Theoretical Estimate of EV range "consumed" at various speeds and grades

I'm not sure that's totally out of sync, but there are some complicating variables related to my simplifying assumptions in the model. First is the PiP's internal EV range calculation as I understand it is not simply a linear calculation, so its going to throw some "error" into the mix from the perspective of this calculation by adaptively updating its estimate based on driving conditions and style. If you have a way of displaying actual kWh used/gained that would be a more direct indicator. Second the calculation is based on sustained EV speed on a fixed grade, so if there is a difference in uphill vs downhill speed or if speed is not constant in either case that will also introduce error. Third, if the downhill is sufficient to accelerate the vehicle while gliding that will also violate the fixed speed assumption, as some of the energy that would have been seen as bonus EV range is being spent accelerating the vehicle. Speed can be controlled by regen, but regen is by definition less than 100% efficient (more like 33% efficient as I recall) so energy will be lost.

If I understand what you're saying, you use 1.0 miles of EV range to go up the hill, and -0.2 miles coming down. In an ideal sense, if all the assumptions above were valid (no EV range calc error, constant speed both ways, etc) that would indicate the distance traveled should be about 0.4 mi, with a +0.6 mi penalty uphill and a -0.6 mi bonus going downhill. If the distance is really exactly 300 yards, that's only ~0.2 mi so there is a source of error there somewhere. Since the downhill EV range used is <0, I'm assuming that means you're having to brake to maintain speed and/or the EV range calculation is adapting its Wh/mi estimate based on the downhill run (which it could also be doing on the uphill run) or you are accelerating downhill.

If we assume the distance is 0.2 mi instead of 0.4, then the uphill penalty would be 0.8mi. At the same fixed speed, you'd expect the downhill bonus to be -0.8 mi resulting in -0.6 mi net, but the observed is -0.2 mi. In this case, I'd chalk the lost 0.4 mi of EV range up to either energy consumed accelerating the vehicle, energy lost to regen efficiency, non-linearity of the EV range calculation or some combination thereof.

FWIW this observation doesn't really have anything to do with the accuracy of the calculations above, its more a test of the validity of the physics assumptions. To the first order, the extra energy the vehicle uses to move the vehicle uphill relative to flat is "stored" in the mass of the vehicle as potential energy. When the vehicle goes back down the same hill that potential energy is released to help move the vehicle forward. By doing this calculation relative to driving flat at the same speed, the effects of friction and wind resistance are effectively canceled out. There is an assumption that the efficiency of the drive system is the same in both directions, which is a pretty decent assumption for an electric motor, particularly for gradual grades For an ICE (or even better a Prius) drive efficiency can actually be higher than flat when going uphill, and if the vehicle can also coast downhill efficiently (such as glide or warp stealth mode) then the result of the total uphill/downhill event can be less total fuel consumed than flat driving the same distance. I actually see this frequently in my Gen2 when I take the kids up the mountain and back on the way to work, vs. taking my normal flat route.

Rob

 

Ahhhhh The ratios will be different for a different vehicle, but the same principles should apply. Interesting that speed doesn't seem to affect consumption. Route I can kind of understand, it will likely be dominated by the total elevation change.

 

The basic idea looks right on! Seems like some fishiness in some of the values though. Put in my commute (80km/h 15.5km, ~30m elevation change), and it says the Volt range is 107km and Leaf is 116 km? Digging around a little, it seems like the Volt battery capacity used is gross (16kWh) rather than net (10.6kWh?), while the Leaf is Net? (20kWh). Also seems fishy that the Volts calculated kWh/100km consumption is 10-15% lower than the Leaf's, as I'd understood most testing to show the Leaf a bit more efficient if anything. As with the EV Calc the tricky part is often inputting the right values into the model. Would love to see more info on how they do the calcs. Seems like it does a great job of parsing the goggle data into chunks with elevations change!