Checking battery capacity - 80.9 kW? WTF?

[JeffGo]

2021 Mach E Premium, AWD, Extended Range

I charged to 100% today (Jan 19, 2022)

Checked using OBDLink software, parameter EV Battery Energy to Empty = 80.9 kW, WTF? Maybe that's partially responsible for poor range (other than lower temps)? At 100% this time, GOM said 171 miles.

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[Maquis]

Energy should be kWh, not KW.
What was the battery temp? I would probably expect lower capacity at low temperatures.

 

[JeffGo]

Energy should be kWh, not KW.
What was the battery temp? I would probably expect lower capacity at low temperatures.

Yes, should be kWH but the app displays as kW.

Outside temp was 49F

 

[JeffGo]

Charger was plugged in for 24 hours before, the last 2 hours of that was charging from 90 to 100%.

 

[Maquis]

Yes, should be kWH but the app displays as kW.

Outside temp was 49F

If the units are wrong, maybe the number is, too?

The temp in play here would be the actual battery temp, maybe available in your OBD link.

 

[JeffGo]

If the units are wrong, maybe the number is, too?

The temp in play here would be the actual battery temp, maybe available in your OBD link.

I’ll check tomorrow.

 

[Maquis]

I’ll check tomorrow.

To be clear, I don’t know the capacity vs temp curve of the MME battery, but EV batteries do have temperature-dependent capacities. It will be interesting to see what you find.

 

[JeffGo]

To be clear, I don’t know the capacity vs temp curve of the MME battery, but EV batteries do have temperature-dependent capacities. It will be interesting to see what you find.

Would also be good to know what the temperature was when they rated the capacity …

 

[Maquis]

Most battery specs I’ve seen use 25C.

 

[benk016]

That value is not very accurate I've discovered. Mine will jump between a few numbers if its just sitting there. Seems like it settles in more if you've been driving instead of sitting.

 

[Mach-Lee]

The value will go down in colder temps due to normal cold-weather capacity loss. Fords capacity model may be a bit conservative still in lower temps.

 

[Mach1E]

2021 Mach E Premium, AWD, Extended Range

I charged to 100% today (Jan 19, 2022)

Checked using OBDLink software, parameter EV Battery Energy to Empty = 80.9 kW, WTF? Maybe that's partially responsible for poor range (other than lower temps)? At 100% this time, GOM said 171 miles.

This may actually explain a lot about some of the cold weather GOM complaints.

Part of it is the battery being less efficient in the cold.

But maybe the rest is that the battery doesn’t let you charge to 100% (even though it says 100%).

The good news about this? Your cost per mile in the winter may not be as bad as you think.

 

[SpaceEVDriver]

At cold temperatures, Li batteries typically have lower overall capacities, not just lower efficiencies. It's also important to precondition your battery before driving in cold temperatures. Not just for range reasons but also for longevity reasons.


(Emphasis in the quote is mine, I removed the citations for readability. Those can be found in the original paper.)

Steinstraeter et al (2021; https://doi.org/10.3390/wevj12030115)

"Cold conditions cause declined reactivity and diminished ionic conductivity in Li-ion cells, which affects their usable capacity and impedance. In this context, Nagasubramanian et al. showed that under extreme cold conditions (−40 ◦C) a Li-ion cell can lose up to 95% of its energy and more than 98% of its power capability compared to performance levels at 25 ◦C. Similar research shows that a cell’s capacity can drop by up to 23% at −20 ◦C compared to the capacity at 25 ◦C. Besides these temporary losses in cell performance, low temperatures also promote Li-plating, which can lead to a permanent reduction in cell performance. Li plating is the deposition of metallic lithium on the cell’s anode. This reduces the number of cyclable Li-ions and increases the cell’s impedance. Both of these effects are in part irreversible, leading to a permanent reduction in the cell’s energy and power capability. To reduce such cell aging processes, the battery management system (BMS) limits charging and discharging currents at low temperatures. Steinstraeter et al. showed that a BEV’s ability to recuperate is strongly dependent on the battery’s temperature. Limited recuperation under cold conditions is a particularly critical factor of a BEV’s driving range, since the energy restored through regenerative braking under warm conditions (without limitation) can contribute 18% of the total energy required for a trip."

 

[Accord07]

I haven't looked at those numbers when SOC was 100%, buy did extrapolate while SOC was in the 60%-70% range - it came to 79kWh when HVB temperature was reportedly 11C (min 9C, max 14C) and 89kWh at 25C (18C - 27C).

 

[Maquis]

I haven't looked at those numbers when SOC was 100%, buy did extrapolate while SOC was in the 60%-70% range - it came to 79kWh when HVB temperature was reportedly 11C (min 9C, max 14C) and 89kWh at 25C (18C - 27C).

Your 79 @ 11C matches the OP’s point pretty closely.

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