How do you calculate Battery Degradation?

[generaltso]

Recurrent offers this service. I remember seeing some discussion about it on the forum. As I recall, some people were concerned about privacy, since you need to give them access to your vehicle‘s data.

https://www.recurrentauto.com/

People should be concerned about more than just privacy. Ford will actively lock your account if you provide Recurrent with your credentials.

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[Maquis]

So what does it mean if my display shows 100% in warm weather, and 100% in cold weather?

I don’t know the exact curve of our specific battery, but this is a typical lithium-ion:

 

[superdave80]

One of the reason for the difference between useable and actual battery capacity is give some headroom on degradation.

That isn't the reason. The reason there is a small amount of unusable battery capacity is to prevent the battery draining completely to (actual) 0%, or being charged to (actual) 100%. Both of these conditions can severely damage or shorten the life of the battery.

 

[mkhuffman]

I am interested in what @Mach-Lee thinks to add to this interesting discussion.

I have been monitoring my SoH using CarScanner and it is slowly declining. Last time I checked, it was around 95%. The first time I checked, it was 96.5%. I know many people think that value means nothing, but I am very curious where it comes from if it is meaningless. And I don't like seeing the number go down.

 

[mkhuffman]

Recurrent offers this service. I remember seeing some discussion about it on the forum. As I recall, some people were concerned about privacy, since you need to give them access to your vehicle‘s data.

https://www.recurrentauto.com/

Tronity also provides this. Tronity used my user ID and PW to get to my data, which I should have been more careful about as others have noted.

Regardless, the graph doesn't seem right to me. Does it really vary like that over time? And then it flat-lined after the cold temperatures passed and never changed again. I removed my car to unlock my Ford user account, so no new data to see what happens this winter.

 

[Maquis]

Tronity also provides this. Tronity used my user ID and PW to get to my data, which I should have been more careful about as others have noted.

Regardless, the graph doesn't seem right to me. Does it really vary like that over time? And then it flat-lined after the cold temperatures passed and never changed again. I removed my car to unlock my Ford user account, so no new data to see what happens this winter.

As far as I know, Li-Ion battery degradation isn’t reversible. Looks like crap data, IMO.

 

[OldEVGuy]

People should be concerned about more than just privacy. Ford will actively lock your account if you provide Recurrent with your credentials.

Good to know.

If you’re close to selling the car, let’s say, a month or so, will it matter if your account is locked? Recurrent makes it sound like the information they provide, can help sell it for more, as long as the battery hasn’t degraded too much. Just wondering?

 

[generaltso]

Good to know.

If you’re close to selling the car, let’s say, a month or so, will it matter if your account is locked? Recurrent makes it sound like the information they provide, can help sell it for more, as long as the battery hasn’t degraded too much. Just wondering?

In my opinion, nothing from Recurrent will translate into getting more money for your car.

 

[iankellogg]

i have a built in feb 2021 with 47k miles. SoH reads at 97%. I've done a fair number of fast charges and 100% to sub 5% trips. No one should be worried about battery health yet.

 

[Terence Murphy]

Best strategy for resale:
1. Wait until summer
2. Reset GOM
3. Drive like grandma to get range up to 350-400 miles guessed
4. Sell to sucker. Make sure they don’t know where you live

 

[breeves002]

I really don't know how we'll be able to measure/prove degradation outside warranty, but it might be interesting to dig up the actual warranty language and test procedure that (will) be used. I would bet that capacity testing for warranty claims has to be done at 'room temp' for full charge and discharged under a specific load, perhaps on a dyno.

They don't do capacity testing most likely that would be a large waste of resources for them to do because a customer complains they have low range. There is a code set when the battery gets below a capacity threshold saying the battery needs to be replaced essentially. BECM P0A7F is the "battery deteriorated" code. We see this code with Cmax Energi's with batteries that are at EOL. Generally it's due to heat because of the stupid very poor battery cooling design of the cmax. You'll also see P0B24 if a cell is going bad.

 

[Mach-Lee]

I am interested in what @Mach-Lee thinks to add to this interesting discussion.

I have been monitoring my SoH using CarScanner and it is slowly declining. Last time I checked, it was around 95%. The first time I checked, it was 96.5%. I know many people think that value means nothing, but I am very curious where it comes from if it is meaningless. And I don't like seeing the number go down.

From what I've seen, in order for that to be remotely accurate you have to charge from 10% to 100% to calibrate the BMS before reading the parameter. It is a best guess of the capacity. I'm not sure if it compensates for cold either.

 

[phidauex]

I don’t know how this LG BMS calculates state of health (SOH) but for comparable BMS’s in other vendor’s systems, the BMS looks at the drop in voltage compared to the actual charge delivered, and compares that to lookup tables of expected behavior. Unbalanced cells or modules can cause the value to drift, and the BMS needs occasional charges to 100% to recalibrate. I don’t know if the LG BMS can recalibrate at the ~96% or so that our “100%” is, but I would hope so.

Note as well that with most chemistries the initial degradation is a bit higher than the ongoing degradation. I suspect most people will see a quick drop to 97-98%, and then a more gradual reduction after that.

 

[dtbaker61]

They don't do capacity testing most likely that would be a large waste of resources for them to do because a customer complains they have low range. There is a code set when the battery gets below a capacity threshold saying the battery needs to be replaced essentially. BECM P0A7F is the "battery deteriorated" code. We see this code with Cmax Energi's with batteries that are at EOL. Generally it's due to heat because of the stupid very poor battery cooling design of the cmax. You'll also see P0B24 if a cell is going bad.

Are there sensors on every cell, or just down to parallel chunks? I.m wondering how they count effectively dead cells to calculate capacity loss.


I.d be curious to know what procedure will be used to prove or disprove claimed degradation exceeding 20%...?

It is quite difficult to do accurately with lithium packs.

 

[breeves002]

Are there sensors on every cell, or just down to parallel chunks? I.m wondering how they count effectively dead cells to calculate capacity loss.


I.d be curious to know what procedure will be used to prove or disprove claimed degradation exceeding 20%...?

It is quite difficult to do accurately with lithium packs.

Yes the voltage of every cell is closely monitored and the BMS keeps track of the capacity of every individual cell. It’s not that hard for it to calculate the capacity. It does get less accurate over time if you never charge to 100% but it still is a decent calculation.

Also the warranty is 30%+ degradation.

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