Battery SOH - bragging rights or bullshit?

[chl]

It used to be between 3-15mV but as of a month ago it's between 15-30mV.


I ran that report in January so there was no deviation to speak of, but if I notice it going over 30mV I'll probably run another one just to see what it looks like.

Yes, doubling to 30mV and approaching the threshold is concerning.

I wonder what the threshold is for Ford to do a module replacement, or do you just have to wait for the failure messages?

Sponsored

 

[electricpig]

PS: To put my numbers into perspective...

My truck is a 2023 Pro with an SR battery, manufactured in Oct 2023, bought in Jan 2024.
It has under 3500 miles on it.
I never DC charged it.
A couple times it got charged to 100% by accident after an OTA changed things, but for the first 1-1/2 years I charged to 80% at 48A max.
Now I usually charge to 90% at 32A max so I have a bit more in case of a utility outage.
It lives outdoors but I keep it plugged in to my FCSP in cold weather (below 40F).
Mostly do local driving, rarely over 45mph.
---
Always on a 12v battery NOCO GENIUS1 maintainer now since the summer of 2024 when an OTA failed.

Had a small screw in one tire that I patched successfully - other than that, no issues except with the FCSP software setup that was finicky until an update in March 2025 fixed it.

I am set up for PPOB to GENERAC transfer switch for house backup in an outage since June 2025 - but so far haven't had one. It'll be worth the $600 it cost me if it ever happens.

Did some FORscan tweaks for the headlights, chimes, etc. which improved my sense of satisfaction with the Lightning.

IMHO, I just think you need to charge to 100% and let it sit plugged in fully charged for several hours (in moderate temps) to let the ceels balance. Then run it down to around 10% as quickly as reasonable, and repeat to 100% as above. That is the method to fully rebalance and recalibrate that I have read the electrical engineer that works with Martin Meeks. Martin rebuilds Lightnings.

 

[chl]

IMHO, I just think you need to charge to 100% and let it sit plugged in fully charged for several hours (in moderate temps) to let the ceels balance. Then run it down to around 10% as quickly as reasonable, and repeat to 100% as above. That is the method to fully rebalance and recalibrate that I have read the electrical engineer that works with Martin Meeks. Martin rebuilds Lightnings.

Yea, I've heard that before.
And I have seen a couple Martin Meeks rebuild videos, but I don't recall the name of an EE who works with him or reading anything about the balancing proceedure by someone associtiated with Meeks - got a link?

An AI search result may tell you to do that same thing, charge to 100% once a month, etc.
I don't think it is absolutely necessary but it is not going to hurt much.

Ford recommends charging to 90% for daily use, 100% only when long trips are planned.

Ford has not revealed all the details of their cell balancing program, but since they recommend 90% one would think/hope that would be adequate for balancing and battery health.

Ford warrants the battery for 8 years and 100k miles, so they have skin in the game of keeping the battery healthy.

If the charging to 100% etc process once a month was "necessary" for battery longevity, I'd expect Ford to say so and recommend it.

We all know frequent charging to 100% will cause degrading of the battery faster than not.
But once a month to 100% is probably not going to do any measurable harm to the battery, if you want to do it.

It may help re-calibrate the guess-o-meter, but that is not a concern of mine, I pretty much ignore the range estimate.

If the BMS really needs re-calibration/reset, because of drift or whatever, there should be tell-tales signs.

There are several methods I have read about for reset/recalibration/rebalancing.

----
NOTE: I have not verified these methods so attempt them at your own risk.

One methods says, first charge to 100% and let it sit there for some period of time still plugged in, a couple of hours at least. Then you discharge down to a safe low level like 20% and let it sit for several hours - that's a lot of driving, more than I usually do. Then you charge back up to 100%.

Another method is to take it down to 10% and let it sit there for some time with the truck ON in ACC mode, then charge to 100% and drive around a to let the BMS relearn the battery level.

The HVBMS might also be reset using an OBD tool and FORscan or FDRS according to internet sources.

There is also a battery pack re-balancing procedure accessible in FORscan or FDRS according to internet sources.

