regen efficiency

[tboult]

Just PMed you with the link to the data.. its sampled at 1sec intervals with gps and speed shown.
Not perfectly constant in the speed, with a turn in the middle of the drive. All in L with CC set on as soon as could get it to stick.


Gain was between 0.314 kWh and 0.377 ( the OBDII accuracy limit is 0.062745362kw (after scaling), so its quantized.. hit .314 after 89.1m of elevation gain.. but kept going down to 93.7 in elevation gain so more than .314 and less than .377.

The speed limit in the neighborhood was 25mph.

I can sample this again tomorrow (its on the way to work) -- could even do multiple samples if you think that would help to provide more meaningful answers.

I think your road-load equation has a problem as the car is going down a 4-5% grade for most of this so it does not need anything from the pack. If I let it coast in drive down a hill like that (well a similar on I70), it would be doing over 75mph with while doing regen. Rolling resistance may also be lower on a hill as force on the tire is not directly perpendicular to the direction of travel.

[George S. Bower]

Just PMed you with the link to the data.. its sampled at 1sec intervals with gps and speed shown.
Not perfectly constant in the speed, with a turn in the middle of the drive. All in L with CC set on as soon as could get it to stick.


Gain was between 0.314 kWh and 0.377 ( the OBDII accuracy limit is 0.062745362kw (after scaling), so its quantized.. hit .314 after 89.1m of elevation gain.. but kept going down to 93.7 in elevation gain so more than .314 and less than .377.

The speed limit in the neighborhood was 25mph.

I can sample this again tomorrow (its on the way to work) -- could even do multiple samples if you think that would help to provide more meaningful answers.

I think your road-load equation has a problem as the car is going down a 4-5% grade for most of this so it does not need anything from the pack. If I let it coast in drive down a hill like that (well a similar on I70), it would be doing over 75mph with while doing regen. Rolling resistance may also be lower on a hill as force on the tire is not directly perpendicular to the direction of travel.

Thx, Got the spreadsheet
your right I think I was a little high on road load. based on this old leapcad analysis http://www.leapcad.com/Transportatio...Simulation.pdf it's probably more like 2.3 kw at 24 mph which works out to .10 kwh/mi.

using that number I get a regen efficiency of 95% (highly doubtful).
If I assume zero road load i get 72% regen efficiency.

So the answer is that the real regen efficiency in this case is pretty darn good. If we split the difference it comes out at 84% which makes sense.