Correlation between Supercharging Habit vs Battery Health (Degradation)

[sam132]

Dear ALL

I know that this has been a HOT topic on this forum and I don't want to start another thread that discuss same topic but I wanted to post this as I can't seem to find the answer for the following:

Background:
Car: Late 2017 Tesla Model S 100D
Home: At this time, I don't have charging option in my APT and must rely on Supercharger
Charging Method: Strictly supercharging for time being (until I move to a house). Fortunately, I live very close to Supercharging station.

Knowing that home charging up to 80 ~90% is the best practice for the battery,

Question:
1) There is an ability to control the "Charge Current" on the left bottom corner of the charging screen. Mine is currently set to 72A. Is it better for the battery if I charge at lower current? If so, what is the ideal current to minimize the battery degradation?

2) We all know that car charges faster when battery is low and charging speed slows as you reach 60%+ SoC. The question is,
Should I charge more frequently when my battery is at 50%+ OR charge less frequently by getting my battery level down to 20%?
In another words, which is better for battery health? More frequent charging at lower kW/H (ie. 65) or less frequent charging at higher kW/H (ie 100+)?


All your experts' opinion will be very much appreciated.

 

[Cheburashka]

The answer to #1 is no. You cannot control the charge current at a Supercharger.

 

[ucmndd]

Given your circumstances, just charge when you need to / when it's convenient. Nothing you can control is going to substantially affect your battery one way or another.

 

[sam132]

The answer to #1 is no. You cannot control the charge current at a Supercharger.

Thank you! Before I start supercharging, I am able to go into the charging screen and set the maximum current (whether it's 50A or 60A) and then supercharge. What was surprising is that even though I set the current to 50A, the battery was still being charged at a rate of 100kW/H or higher when the battery SoC was around 20%.

 

[Cheburashka]

Thank you! Before I start supercharging, I am able to go into the charging screen and set the maximum current (whether it's 50A or 60A) and then supercharge. What was surprising is that even though I set the current to 50A, the battery was still being charged at a rate of 100kW/H or higher when the battery SoC was around 20%.

That setting is for level 1/2 AC charging, not supercharging.

 

[sam132]

That setting is for level 1/2 AC charging, not supercharging.

Ah ha!

IT makes sense. THat's why I saw rate of charge (150kW/H) even though I dropped the max current to 50A.
Thank you for the clarification!
Sam

 

[Uncle Paul]

Seems that Supercharger negative effects is determined by the total amount of current that is supplied. Slight differences between the full and tapered flooding of the cells by DC current.

 

[Rocky_H]

The horrible units in this thread are giving me a headache.
kW/hr is not a thing! Charging speed is measured just in kilowatts (kW). Amounts of energy are kilowatts multiplied by the time, so they are kilowatt hours.

There is an ability to control the "Charge Current" on the left bottom corner of the charging screen. Mine is currently set to 72A. Is it better for the battery if I charge at lower current? If so, what is the ideal current to minimize the battery degradation?

Those are amps for your home charging on a 240V AC circuit. 72 amps times 240 volts is only 17 kilowatts. That is still incredibly slow from the battery's perspective that can take well over 100 kW. So no, it doesn't make any difference what you set that for on your home charging. ALL home charging is slow charging.

2) We all know that car charges faster when battery is low and charging speed slows as you reach 60%+ SoC. The question is,
Should I charge more frequently when my battery is at 50%+ OR charge less frequently by getting my battery level down to 20%?
In another words, which is better for battery health? More frequent charging at lower kW/H (ie. 65) or less frequent charging at higher kW/H (ie 100+)?

The data on lithium ion batteries does show that smaller more frequent charging sessions is less degradation than saving it up and doing much bigger charging sessions. But really if you're not going below 20% and only going back up to 80 or 90%, you're staying in the "not very harmful" area anyway, and the differences would be pretty marginal and hard to measure I would think.

 

[sam132]

The horrible units in this thread are giving me a headache.
kW/hr is not a thing! Charging speed is measured just in kilowatts (kW). Amounts of energy are kilowatts multiplied by the time, so they are kilowatt hours.

Those are amps for your home charging on a 240V AC circuit. 72 amps times 240 volts is only 17 kilowatts. That is still incredibly slow from the battery's perspective that can take well over 100 kW. So no, it doesn't make any difference what you set that for on your home charging. ALL home charging is slow charging.


The data on lithium ion batteries does show that smaller more frequent charging sessions is less degradation than saving it up and doing much bigger charging sessions. But really if you're not going below 20% and only going back up to 80 or 90%, you're staying in the "not very harmful" area anyway, and the differences would be pretty marginal and hard to measure I would think.

 

[sam132]

Thanks, I also assumed that more frequent charging at slower charging speed (less current, less heat, less cooling) would be better for the battery. It seems that if I plan to stay within 20 ~ 80% SoC, that it really doesn't have a huge impact to the battery health. THANK YOU!!

 

[tnt1971]

There is a benefit to slower charging while not at a supercharger. The onboard charger in the car will last longer at lower amps and less heat. This is especially true for those of us that have the old, 40 amp onboard chargers.

 

[dark cloud]

Dear ALL

Knowing that home charging up to 80 ~90% is the best practice for the battery,

.

No, it is not "best practice" but it is fine. If you never need more than a 70% level than why go above that, then that would be best practice, other than to cycle/rebalance a few times a year or so. And that doesn't talk about the coolant pump and fans that seems to run much longer at SOC levels above 75% or so, car dependent, so there are other parts to think about beyond the pack. Also the statement above also doesn't indicate how low you bring the SOC down to, the higher the better.

Basically the more to the middle you can keep the battery SOC is the "best practice" as far as everything I have read (from the people whose lives have been dedicated to lithium ion battery development) 30-70% should in theory be better than 20-80%, but in real life terms all other variables being equal, having 2 identical battery samples from the centre of the bell curve, does the first degrade 6% over 4 years while the second degrades 6.5% over the same period? As Rocky pointed out who would notice the difference.

By the way who ever tracked their mileage in their ICE's over time?

The answer to #1 is no. You cannot control the charge current at a Supercharger.

Actually, a smart ass answer is yes you can. At non-urban superchargers if you strategically always wait until another car plugs in, and you take the pedestal that shares the same circuit you can supercharge at lower kW levels, but it's a crap shoot because you don't know the SOC of the other car, and of course no-one is that eccentric.

 

[dark cloud]

Another thought....

Let's say in 5 years there is someone shopping for a used model S, and he/she finds 2 identically optioned same age, same mileage, no accident used Raven's for sale, with exception that one is black and one is silver, and one owner claims they always charged at home and kept the SOC within 20-80%, and other doesn't know/didn't keep track.

I would bet the colour choice would be the bigger determining factor as to which car gets bought. I would also bet most new Tesla buyers don't even know to check the 90% range at all.

 

[tnt1971]

Another thought....

Let's say in 5 years there is someone shopping for a used model S, and he/she finds 2 identically optioned same age, same mileage, no accident used Raven's for sale, with exception that one is black and one is silver, and one owner claims they always charged at home and kept the SOC within 20-80%, and other doesn't know/didn't keep track.

I would bet the colour choice would be the bigger determining factor as to which car gets bought. I would also bet most new Tesla buyers don't even know to check the 90% range at all.

Except that I would tell a private party that my car was rarely over 70% SOC and never sat there, as well as the fact I babied my onboard charger, capping it at 32amps most of the time. I also have screenshots of every range charge, showing the degradation over the 5 or so years I have owned it (there are only about 5 of those). That might overcome the color preference.