NOTE: I have not verified these methods so attempt them at your own risk.
----

But I think that since cell balancing occurs during charging, and takes time (because the discharge current of the stronger cells through resistance to match the weaker cells has to be limited), a slow charge to 80% or 90% ought to be good enough to achieve good balancing results in theory.

----

MY RESULTS:

So far, I see barely any delta in my battery from CarScanner readings.

For the first 1-1/2 years, I only charged my Pro SR at 48A max and only to 80%.
I have only charged to 100% by accident one or two times since I got the truck in Jan 2024.
So far, I never needed or did any DC fast charging.

While I do have low mileage (under 3500) and have just under 10 full charge cycles, if not going to 100% once a month was an big issue, I think I would see some cell imbalances by now.
But I don't.

I recently lowered my max amps to 32A which is adequate to charge to what I need within the 4 hour off peak rate time, 1AM to 5AM, so my charging is even 'slower' now.

Higher current means higher heat losses in wires, AC-DC conversion, etc. due to I^2xR (current squared times resistance) so to save a few pennies over the long haul, I reduce the max current.

---

Now, IF I saw a greater than 30mV delta, I'd probably try on of the methods above.

(I am also an electrical engineer with a masters degree and a JD, and I have worked in the patent field since 1985.)

 

[mr.Magoo]

Higher current means higher heat losses in wires, AC-DC conversion, etc. due to I^2xR (current squared times resistance) so to save a few pennies over the long haul, I reduce the max current.

Except that you're not saving anything, quite the opposite.
Didn't we just cover this ?

Besides, my great grandmother's second cousin was a pet sitter for Edisons cat "Watts" so I know a thing or two about electricity as well.

 

[electricpig]

Yea, I've heard that before.
And I have seen a couple Martin Meeks rebuild videos, but I don't recall the name of an EE who works with him or reading anything about the balancing proceedure by someone associtiated with Meeks - got a link?

An AI search result may tell you to do that same thing, charge to 100% once a month, etc.
I don't think it is absolutely necessary but it is not going to hurt much.

Ford recommends charging to 90% for daily use, 100% only when long trips are planned.

Ford has not revealed all the details of their cell balancing program, but since they recommend 90% one would think/hope that would be adequate for balancing and battery health.

Ford warrants the battery for 8 years and 100k miles, so they have skin in the game of keeping the battery healthy.

If the charging to 100% etc process once a month was "necessary" for battery longevity, I'd expect Ford to say so and recommend it.

We all know frequent charging to 100% will cause degrading of the battery faster than not.
But once a month to 100% is probably not going to do any measurable harm to the battery, if you want to do it.

It may help re-calibrate the guess-o-meter, but that is not a concern of mine, I pretty much ignore the range estimate.

If the BMS really needs re-calibration/reset, because of drift or whatever, there should be tell-tales signs.

There are several methods I have read about for reset/recalibration/rebalancing.

----
NOTE: I have not verified these methods so attempt them at your own risk.

One methods says, first charge to 100% and let it sit there for some period of time still plugged in, a couple of hours at least. Then you discharge down to a safe low level like 20% and let it sit for several hours - that's a lot of driving, more than I usually do. Then you charge back up to 100%.

Another method is to take it down to 10% and let it sit there for some time with the truck ON in ACC mode, then charge to 100% and drive around a to let the BMS relearn the battery level.

The HVBMS might also be reset using an OBD tool and FORscan or FDRS according to internet sources.

There is also a battery pack re-balancing procedure accessible in FORscan or FDRS according to internet sources.

NOTE: I have not verified these methods so attempt them at your own risk.
----

But I think that since cell balancing occurs during charging, and takes time (because the discharge current of the stronger cells through resistance to match the weaker cells has to be limited), a slow charge to 80% or 90% ought to be good enough to achieve good balancing results in theory.

----

MY RESULTS:

So far, I see barely any delta in my battery from CarScanner readings.

For the first 1-1/2 years, I only charged my Pro SR at 48A max and only to 80%.
I have only charged to 100% by accident one or two times since I got the truck in Jan 2024.
So far, I never needed or did any DC fast charging.

