Any benefit to occasional 100% charge?

[Yellow Buddy]

@MickeyAO can lead us to water, but alas, he can’t make us drink!

Maybe @MickeyAO isn’t trying hard enough…

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[Newton]

Charging to 100% and then driving to under 20% may help to recalibrate the BMS but it is still not good for the batteries. Read the link below.

In the recent truck race across America by Out Of Spec reviews, Kyle's dad (Team Lightning) has found out that there is NO buffer past zero, or a little earlier. It had to be towed the remaining 5 miles to the charger. Earlier his Dad had to push it to a charger. They really test the limits, I'm glad that they do this thing so that we don't have to.

A dilemma for me is that the BMS drift seems to be really inaccurate in this truck - I'm not talking about the guess-o-meter, but the percentage of battery that is shown. Using car scanner, I can see that my Kia always reports less battery percent than it thinks that it has, but the Ford reports more than it thinks it has - sometimes but not always. Right now I'm showing 63% on the gauge, but internally the truck thinks it is at 59.6%. Which one is right? Probably neither. I charged to 100% this morning or so it said, the gauge read 99%, internally the truck said it was at 91.74% and the total kWh on my 98 kWh battery is shown as 90.65. It does not seem to be a linear difference, and the assumed kWh in the battery relative to what I know that I have varies based on the state of charge.

There is a procedure on the Mach-E forum (not from Ford) to recalibrate the BMS but it involves a 100% charge and then driving to nearly empty (plus some other steps.) So is it worth the stress on the battery to have an accurate BMS.

Ford told Kyle that there needs to be 20 minutes of rest between charging and driving for the BMS to recalibrate itself based on the no load battery voltage. I think the issue is deeper than that. The only hard data point I can throw in at the moment is that when you tell the truck to charge to 80%, it will stop charging at 80% indicated, not what it internally thinks the battery percentage is - which is very odd. The lead acid systems that I have dealt with determine the cutoff point based on charge acceptance rate and voltage so it was strange to see everything shut down at exactly 80% indicated.

Recalibration

 

[WRSNH]

I normally plug in each night and charge to 85% (thank you, @MickeyAO ). Yesterday I set the truck to charge to 100% for a trip but stopped at 99% so we could leave. It got me wondering: Is there any benefit to charging all the way to the “full” 100% every once in a while? Voltage balancing?

Possibly not relevant, but my phone is set to charge to 80% routinely but every once in a while charges to 100% because Apple decided it should. Just made me wonder.

A little more background for my question: I stopped at 99% because the truck estimated another 45 minutes to go from 99% to 100%. Relatively little energy would have been added to the pack at that point and we needed to get on the road. What, if anything, would have been going on in that last 45 minutes I abandoned besides a very slow charge rate? Anything that might suggest next time I should allow more time and let it complete its cycle?

I‘m not interested in tapping reserves not generally available, or in pushing the limits of the battery. I’ll do 85% charge normally, charge in small increments when I can, and try to stay above 20%. But if I need to go to 100% for a trip (right before I leave), I’m not going to sweat it. Perfectly happy to let others decide what is right for them. I’m really just curious about what is going on with the battery at that charging endpoint. Thanks for any insights on this.

 

[Dukhudo]

A little more background for my question: I stopped at 99% because the truck estimated another 45 minutes to go from 99% to 100%. Relatively little energy would have been added to the pack at that point and we needed to get on the road. What, if anything, would have been going on in that last 45 minutes I abandoned besides a very slow charge rate? Anything that might suggest next time I should allow more time and let it complete its cycle?

I‘m not interested in tapping reserves not generally available, or in pushing the limits of the battery. I’ll do 85% charge normally, charge in small increments when I can, and try to stay above 20%. But if I need to go to 100% for a trip (right before I leave), I’m not going to sweat it. Perfectly happy to let others decide what is right for them. I’m really just curious about what is going on with the battery at that charging endpoint. Thanks for any insights on this.

I typically charge to 90%, but had some questions on the BMS, so I tried to recalibrate it.

I just charged to 100% the other day. For me 99% displayed was only 90% HVB SOC in car scanner. it kept charging at 6kwh for another 2 hours until it topped out at 100% HVB SOC and 131kwh where it stopped taking a charge. I had to unplug and replug for the display to read 100%.

 

[brewski]

Range is the advantage.
I guess there there's all the electrical black magic everyone is mentioning.
I follow the Ford 90% for normal use.
I charge to 100% about 4 times a month for my airport run.

 

[Newton]

This is kind of a happy coincidence because I just sort of did that. Like you I had to leave before the truck stopped charging but this is the last few minutes, when the display was showing 99%. It was 100% just a minute or two later because my wife noticed it. I don't know if the charging would have shut off at 100% indicated like it does if I tell it to charge to 80%. I hope not. I do not know why the Energy kWh stopped being recorded, just before I left it was 90.65 kWh (top graph), 91.74% Hvb State of Charge (middle graph) and 99% indicated (bottom graph.)

