Battery Percentage Giving Fake News?

[FloridaMan655321]

I'm still charging via 120v (240v getting installed next week) and I've started to notice something that I wanted to run by some of you. I don't think there is an issue with the battery, but more software.

As I'm charging via 120v I mostly charge on the weekend as this is off peak times and I don't have a long commute to work during the week. I do sometimes charge at night as well. What I've had happen a few times is when I have the limit set, say to 80% or 85%, and the charging hits this number, sometimes (not every time) when I leave to go to work in the morning the battery will drop almost 5% in under 1 mile away from my home. This doesn't seem to happen if say I set the charge limit to 85% and it only gets to 83%, then everything is as normal.

Also, after this sudden drop of ~5%, everything acts as normal. It's not like it keeps dropping fast. I'm thinking the truck is just giving me some fake news and thinking it's 85%, but really it's 81% (or saying it's 80% and it's really 75%).


I hope this make sense, and as I said it's not every time, but it has happened a few times now so I'm wondering if anyone else has experienced this? I'm also not concerned as I'm about 99% sure this is a software issue and not a hardware issue.

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[Tfarrell73]

Sounds normal if it's a cold morning. Battery is using power to warm the battery. Watch the This Trip stats to see where the power is going

 

[FloridaMan655321]

Sounds normal if it's a cold morning. Battery is using power to warm the battery. Watch the This Trip stats to see where the power is going

If that were true, wouldn't I expect that even if the truck doesn't charge fully to where I set the limit? And wouldn't I see this more often? Each morning when I leave it's around 60f or more, being in FL and all. I also don't remember seeing this kind of change each day when we had a recent 'cold spell' and I was leaving at around 50f

 

[Newton]

Yes. It is very strange and seems different than my other EVs. With an ODBII dongle you can kind of see what is going on but it is still strange. There is an internal state of charge and a visible external state of charge, and they have different curves! When you charge to 80% the truck will have a smaller number internally, but the ratio will swap as the battery depletes. Neither of the numbers is all that accurate in my opinion, I have recorded a lot of data on longer trips.

The odd thing is that the truck’s behavior seems based on the state of charge that it displays rather than the state of charge that it knows it is at. It will start limiting DC fast charging (on my SR) at exactly 81% displayed without regard to what the truck really thinks the battery charge really is. I do not drive the battery low often but it seems to always start limiting power at the same place on the displayed state of charge rather than the internal one. When I charge to 100% on an AC charger I can see that the internal state of charge is less than 100% for quite a while after the external state shows me fully charged, but it does eventually reach near 100% (which negates the theory that the internal state of charge is showing me the reserve).

There is inconsistent behavior when using regen. I drove to the top of one of our mountains here with predictably bad effects on the uphill side going as low as 1 mi/kWh. Going downhill I expected to see the behavior of my Kia that shows 99 mi/kWh (I thought it would make a nice picture) but it stayed pegged at 0 mi/kWh for miles and miles - and the state of charge and range did not increase. In reality it did regen based on how far I made to the next recharge. A recent software update seems to have changed that behavior somewhat.

One of the issues that any EV battery management system has to deal with is that immediately after charging the battery voltage is artificially high. If you are measuring the state of charge by battery voltage, the only voltage that counts is after the battery has been resting (neither charging nor discharging) for some time. Obviously this is not how we use EVs so some software magic has to happen and it happens differently in Ford than other EVs.

It would be awfully nice if some Ford guru could explain in detail the relationship between the displayed state of charge, the range, the internal state of charge and the actual charge. Batteries are complex, I would almost rather that they just showed us the voltage and let us learn how the truck behaves at those voltage levels.

 

[Grease Lightning]

I'm still charging via 120v (240v getting installed next week) and I've started to notice something that I wanted to run by some of you. I don't think there is an issue with the battery, but more software.

As I'm charging via 120v I mostly charge on the weekend as this is off peak times and I don't have a long commute to work during the week. I do sometimes charge at night as well. What I've had happen a few times is when I have the limit set, say to 80% or 85%, and the charging hits this number, sometimes (not every time) when I leave to go to work in the morning the battery will drop almost 5% in under 1 mile away from my home. This doesn't seem to happen if say I set the charge limit to 85% and it only gets to 83%, then everything is as normal.

Also, after this sudden drop of ~5%, everything acts as normal. It's not like it keeps dropping fast. I'm thinking the truck is just giving me some fake news and thinking it's 85%, but really it's 81% (or saying it's 80% and it's really 75%).


I hope this make sense, and as I said it's not every time, but it has happened a few times now so I'm wondering if anyone else has experienced this? I'm also not concerned as I'm about 99% sure this is a software issue and not a hardware issue.

What you are experiencing is normal not normal. Seems there might be something odd with the BMS ability to self regulate in some Lightning.

I am current collecting data and will make a new thread soon, but mine hasn’t done the drop, but inaccurately displays the SOCd compared to the actual kWh the truck is showing. Sometimes as much as 10 kWh for what the SOCd should show.

I took it down to 3-4% this weekend and the BMS finally was truthful then slowly charged it back up to (took 20hr at 32amp to fully balance). At the high end it was still off the 131 kWh but was closer to normal giving the temps are considerably below the ideal 70 deg.

Todays fun is the SOCd is still showing 100% at 112 kWh (what should be 85%) ….so yeah welcome to normal not normal.

Love the truck, hate the BMS…..

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