While I do have low mileage (under 3500) and have just under 10 full charge cycles, if not going to 100% once a month was an big issue, I think I would see some cell imbalances by now.
But I don't.

I recently lowered my max amps to 32A which is adequate to charge to what I need within the 4 hour off peak rate time, 1AM to 5AM, so my charging is even 'slower' now.

Higher current means higher heat losses in wires, AC-DC conversion, etc. due to I^2xR (current squared times resistance) so to save a few pennies over the long haul, I reduce the max current.

---

Now, IF I saw a greater than 30mV delta, I'd probably try on of the methods above.

(I am also an electrical engineer with a masters degree and a JD, and I have worked in the patent field since 1985.)

It was just n a podcast they were doing that I happened to see. They said the wires to balance the cells were absolutely tiny and could carry very little energy, therefore it took several hours of "resting" after reading 100% to balance cells at a mint. So he was saying to let it sit at 100 for 4-6 hours at least before driving, but don't let it sit at 100 for days especially in the heat of summer. He also said he was charging his to 100 at least once a month, but he also drives allot, so that could be a factor in frequency. In another instance I though he said he has 145K on his SR Lightning, but I'm not certain I heard it correctly. Believe it or not, doesn't matter to me. Just spreading what I was lucky enough to tune into, and the reasoning behind it.

 

[chl]

Except that you're not saving anything, quite the opposite.
Didn't we just cover this ?

Besides, my great grandmother's second cousin was a pet sitter for Edisons cat "Watts" so I know a thing or two about electricity as well.

The wasted/lost energy due to resistance is in the wiring and the AC-DC converter as well as internally to the battery.

The quantity of lost energy is dependent on current and goes up with the square of the current and the length of time.

It is why the utilities step up the voltage on transmission lines so they can deliver the same energy with less loss due to transmission wire resistance.

If we do the math, current x current x resistance = power; x time = energy lost so assuming 1 ohm resistance and 1 hour time, to make the math easier:

1 ohm x 80 amps x 80amps x 1 hour = 6.4kWh
1 ohm x 32 amps x 32 amps x 1 hour = 1.024kWh

That should make it clear that considerably more energy is lost to resistance at 80 amp compared with 32 amps.

Power can also be expressed as current x voltage, and using the EVSE L2 level of 240 volts:

240 volts x 32 amps = 7.68kW

The energy is the power x time, so in 1 hour that is 1h x 7.68kW = 7.68kWh

But we have to subtract the losses due to 1 ohm in one hour to get the energy transferred to your truck at 32 amps:

7.68kWh - 1.024kWh = 6.656kWh transferred to the truck in 1 hour at 32A.

At the higher current, 240 volts x 80 amps = 19.2kW is the power and in 1 hour 19.2kWh is the energy produced.

Subtracting the loss due to 1 ohm resistance, in one hour: 19.2kWh - 6.4kWh = 12.8kWh is transferred to the truck.

12.8kWh/6.656kWh = 1.92 which means the energy is transferred about twice as fast at 80A than at 32A, so it takes about twice as long to transfer the same amount of energy.

So, suppose we want to add about 12.8kWh to the truck.

It takes about 1 hour at 80 amps with 6.4kWh lost to heat using our values.

At 32 amps it takes about 2 hours with 2 x 1.024kW = 2.048kWh lost to heat.

So the energy lost due to resistance is about significantly larger at 80 amps than at 32 amps.

We could get exact and plug in the resistance per foot of the wire etc. if we wanted to - I may at some point.

I have about 75ft run from the service panel to the FCSP.
You may have a lot less so your wire resistance losses could be a lot less, I don't know.

For any given session it may only be a small amount of cost in wasted energy.

Currently, I pay about 15 cents per kwh, but over time it adds up - and rates will probably rise due to data centers' demand and fuel costs.

Bottom line if the additional time spent charging is important and worth the additional kWh cost, then use the higher current.

