Tracking the HVB State of Health - how much decline is normal?

[mkhuffman]

One of Ford's patents says the following about how they *might* be calculating SOH, but it's not the only model, and we don't know what the coefficients might be in the representation they include here. Note that I haven't dug into the patent to check every little detail.


The patent goes on to say...

Equations 6 and 7 are as follows:

If this patent is relevant to the Mustang, Ford is giving iteslf a lot of space to determine the SOH based on several different scenarios, including driver aggressiveness.


Link to the patent (PDF):
https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/10569660

Very interesting. That seems to explain why SoH could be lower than maximum battery capacity, but not higher. The SoH of my battery is slightly lower than what I calculate at 100% SoCD. Maybe it is all the WOTs!

 

[SpaceEVDriver]

Very interesting. That seems to explain why SoH could be lower than maximum battery capacity, but not higher. The SoH of my battery is slightly lower than what I calculate at 100% SoCD. Maybe it is all the WOTs!

I think that may be. They seem to have both a past and predicted driving behavior as part of their estimate for SOH.
I have a few WOTs, but not many.
I'm down to 96.5% after just over 20,000 miles.

 

[dtbaker61]

I'm at 93%.

40k miles
DCFC at least 4 times a week
Charge to 100% at least twice a week

I've said this before, all the research I've read says that age+not driving the car is worse for the battery than DCFC, 100% charges and charge cycles. Of course they all wear on the battery, but your better bang for buck is to drive it, charge it, do what it's designed to do and stop worrying about it.

Does anyone know exactly how the HVSoH number is derived?

There have to be some approximations and extrapolations to account for temperature, regen, and never really going from 'full' to 'empty' voltages under steady state output and conditions required for accurate energy capacity measurement.

It seems to me that this number is likely to be not much more accurate than the GOM range estimator....

 

[DevSecOps]

Does anyone know exactly how the HVSoH number is derived?

There have to be some approximations and extrapolations to account for temperature, regen, and never really going from 'full' to 'empty' voltages under steady state output and conditions required for accurate energy capacity measurement.

It seems to me that this number is likely to be not much more accurate than the GOM range estimator....

I've never seen a post with a definitive answer to how it's calculated. I agree that it's probably wildly inaccurate, or at least inconsistent which is why every time I've commented on it I've said to just drive the damn car and stop worrying about it.

 

[dtbaker61]

I've never seen a post with a definitive answer to how it's calculated. I agree that it's probably wildly inaccurate, or at least inconsistent which is why every time I've commented on it I've said to just drive the damn car and stop worrying about it.

I agree. My only concern is 8 years or 100,000 miles from now whether or not that number is what Ford uses to determine if you have a valid warranty claim or not

 

[DevSecOps]

I agree. My only concern is 8 years or 100,000 miles from now whether or not that number is what Ford uses to determine if you have a valid warranty claim or not

I really doubt that. Ford has tools, some of which are in FDRS to analyze the battery cells. I am sure that for warranty claims they have to do further diagnostic testing.

All that being said, I don't think I've ever seen a warranty replacement of an EV battery solely for SOH. Every single warranty replacement was due to a recall, damage etc. I'm not saying there haven't been any, but I've yet to see one. If they do happen it's either suppressed by the media (wouldn't surprise me one bit) or they just don't get much attention.

 

[kodiakng]

Does anyone know exactly how the HVSoH number is derived?

There have to be some approximations and extrapolations to account for temperature, regen, and never really going from 'full' to 'empty' voltages under steady state output and conditions required for accurate energy capacity measurement.

It seems to me that this number is likely to be not much more accurate than the GOM range estimator....

I've never seen a post with a definitive answer to how it's calculated. I agree that it's probably wildly inaccurate, or at least inconsistent which is why every time I've commented on it I've said to just drive the damn car and stop worrying about it.

while indicative but not definitive, @SpaceEVDriver posted a link to ford's patent for Systems and Methods for Battery State-of-Health Monitoring. filed in 2016, issued in 2020.

