SOH is not battery capacity

[Zprime29]

But I think no matter what the scanner says for SOH, we should do the math ourselves and use the 131kWh ER usable energy as the 100% point for SOC and SOH.

If our full charge energy is 131kWh, then our SOC is 100% and our SOH is 100% for the purposes of warranty.

This right here is my opinion as well.

I see a lot of posts that put a lot of faith in SOH and I have a very vague recollection of being told by my service advisor that Ford uses the reported SOH for warranty purposes. There are clearly more factors at play in computing the SOH for the lightning than just useable capacity. We should stop using it as such until we have confirmation on the source of its inputs.

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[RickLightning]

What's interesting, which I have mentioned before, is that there are a huge number of Lightnings displaying 100% SOH, while Mach-Es don't have the same numbers, they fall.

My 2022 Lightning, purchased in May 2023 with under 500 miles on it, and driven about 23,000 miles, has a 100% SOH.

My 2022 Mach-E, purchased in May 2022, no miles on it, and driven close to 38,000 miles, has a 94% SOH.

Yes, different battery manufacturers, cells, packets, blah, blah.

I'd also point out that checking SOH at 102F is not the same as 77F.
And, the SOC DISPLAYED is 100%, when the SOC is around 95.5%, exactly as it should be.

 

[Free Charging]

Wish that the cell level health wasn't locked behind an FDRS subscription, or that the fee to access that data were much less. @Ford Motor Company

 

[chl]

This right here is my opinion as well.

I see a lot of posts that put a lot of faith in SOH and I have a very vague recollection of being told by my service advisor that Ford uses the reported SOH for warranty purposes. There are clearly more factors at play in computing the SOH for the lightning than just useable capacity. We should stop using it as such until we have confirmation on the source of its inputs.

Ford probably uses FDRS for battery analysis.

So I know there have been battery failures and replacement of modules, but have there been any warranty claims for prematurely falling below 70% other than that?

Have to look that up...none reported yet, but 8 years is a ways off.
Probably some owners have reached 100k miles...here's one.

Based on the 105mi estimated range, 2.2 mi/kWh and 54 percent SOC on the dash display, and assume a basic Pro with the 98kWh SR battery, this guy's battery is at 90% or so SOH at 100k miles.

105mi / 2.2mi/kWh = 47.72kWh
47.72kWh / 54% = 88.4kWh at 100% charge
88.4kWh / 98kWh x 100% = 90.2%

 

[Zprime29]

What's interesting, which I have mentioned before, is that there are a huge number of Lightnings displaying 100% SOH, while Mach-Es don't have the same numbers, they fall.

My 2022 Lightning, purchased in May 2023 with under 500 miles on it, and driven about 23,000 miles, has a 100% SOH.

My 2022 Mach-E, purchased in May 2022, no miles on it, and driven close to 38,000 miles, has a 94% SOH.

Yes, different battery manufacturers, cells, packets, blah, blah.

I'd also point out that checking SOH at 102F is not the same as 77F.
And, the SOC DISPLAYED is 100%, when the SOC is around 95.5%, exactly as it should be.

If I had to guess, the SOH is taking into account the battery temps that it is exposed to. I haven't been paying super close attention to where people are located when they share their SOH, I'll try to note that going forward. MickeyAO noted before he left that temps over 114F (I think) where one of the top 3 factors in cell degradation when they tested. I can guarantee my truck see's that every summer baking in a parking lot with full sun. I suspect that is contributing to my SOH being a bit lower than folk who live up north.

The thread I referenced that has a 100% display SOC was closer to ideal temps:

Voltage and actual SOC pretty much spot on, but 3 kWh less useable energy and I had a higher SOH reported. I won't be able to test in that temp range again until Oct or Nov.

 

[ctuan13]

Here's a couple different 100% charges I captured at different temperatures. All end up at the same voltage. We see the usual lower useable energy at the lower temps, but even when I was near ideal in the 70s I didn't get all the way to 131 kWh. That's why I was surprised when it got there this most recent time. As far as I know, temps above 70s are not supposed to increase capacity.