 

[chl]

It was just n a podcast they were doing that I happened to see. They said the wires to balance the cells were absolutely tiny and could carry very little energy, therefore it took several hours of "resting" after reading 100% to balance cells at a mint. So he was saying to let it sit at 100 for 4-6 hours at least before driving, but don't let it sit at 100 for days especially in the heat of summer. He also said he was charging his to 100 at least once a month, but he also drives allot, so that could be a factor in frequency. In another instance I though he said he has 145K on his SR Lightning, but I'm not certain I heard it correctly. Believe it or not, doesn't matter to me. Just spreading what I was lucky enough to tune into, and the reasoning behind it.

Thanks for the reply, interesting.

Yes, I'm not saying it doesn't work, just that I don't think it is absolutely necessary.

The difference between 80%, 90% and 100% charging for balancing effects may be minimal, who knows?

And besides, we have a buffer of battery anyway so we never REALLY charge to 100% because of it.

So, I'm not going to go out of my way to do the charge to 100% every month routine...unless I see some kind of delta.

 

[potato]

If we do the math, current x current x resistance = power; x time = energy lost so assuming 1 ohm resistance and 1 hour time, to make the math easier:

1 ohm x 80 amps x 80amps x 1 hour = 6.4kWh
1 ohm x 32 amps x 32 amps x 1 hour = 1.024kWh

I feel like if you are dissipating 1 kW (or 6 kW!!!) as heat in your wires, you have some bigger problems somewhere lol. (That 1 ohm number must be way too high.)

The principle is sound of course. Higher current = higher power loss. BUT there is also fixed overhead to run pumps, fans etc. in the truck during charging. So higher current shortens the overall time therefore the overall loss due to the fixed overhead. There's probably some optimum rate where the two lines would cross on a graph.

 

[chl]

I feel like if you are dissipating 1 kW (or 6 kW!!!) as heat in your wires, you have some bigger problems somewhere lol. (That 1 ohm number must be way too high.)

The principle is sound of course. Higher current = higher power loss. BUT there is also fixed overhead to run pumps, fans etc. in the truck during charging. So higher current shortens the overall time therefore the overall loss due to the fixed overhead. There's probably some optimum rate where the two lines would cross on a graph.

Yes, true, I just used 1 ohm for math convenience, the #6awg wire used for 80A install has a lot less resistance than 1 ohm.

I think 100 feet has a resistance of somewhere around 0.05 ohms, two hots means twice that around 1/10th of an ohm.

If you use smaller diameter wire for the install for 48A or 32A, you save money on the wire cost upfront, but the smaller wire has a higher resistance so at the lower current more would be wasted that with larger diameter wire.

Always trade offs.

In a residential single charger install they maybe small differences, in an industrial setting those things have to be taken into account.

And I agree if time is most important, use a faster rate/higher current.

I was just taking issue with the idea that higher current has no effect on the energy wasted.

There are other reasons to use a lower current besides the wasted energy.

The heat inside the FCSP at higher currents (80A) has been an issue for some - even if torqued correctly, the heating and cooling effects over time cause expanding and contracting can loosen connections, and the FCSP does not have a fan or other active cooling mechanism (it will slow down the charge speed if things get too hot though).

Less stress on the breaker, the charge port, the battery, etc., too.

The longer charge time at a lower current gives the truck more time to charge the 12v battery, and more time for the passive balancing the HVB (in theory).

Not sure what the fixed over head number is, but yes there is some for sure.

I do see a very small difference in energy used vs added to the battery between 48A and 32A when I have a longer charge time. Usually I do small percentage charges though rarely even 20% (70 to 90), and I have the SR 98kWh battery.

Anyway, little things add up over time.

 

[mr.Magoo]

I was just taking issue with the idea that higher current has no effect on the energy wasted.

No one said that, ever !

The only thing we've said is that the cost (in energy consumption) to keep the truck alive longer (by charging with a lower current) outweighs any gains from reduced losses in cabling, etc.

If you chose to charge with a lower current, that's your choice, and you have your reasons that are as good as any...

But people are not saving money by charging slower, so it would be incorrect to tell them so.

 

[electricpig]

Thanks for the reply, interesting.

Yes, I'm not saying it doesn't work, just that I don't think it is absolutely necessary.

