Battery Charge - Charge Capacity v. Percentage Charged

[NeuroDawg]

I recently purchased a new '24 Flash, after my '23 XLT ER was returned to Ford via buyback. I never had any issue like this with the XLT, and I'm trying to figure out why I'm seeing what I'm seeing.

I consistently charge to 90%. On my XLT this would reliably give me a charge of 115-118KWh (displayed through Car Scanner Pro). On a road trip I took in October, the two times I charged to 100%, gave me 127.4KWh and 130.66KWh, exactly what I would expect.

However, with my Flash, I charge to 90% and I'm seeing capacity of ~105KWh. This morning when I went to work the display in the car said 90% charged, car scanner pro showed HVB SOC Display to be 89.5%, and battery charge of 104.75KWh.

This has me concerned. 104.75KWh should display ~80% charge, not 90%.

Can anyone explain this to me? Is it temperature related? It's been the same with overnight lows in the high 20s to mid 40s. Is it something else I haven't thought about? Is it a matter of a module reset, or disconnecting the 12v for a while to allow a complete system reset?

I currently have my truck plugged in and am charging to 100% to see what I get. I'll report back. For what it's worth, this truck has a build date of 3/24 and I bought Jan 30, so it sat on the lot for a few months. Also, my 12v consistently reads low, 75-80%. I've been able to get it to 92% after leaving it on a trickle charger overnight, but then it drops to the 70s-80s. I have an appointment with service in a couple weeks to get that checked/replaced.

Sponsored

 

[mrtyndall]

I have a similar issue with my flash, at least with range. I need to check the battery tonight when it charges up and see how many KwH I have

 

[NeuroDawg]

I have a similar issue with my flash, at least with range. I need to check the battery tonight when it charges up and see how many KwH I have

I purposely left the GOM range out of my post because of how it fluctuates with temperature and driving style. This is all about the battery capacity and charging percentage reported by the truck.

 

[Firn]

Leave the truck plugged in but turn it on (run). Iirc it should then warm the battery to 60f. I expect with the higher battery temp you will see a higher capacity.

 

[NeuroDawg]

Leave the truck plugged in but turn it on (run). Iirc it should then warm the battery to 60f. I expect with the higher battery temp you will see a higher capacity.

Probably. Does that mean that the percent charged display changes because the truck says to itself "in this condition I can only fill the battery to 118KWh, and 90% of that is 105KWh"?

I guess that I expect percent charged to represent a percent of the 131KWh battery capacity.

But... I can see why it might do it the other way. Otherwise in the cold temps when the battery only gets to 115KWh and says 87% charged, everyone would be saying "Why doesn't my truck charge to 100% when it's cold?"

 

[Firn]

Probably. Does that mean that the percent charged display changes because the truck says to itself "in this condition I can only fill the battery to 118KWh, and 90% of that is 105KWh"?

I guess that I expect percent charged to represent a percent of the 131KWh battery capacity.

But... I can see why it might do it the other way. Otherwise in the cold temps when the battery only gets to 115KWh and says 87% charged, everyone would be saying "Why doesn't my truck charge to 100% when it's cold?"

I can only offer my thoughts here.

SOC only makes sense to be related to voltage. Something along the lines of 100% being 4.09v per cell, 90% being 4.05, 80% being 3.95v, etc. You don't charge to a capacity, you charge to a voltage level.

Capacity is a value determined by voltage, temps, and likely a number of other factors.
When the battery is at 4.0v it has a different capacity at 100f than it does at 10f. At high temps it has a higher capacity than at low temps.

When it's cold out capacity is lower. You can't charge to 120% to make up for it, so SOC isn't a measure of capacity it's voltage (max voltage is max voltage hot or cold).

 

[Firn]

An interesting thought though.

Ford already limits maximum voltage to a number lower than is common for Lithium NMC batteries. We all expect this is to ensure the battery makes it through the warranty.

However battery degredation is much lower in the cold. Charge two batteries to 90%, the one in the colder climate will last longer.

So Ford could change the maximum allowable voltage based upon battery temp, letting batteries that are cold charge to a higher voltage. This would give cold weather drivers more range, but without being any worse for the battery than in warm climates.

 

[RickLightning]

You need to charge to 100%, and leave it sit on the charger, as the cells balance. See what the reading is when the battery is nice and warm. Then, if it's still low, you need to run it down to 10 - 20%, and charge it back to 100% again, and then look.

As stated, temp affects energy. On a recent trip out west in the bitter cold, here are two readings of the same kWh. Note the temperature and state of charge differences:

Battery Temp SOC% kWh
89.6 85% 114.21
46.0 93% 114.20

At 90 degrees, 114.2kWh was displayed at 85% SOC. At 46 degrees, the same energy was displayed at 93% SOC.

Sponsored