertainty in the numbers. That fact that your car charged to 85% doesn't mean much. I doubt it will continue doing that.

That's not how it works. My car stopped charging at 80%, then calibrated at some point over night. It went from 80% to 85% with no charging (tesla rep said the logs showed this). Hence more range based on the same reference voltage. It essentially adjusted the 0 mi point of the battery.

 

[ran349]

That's not how it works. My car stopped charging at 80%, then calibrated at some point over night. It went from 80% to 85% with no charging (tesla rep said the logs showed this). Hence more range based on the same reference voltage. It essentially adjusted the 0 mi point of the battery.

So what is your 80% charge now compared to what it was before the incident you described? In other words, what is different now?

 

[ran349]

You certainly were implying to just do the math. My point is you don’t know when the BMS calibration is off or by how much, and extrapolation from range reported at 80% charge to actual range at 100% isn’t accurate. That’s why you have to charge to 100% if you really want to know your capacity. The lower the SOC someone routinely charges to, the more likely this will happen. Search for all the reports of what range people show when they only charge to 60 or 70% because they’re obsessed with preventing battery degradation.

Once the BMS determines SOC, then it does convert that to rated miles using simple math. That can be seen from Scan My Tesla data. So for people that usually charge to 80 or 90%, charging to 100% will probably not give them much different range that the projected value.