The difference between 80%, 90% and 100% charging for balancing effects may be minimal, who knows?

And besides, we have a buffer of battery anyway so we never REALLY charge to 100% because of it.
I personally don't charge to 100% monthly w
So, I'm not going to go out of my way to do the charge to 100% every month routine...unless I see some kind of delta.

Thanks for the reply, interesting.

Yes, I'm not saying it doesn't work, just that I don't think it is absolutely necessary.

The difference between 80%, 90% and 100% charging for balancing effects may be minimal, who knows?

And besides, we have a buffer of battery anyway so we never REALLY charge to 100% because of it.

So, I'm not going to go out of my way to do the charge to 100% every month routine...unless I see some kind of delta.

FWIW, I don't charge to 100% unless I'm going on a trip outside my usual sphere. Example, a.friend that lives about 80 to 90 miles away, family that is 100 plus miles, etc. I want to be sure to use the extra charge above the 80% I typically charge to. Really, I have probably fully followed their criteria only a few times.

However I was responding to the person that appears to be having balancing issues. Their responses.suggested to me that they had never changed to 100% for balancing. So for that person, it seems prudent to give it a go to see if it improves their situation, or flushes out another problem.

 

[chl]

No one said that, ever !
...
But people are not saving money by charging slower, so it would be incorrect to tell them so.

Huh? Yes they are!

If they charge with a lower current they are wasting less kWh to wire resistance, and that is what the utility charges for.

Lower current, less energy wasted to wire resistance.

It may be a small number of kWh per charge, but it adds up.

I have a 75ft run, so 150feet total of 6AWG with about 0.04 ohms per 100 feet, so 0.06 ohms total.

I did the numbers for my wiring at 80A vs 32A as an example.

---
To add about 10kWh to the battery:

At 80A it takes about .52h (31 minutes) if there were no losses due to the wire resistance.
80A x 80A x 0.06 ohms x 1 hour = 384 Wh energy lost in 1 hour
But in 0.52 hours x 384W = 199.7Wh is lost due to wire resistance
--
If I use a 32A charge current it would take about 1.3h if there were not wire resistance losses.
32A x 32A x 0.06 ohms x 1 hour = 61.44 Wh energy lost in 1 hour
In 1.3 hours x 61.44W = 80Wh lost due to wire resistance
--
The 32A charge wastes less energy than the 80A charge for adding about the same kWh to the truck battery.

Numbers don't lie.

And the difference in energy per hour wasted is about a factor of six: 384/61.44.

So even though it takes longer to add energy to the battery, it is more energy efficient to use a lower current.

The utility charges for the energy you are using whether you add it to the truck or waste it.
The less you waste, the less you pay.

---
Or put another way, it actually uses more energy at 80A than at 32A to add a kWh to the battery, and you pay for it.

Like I said, it may be a small amount of cost per charge, but over time it adds up.

Maybe time is more important to the owner than cost, then fine, use a higher current.
---
Due to wire resistance in my example:

In one hour at 80A x 24V (19.2kW), 18.82kWh is added to the battery.
For every hour at 32A x 240V (7.68kW), 7.62kWh is added to the battery.

Wasted energy costs money.

Hope that makes more sense seeing the numbers?

 

[chl]

FWIW, I don't charge to 100% unless I'm going on a trip outside my usual sphere. Example, a.friend that lives about 80 to 90 miles away, family that is 100 plus miles, etc. I want to be sure to use the extra charge above the 80% I typically charge to. Really, I have probably fully followed their criteria only a few times.

However I was responding to the person that appears to be having balancing issues. Their responses.suggested to me that they had never changed to 100% for balancing. So for that person, it seems prudent to give it a go to see if it improves their situation, or flushes out another problem.

Yes, I agree, it would be worth a try.

If there is a bad cell or two, it won't help/fix that issue.
But if there was a lot of BMS 'drift' causing the delta, then it might.

In the Leaf forum over the years it has been an issue and results were mixed.
With the Leaf, to see a balance improvement, the process of up and down between 100% and 10% had to be done three times with long pauses (5 hours or better overnight) in between!