 

[DevSecOps]

while indicative but not definitive, @SpaceEVDriver posted a link to ford's patent for Systems and Methods for Battery State-of-Health Monitoring. filed in 2016, issued in 2020.

Yeah, but who knows if they use that. That's why I specifically said, definitive. 95% of patents filed fail to be used or issued. We can speculate all we want, but that doesn't help anyone. Until someone gets inside information or Ford comes out and says "this is what we do" we won't know.

 

[kodiakng]

Yeah, but who knows if they use that. That's why I specifically said, definitive. 95% of patents filed fail to be used or issued. We can speculate all we want, but that doesn't help anyone. Until someone gets inside information or Ford comes out and says "this is what we do" we won't know.

but you'll argue about it without definitive answers for ages.

when the available information is between "a patent ford filed for and was issued" and "waving rubber chickens in the air" i'll usually side with the patent. but hey, let us all know when you get your definitive answer.

 

[DevSecOps]

but you'll argue about it without definitive answers for ages.

when the available information is between "a patent ford filed for and was issued" and "waving rubber chickens in the air" i'll usually side with the patent. but hey, let us all know when you get your definitive answer.

I have never once claimed to know how they calculate SOH or argued about how they calculate it. So, when someone asks me, by quoting my post, if I know how it's done I answered with no, because there's nothing definitive posted about it.

You can speculate all you want but the fact is that 95% of patents don't get used. Could it be that this patent is used, sure it could be, but I'm not going to say that it's factual. An opinion, guess or suspicion is not fact.

If you think I waive rubber chickens in the air, there's an ignore button you can use.

 

[kodiakng]

I have never once claimed to know how they calculate SOH or argued about how they calculate it. So, when someone asks me, by quoting my post, if I know how it's done I answered with no, because there's nothing definitive posted about it.

You can speculate all you want but the fact is that 95% of patents don't get used. Could it be that this patent is used, sure it could be, but I'm not going to say that it's factual. An opinion, guess or suspicion is not fact.

If you think I waive rubber chickens in the air, there's an ignore button you can use.

LOL i noted it was "indicative not definitive" in my first response and nothing else. then you stamped your feet on the "definitive" end of your obsession and won't let it go.

you're just amazing.

EDIT: and then you delete all your comments in this set of posts to remove all evidence. amazing.
EDIT 2: double , i've been blocked.

 

[DevSecOps]

EDIT: and then you delete all your comments in this set of posts to remove all evidence. amazing.

Nothing is deleted, I just prevented you from seeing anything of mine, past, present or future.

 

[cbcasas]

LOL i noted it was "indicative not definitive" in my first response and nothing else. then you stamped your feet on the "definitive" end of your obsession and won't let it go.

you're just amazing.

EDIT: and then you delete all your comments in this set of posts to remove all evidence. amazing.
EDIT 2: double , i've been blocked.

He blocks everyone that calls him out. Big ego

 

[tuminatr]

So just turned 28k miles 94.5% SOH

• Daily % charge setting
  • 90% at home
• How often you L2 charge
  • Usually once per week
• How often you DC charge
  • A bunch maybe 50 to 60 times
• Does the car sit at high SoC >80%
  • Yes it's not driven daily
• How low do you go before recharging
  • Below 40% it gets charged. It's been run to 0% twice on road trips
• How often do you charge to 100%
  • Before and when on road trips maybe 20 times

 

[phidauex]

94.5% at 20k miles here, '21 Premium ER AWD.

I don't DCFC often, mostly charging at home, but the car hasn't been garaged for most of its life so it has seen a lot of extreme temps, high and low. It has also been a while since I've been to 100% SOC so my value could use a calibration.

Current mileage estimate is 242mi at 90%, or 269 miles equivalent. And that is with a bike rack on the hitch, winter tires (just changed them last weekend but haven't driven much), and moderate highway driving (65-75mph) in nice weather (55F to 75F). I'm satisfied.

That said, if this rate of change keeps up I could be at 72% at 100k miles, which isn't great. I'd rather be well above the 70% level, or just below it so I can cash in the warranty! Hopefully the rate of change isn't constant.

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