After driving our new C-max Energi a little over 800 miles and 35 charges, we still have almost 3/4 of the original tank of gas (Mmmm, dealer gas), and getting lots of good data on how the Energi behaves. We commonly see an estimated 26 miles remaining just after a charge. We have only run the battery to 0 miles four times, clocking 19.9, 20.0, 22.7, and 23.6 EV miles (average 21.55) each of those times.
Combining the estimated miles remaining with the actual EV miles driven at the time of re-charge gives a sense of total range performance/expectaion. For instance, if I drive 18.8 EV miles and it says I have 4 remaining, I might infer that I had 22.8 total EV miles available, without depleting the battery completely to find out. I trust such estimates more when few miles remain than when the battery is completely full. Let's see how the Energy actually does:
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What we see in the plot above (may need to click to enlarge) is that the Energi tends to be optimistic: early estimates approach 26 miles, while later (more reliable) estimates cluster around 22 miles. If we fit a trend line, we find that the zero intercept is 21.2 miles, and the "optimism factor" is 17% (each actual mile remaining will be estimated as 1.17 miles remaining). But on the whole, I am very pleased: 21 miles is truth in advertising. We drive our car in a varied style: no repetitive (commute) path. I would estimate that 40% of the miles are freeway miles. We are not using climate control.
While I'm posting, I should update my charge performance data, as a follow-up to a previous post. Lots more data, and clustering tightly around a line that indicates 72% charge efficiency (takes 1.4 times as much wall-plug energy as battery energy) using the Ford-supplied charger at 120 V. Note that a response in that thread had a plot with very large scatter. I have not seen any indication of scatter. It's getting boring enough that I may stop recording. I am constructing a 240 V charger now (OpenEVSE) and will be able to add data on this behavior in the future.
So here are the updated plots. I added a MPGe conversion scale on the kWh/100 mi plot. Note that the car reports values corresponding to the blue dots (around 130 MPGe), while the EPA rating uses actual wall-plug energy, corresponding to the green dots around 100 MPGe. Our car is reporting about 133, while actually getting about 96 in the EPA sense. And one final data point before I shut up: a 240 mile round trip to Pasadena, taking it easy for break-in reasons (60-65 mph), produced 47 MPG on gasoline! Very happy about this!
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mpkwh-update.png 73.56KB 25 downloads