But what people found out was a large delta was generally not fixable this way and indicated a bad cell or two. With the Leaf, there were people who would replace down to the cell pair level, quite a task!

 

[mr.Magoo]

Huh? Yes they are!

To add about 10kWh to the battery:

At 80A it takes about .52h (31 minutes) if there were no losses due to the wire resistance.
80A x 80A x 0.06 ohms x 1 hour = 384 Wh energy lost in 1 hour
But in 0.52 hours x 384W = 199.7Wh is lost due to wire resistance
--
If I use a 32A charge current it would take about 1.3h if there were not wire resistance losses.
32A x 32A x 0.06 ohms x 1 hour = 61.44 Wh energy lost in 1 hour
In 1.3 hours x 61.44W = 80Wh lost due to wire resistance


Hope that makes more sense seeing the numbers?

I have to say it's interesting that you're so hyper focused on energy losses in the cable (which I'm not arguing with by the way, yes, they're real, yes, it's a factor, yes it costs money), yet you fail to realize the energy "losses" in the truck due to heating/cooling of the battery, pumps, keeping electronics alive, charging your 12V battery, etc.
It's a bit like saying you're letting your ICE car idle through the night because cold starts are so inefficient.

In your equation the delta between the two scenarios is 120W, so as long as the truck is using less than 120w to keep things alive you'd be correct that it is a net gain by charging slower, but the truck isn't using less than that, it's using a lot more, resulting in a net loss - which I've shown here:
https://www.f150lightningforum.com/...nitor-the-j1772-negotiation.34786/post-655408

Additionally, with your logic, L1 charing would be the best thing for efficiency since there's hardly any loss at all, yet it's been talked about a million times that it isn't all that great at all.

 

[chl]

I have to say it's interesting that you're so hyper focused on energy losses in the cable (which I'm not arguing with by the way, yes, they're real, yes, it's a factor, yes it costs money), yet you fail to realize the energy "losses" in the truck due to heating/cooling of the battery, pumps, keeping electronics alive, charging your 12V battery, etc.
It's a bit like saying you're letting your ICE car idle through the night because cold starts are so inefficient.

In your equation the delta between the two scenarios is 120W, so as long as the truck is using less than 120w to keep things alive you'd be correct that it is a net gain by charging slower, but the truck isn't using less than that, it's using a lot more, resulting in a net loss - which I've shown here:
https://www.f150lightningforum.com/...nitor-the-j1772-negotiation.34786/post-655408

Additionally, with your logic, L1 charing would be the best thing for efficiency since there's hardly any loss at all, yet it's been talked about a million times that it isn't all that great at all.

Incandescent light bulb is only 5% or so efficient at producing light - 95% goes to producing heat, so unless you are operating an 'Esay Bake Oven' using an incandescent bulb is wasting energy, and you pay the utility company for it.

In cold weather, when your truck is plugged into an EVSE, if needed, the system will draw energy from the utility through your EVSE and not from the battery just for battery warming.

But that is not wasted energy.

Whether you charge at L2 at 80A or 32A, the amount of energy used by the heater will be the same.

Unless you are preconditioning the truck for a departure, just maintaining the battery temp uses 1-2kW from what I have read.

So 1-2kW will be subtracted from the available power for charging whether charging at 32A or 80A.

With L1 charging when it's cold and the battery needs to be heated, the problem is it doesn't provide enough power, barely enough to just run the heater, at best 120V x 15A = 1.8kW.
NOTE: assuming a 120A 15A circuit.

If you run the numbers subtracting 2kw from the available power for the 32A L2, then
(240V x 32A) - 2kW = 5.68kW

To add 10kWh then would take: 10k/5.68k=1.8hours
In 1.8 hours, the wire energy losses would be 61.44 x 1.8 = 111Wh

For 80A and running the heater the available power for the battery would be
(240V x 80A) - 2kW = 17.2kW

To add 10kWh then would take: 10k/17.2k=0.58hours
In .58 hours, the wire energy losses would be 384 x 0.58 = 223Wh

So the 32A rate, even subtracting the energy needed for running the battery, would still be more efficient than the 80A rate.

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