The fact that my SOH has not gone up means that it is not solely tied to useable capacity.

@astrand1 the first link makes a direct association.

I see similar statements and concerns about SOH very frequently. I only posted a few links, but there are dozens if one searches. If you want to chalk it up to me being bitter about a lower SOH than most, sure there's likely some truth to it. I mainly wanted to provide evidence I can link to when I see someone make the claim.

Thorough analysis, but you're still comparing the wrong metric. Usable Energy, indicated as "Energy(kWh)" is not the same as "[BECM] Capacity" measured in Amp hours. The BECM isn't using the "Energy(kWh)" figure to calculate SOH, but rather the "[BECM] Capacity" value.

 

[Zprime29]

Thorough analysis, but you're still comparing the wrong metric. Usable Energy, indicated as "Energy(kWh)" is not the same as "[BECM] Capacity" measured in Amp hours. The BECM isn't using the "Energy(kWh)" figure to calculate SOH, but rather the "[BECM] Capacity" value.

Wouldn't Ah * Volt = useable capacity? If the voltage is the same, but the Ah is 5% lower, then how is the useable capacity still 100%? Clearly I'm still not understanding something.

EDIT: Also, is your assertion based on anecdotal evidence or has Ford confirmed it somewhere?

 

[Grease Lightning]

Accidentally charged to 100% after recall updates erased my charge locations. I took the opportunity to check in on my battery health. 131kWh useable capacity (which I haven't seen in a while) and 95.5% SOH. Folks, I hope this convinces you to stop equating SOH to battery capacity.

For those curious, I'm at 63k miles and live in a hot climate. I DCFC 3-4 times a year and have only been under 20% SOC a handful of times (lowest I've been is 13%). I'm not worried one iota about this battery.

I think most people take the SOH as, the BMS giving us a percentage representation of the total battery capacity, including buffers. It has long been suspected that Ford designed the BMS to maximize usable capacity and allow the buffer to diminish over time to continue to give the user the 131 kWh they had at the start for say an ER battery. This practice helps ensure Ford had less chance of warranty claims for the 70% of capacity over the years or mileage required under law.

So just cause one is able to charge to 131 kWh, does not take away from from that thought. Interestingly, the post actually adds to their belief as the full battery SOC is 95.55% and the SOH is 95.5….oddly the same…….

 

[RickLightning]

SoH x battery size should equal available energy at 77 degree battery temp. That said, ENERGY is all that matters to me.

 

[Zprime29]

I think most people take the SOH as, the BMS giving us a percentage representation of the total battery capacity, including buffers. It has long been suspected that Ford designed the BMS to maximize usable capacity and allow the buffer to diminish over time to continue to give the user the 131 kWh they had at the start for say an ER battery. This practice helps ensure Ford had less chance of warranty claims for the 70% of capacity over the years or mileage required under law.

So just cause one is able to charge to 131 kWh, does not take away from from that thought. Interestingly, the post actually adds to their belief as the full battery SOC is 95.55% and the SOH is 95.5….oddly the same…….

That's a dangerous thing to do, reducing that buffer to maintain useable capacity means we inch closer to 100% actual and potentially overcharging. I have my doubts that Ford would allow that and my data indicates the opposite. 95.5% actual has not changed over the past year when I hit 100% displayed. Yet my SOH has declined...that should rule out the theory that Ford is decreasing the buffer.

SoH x battery size should equal available energy at 77 degree battery temp. That said, ENERGY is all that matters to me.

That's kinda the point I was trying to make, I see a lot of people essentially use SOH as a proxy to degradation in overall useable energy. I'm of a similar mindset to you, if I can still charge and get 131kWh useable then I don't really care what the SOH says. I thought it might be useful to convince others to not rely on the SOH as well.

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