I set up 80% of target charging. But Why does charging stop at 78%?!

[Ssun0108]

I set up 80% of target charging. But Why does charging stop at 78%?!

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[flapjake314]

don't totally understand. in the first picture at the top, it clearly says your car is at 80% with GOM of 180mi. what was the actual car saying when you unplugged it as its SOC?

i'm guessing the "end" number is just wrong, i don't know why though maybe true SOC vs displayed SOC or something

 

[Ssun0108]

don't totally understand. in the first picture at the top, it clearly says your car is at 80% with GOM of 180mi. what was the actual car saying when you unplugged it as its SOC?

i'm guessing the "end" number is just wrong, i don't know why though maybe true SOC vs displayed SOC or something

It actually stopped charging at 78% at 175 miles.

 

[flapjake314]

It actually stopped charging at 78% at 175 miles.

does this happen every time? it happened once to me but just once so i never thought about it that much...

 

[TowPro]

our 23 extended charges at night up top 90% but the timer shuts off the charger at 6am. Later that day (or next) if we use the car its common to see the charge has dropped 1 or 2%.

 

[hybrid2bev]

I set up 80% of target charging. But Why does charging stop at 78%?!

Maybe try charging to 100%, let it run down to <20% and then charge to 80%. That may help calibrate the BMS.

 

[Snakebitten]

Not uncommon for my target 80% to be 79% in the morning when I get in the car to leave.

I chalked it up to a couple of things....

1. 80% isn't 80.5 or 80.99%?
I assume it hits 80% and stops. Right on the cliff from 79.99?

2. Most often my battery finishes charging in the cooler ambients of midnight. So at 8 or 9 am in the tropics, ambients have already increased by 15-20F. Doesn't that marginally increase capacity?

I also noticed that even though I might have dropped from 80.x% to 79.99%, the gom might have only dropped by a mile or 2. Admittedly I have seen it drop 4-5 miles on occasion too.

I don't know if there's any true data to back this theory up, but I am in the process of building a dashboard or two using some applicable PIDs and configuring the displayed values to 2 decimal points. Something the apps and IPC/Sync4 doesn't. If/when I get confirmation, I'll be happy to share here.

 

[Just Lurking]

It happens to me frequently that charge stops at 90% and when I get into the car (potentially many hours later) it's at 89%. I'm sure there is a satisfyingly wonky explanation based on how exactly the car is calculating these charge estimates that someone like @Mach-Lee could probably expand on.

But in general, I try and keep in mind every time I see battery percentages that these are at the end of the day estimates. There is a chemical process going on inside each of the different cells that make up a battery (hundreds of cells for the Mach-E battery, obviously far fewer for a consumer device battery). We can't see inside the battery to see the chemical processes directly, so the battery state of charge (SOC) has to be inferred from things like voltage levels or by calculating how much energy has been fed into the battery during a charge cycle.

Very slight variations among the different cells have to be averaged out, the voltage levels themselves can fluctuate very slightly due to environmental conditions, and calculations such as how much energy was fed to the battery have to exclude estimates for charge losses due to heat.

It all results in a fairly sophisticated estimate of battery percentage which is reported to us on the dashboard, but at the end of the day that's what it is, a sophisticated estimate.

 

[Pioneer74]

This happens to my Lightning. I set the charge to 85%. Dash says 85% before I hit the start button. Guage says 84% when I hit the start button. Put it in reverse, move 2 feet and it goes down to 83%.

Every day.

 

[zvez]

would it stop charging if it hit your end time charging window (if it was am?)

 

[Snakebitten]

I built the dashboard for the Mach-E last night (OBDlink) and can now monitor the charging activity as well.

The top 2/3'rds is while the car is in use. The bottom is for monitoring while charging, or immediately thereafter. By adding a decimal points I should be able to see what the SOC (displayed) is when the target charge is hit and the car inhibits further charging.

(The screenshot was with trickle L2 session but car/OBD on. I'm letting the BMS "balance" the cells/modules. Or at least I think I am) ?

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