Ford IDS Data

OK, I wasn't aware the service manual provided that information. So I believe you are saying that active cooling doesn't begin until 95 F battery temperature, is that right? That's consistent with my observation that battery temperatures stabilize around 98 F on reasonably hot days.

That's not what I hoped to discover, however....

michael said:

Based on my OBD scanner, it appears that the thermal management system doesn't start cooling until the battery temperature is around 98 degrees F. In normal use(driving and charging) it's typically in the 80's and 90's even with moderate (60's, 70's outside temp) Do you agree?

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Does the Focus Electric do nothing to cool the battery until it hits 98F? Does the active thermal management behave differently in the summer vs winter?

I ask because our FFH behaves very differently between summer & winter for how the car approaches HVB temps. In the winter (<40F ambient temp) the cooling fans turn on at 70F and try to keep the battery from getting any warmer than 72F. If the temp exceeds 72F then the fan speed increases to bring the battery temp back under 72F. If the temp drops under 70F then the fans turn off.

In moderate (50-70F ambient temp) weather the FFH won't turn on the HVB fans until the HVB temp reaches 78+F and it appears to try to keep the HVB temp between 78 & 80F.

In hot summer weather (>80F ambient temp) the FFH doesn't try to cool the HVB until its temp is 90+F. The highest I ever saw the HVB temp was 104F last summer in our FFH. That was on a 95+ degree day after the car had been driven and then parked in the sun for hours and then driven again.

Often our climate in MN jumps right from cool spring weather of <70 degrees to hot summer temps of >80 degrees so I don't have data for how the Fusion Hybrid manages HVB temps when the ambient temp is >70 but <80F.

Obviously the battery in the Focus Electric will heat up more quickly since it's being used more than the battery in the hybrid, but I'm curious if the Focus also adjusts its thermal management behavior based on outdoor temps.

dmen said:

1. Displayed SoC has been observed by me and others to not correlate linearly with displayed energy usage. With a full battery, SoC drops quickly compared to energy use at first, showing 10% used when only 1.5kWh have been used, then 25% at 4.5kWh, 50% at 9.5kwh, and so on. If energy use was calculated from SoC "sampling" rather than measured, wouldn't it correlate directly with SoC?

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Are you talking about Displayed SOC or Absolute SOC? I can measure both on the Fusion Hybrid & my parents' C-Max Energi. Displayed SOC represents how full the dash icon appears. Absolute SOC gives an absolute reading from the battery. For the FFH, the relationship is linear and allows us to determine what range of Absolute SOC is used by the car by creating a regression equation where I can take Displayed SOC and use that number to calculate the Absolute SOC at any given point.

dmen said:

1. Displayed SoC has been observed by me and others to not correlate linearly with displayed energy usage.

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It's not perfectly linear, but it seems "fairly" linear.

Here are my observations from today, driving from 100% to 0% SOC, with trip meter reset before setting out. I noted the kWh consumed displayed by the trip meter for as many unique SOC percentage points displayed in the MFT screen as I could. (Any missing values, of which there were only a few, were linearly interpolated.)



The purple line shows the variance between my observed energy consumption (in red) at each SOC percentage point compared to a perfectly linear consumption (in green). In this particular observation, the variance is never more than 4%. Yes, not linear. But, not "wildly" non-linear either.

Of course, my (or anyone's) observations through the car's displays can only be accurate to 1 percentage point (for the SOC) and 100 Wh (for the energy consumed), since these are the intervals used by the displays. Thus, the "resolution" (and "timing", as well) at which the values are observed will introduce some variance on its own (although clearly this cannot account for a variance of 4%, which represents over 700 Wh, but it is something to consider).

Somehow (and very nervously, I might add) I arrived home with an actual 0% SOC, and the car popping up a "Battery Depleted" warning about 500 yards from my house. I actually didn't intend to cut it so close, but I suppose it was good for the purposes of my observations. According to the trip meter, my total energy consumption was 18.5 kWh (which is the scale of the left y-axis of the graph).

dmen said:

Sampling of SoC seems to be inherently inaccurate. I've never known a rechargeable battery's SoC display to behave very consistently over full range.

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This may not be a fair comparison.

We should not automatically assume the SOC display of the FFE (by which I mean the percentage shown in the "energy" screen on MFT) is "inherently inaccurate". The other devices you mention (phones, laptops, etc.) -- who know's how their displays work? For all we know, those devices migth have artificial software-implemented biases to make them appear to function a certain way (remember the debacle with the fake "signal strength" meter on iPhones a while back -- that kind of thing). I agree, sometimes those devices do wacky things. But, my FFE doesn't seem very wacky (see the graph above).

dmen said:

3. Battery's effective usable capacity varies with ambient temperature (near 20kWh at ideal temps over 60F, ~17kWh at freezing), but max and min SoC do not vary with ambient temp.

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The minimum SOC doesn't need to vary, it is whatever (absolute) voltage the FFE considers "empty". We don't need to know the maximum SOC. The energy consumed can be computed from the minimum SOC, the current SOC, and the SOC at the last reset of trip meter (the maximum of which can freely vary with temperature, having the correct proportionate effect on the energy computations).

dmen said:

4. As one's battery capacity inevitably decreases, relative SoC will not.

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Again, this should not be an issue, for the same reason that temperature variation should not be.

The reasons these variations should not matter is because the trip meter uses only a known "zero point", the "last reset" point, and the "current point" (which can be used to compute the energy consumption relative to the other two). The maximum values of the latter two points is not important (but they will naturally vary with temperature and degradation).

dmen said:

5. Measuring two-way energy movement isn't all that complex.

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Perhaps, but measuring the SOC seems like it could be even simpler.