You can see that the truck's idea of the internal charge of the battery keeps rising non trivially even after 99% is reached, so if your goal is to get as far as possible on one charge you want to keep it plugged in. Note this is a SR truck with a 98 kWh battery usable supposedly, so I think that my truck has drifted below reality. I have never seen an indicated range anywhere near the EPA but in reality on my most recent long trip I was able to get more than the indicated range. (I didn't drive to zero, it just kept readjusting.)

 

[Newton]

And this is what I find really strange - this chart shows the indicated state of charge (blue) vs the internal state of charge (green) while driving along with the estimated total energy left (red). These are both estimates but they should both be based on the same data, so you would think that the difference between the two would be constant. It isn't - the indicated state of charge initially drops much faster than the internal and the total energy left just does its own thing. Why?

 

[Newton]

I would like to know how much of the truck's behavior is determined by these parameters. It seems like the time at which it cuts off charging is determined by the indicated battery percent, so you might not be charging the battery as much as you think you are (or in the worse case, charging more than you think.) I hope that the actual charging decisions are based on observed parameters like temperature and voltage instead of coulomb counting with occasional resting voltage recalibration.

 

[VTbuckeye]

This is kind of a happy coincidence because I just sort of did that. Like you I had to leave before the truck stopped charging but this is the last few minutes, when the display was showing 99%. It was 100% just a minute or two later because my wife noticed it. I don't know if the charging would have shut off at 100% indicated like it does if I tell it to charge to 80%. I hope not. I do not know why the Energy kWh stopped being recorded, just before I left it was 90.65 kWh (top graph), 91.74% Hvb State of Charge (middle graph) and 99% indicated (bottom graph.)

You can see that the truck's idea of the internal charge of the battery keeps rising non trivially even after 99% is reached, so if your goal is to get as far as possible on one charge you want to keep it plugged in. Note this is a SR truck with a 98 kWh battery usable supposedly, so I think that my truck has drifted below reality. I have never seen an indicated range anywhere near the EPA but in reality on my most recent long trip I was able to get more than the indicated range. (I didn't drive to zero, it just kept readjusting.)

I usually charge to 60 percent. Usually I get in and it says 60. Sometimes it drops immediately to 59. Sometimes it jumps to 61 or 62.

 

[RonTCat]

I normally plug in each night and charge to 85% (thank you, @MickeyAO ). Yesterday I set the truck to charge to 100% for a trip but stopped at 99% so we could leave. It got me wondering: Is there any benefit to charging all the way to the “full” 100% every once in a while? Voltage balancing?

Possibly not relevant, but my phone is set to charge to 80% routinely but every once in a while charges to 100% because Apple decided it should. Just made me wonder.

Balancing happens above 80%.

 

[luebri]

Balancing happens above 80%.

I’ve only TRIED to charge to 100% immediately before departure for a long road trip. However Fords crappy software has caused me to mistakenly do it a couple time. One of them this morning because I had to shut off my charging locations to charge past my typical 80% the other day in preparation for possible power outage due to weather. i typically would have gotten the extra juice manually using the Ford pass “charge to 100%” option which is currently broken for me. The next night I forgot to turn on my locations and forgot to set my one time charge limit so it went to 100% all in its own. So annoying.

 

[Tom M]

Some people say that you can charge to 100% because there is extra capacity. Others say that you can drive past 0% because there is extra capacity...it can't work both ways. Do we know if we actively charge that capacity or if it's left empty so we don't charge to an actual 100% ever.

I can’t drive past 0%. So I wouldn’t count on that.

 

[Dukhudo]

Just charged to 100%. I didn't quite catch 99% display, but when I did:

HVB SOC - 91.73%
HVB SOC Display - 99%
Energy -118.12 kWh

At 100% display:

HVB SOC - 96.36%
HVB SOC Display - 100%
Energy - 124.72 kWh

So three things:
- 99%-100% is roughly 4.5% or higher (I didn't catch it right when it turned to 99%) and 6.6 kWh. At 2.2 m/kWh this is 14.5 extra miles that can be travelled. This can vary based on how much energy your 100% ends up at.
- I'm not getting the full usable 131 kWh of the battery pack. (Outside temp 60f). I have got 100% HVB SOC and Energy 130.7 kWh once before, but that was using the mobile 240v instead of the mobile 120v I used this time. The truck also seemed to glitch and never reached 100% until I unplugged and replugged the truck back in once it stopped taking a charge.
- Getting from 99% to 100% is painfully slow. On the 120v, it took an extra 6-7 hours. With a 240v charger, this will be a bit faster, but that last bit still slows to the 120v charging speed. So plan accordingly if you want those extra 15 miles.

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