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Welcome to The Circuit – the official place to connect with other EV drivers about the BMW i3,
the BMW i8, and the electric lifestyle. Share stories, ask questions, and continue the conversation
as we all journey into the future.
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Post by bwilson4web on May 13, 2016 9:02:01 GMT -5
A soon to be owner of a used i3-Rex, I wanted to share a technique used in the Prius community to generate this graph:
roll-down coefficients - found in "Test Car Database" at epa.gov, these three parameters in a formula can provide the power (typically hp) for a car at any give speed.
vehicle overhead - I swagged 746W (i.e., 1 hp) since this close to what our Prius measures. If someone has a better value, I'll use it
traction battery capacity 18.7 kWh - I used 22 kWh * 85% to get the same net value found on the BMW site
added range extender max power bar - my understanding it is rated at 34 hp but it isn't clear if that is engine shaft power or net generator power
So I SWAGGED some values. When we pickup our used i3-Rex, we'll have about 800 miles from Houston along the Gulf Coast and hopefully validate some of the points. Regardless, I've attached the spreadsheet so folks can see what I did.
One question for the community, is there a shop manual and/or electrical schematics available? I've bought them for the Prius (actually all cars owned) simply because I am curious and sometimes use them for self-maintenance.
FYI, after reading the Owner's Manual, I realized 'mi/kWhr' would be a more useful metric:
Understand this is just a first order approximation. I will need some benchmark metrics at different speeds (20, 30, 45-55, 75-95 mph) to validate and adjust the model.