Once again, I’m going to go back to my napkin calculations to figure how big a pack I want for my target range of 75 miles or so. The simplest way to get to that is to look at the two documented bikes out there, grab a quick kW/mile figure from them, and you should be close. Here are the Brammo Empulse specs:
|Battery Pack Capacity||9.31 kWh (nominal), 10.2 kWh (max)|
|Driving Range||City: 128 miles / 206 km||Highway: 58 miles/ 93 km||Combined: 80 miles / 129 km|
The Zero SR:
|Max capacity (wo/w Power Tank)||12.5 kWh||15.3 kWh|
|Nominal capacity||11.0 kWh||13.5 kW|
|Range||ZERO SR zf12.5||ZERO SR ZF12.5 +Power Tank|
|City||151 miles (243 km)||185 miles (298 km)|
|Highway, 55 mph (89 km/h)||94 miles (151 km)||115 miles (185 km)|
|» Combined||115 miles (185 km)||141 miles (227 km)|
|Highway, 70 mph (113 km/h)||77 miles (124 km)||94 miles (151 km)|
|» Combined||102 miles (164 km)||125 miles (201 km)|
The Energica Ego, just for comparison to a bike more similar in performance, has an 11.7kwh pack and the range numbers are 190 km @ 60 km/h, 150 km @ 80 km/h and 100 km @ 100 km/h. That translates to 118 miles @ 37 mph, 93 miles @ 50mph and 62 miles @ 62 mph
So it would seem the goal of a 75 mile range isn’t too far out of the ballpark, especially considering we’re targeting a lighter bike.
Rough napkin calculations? Give me a 10 – 11kWh pack and I’ll be happy. But let’s get legit and get some kWh/mile numbers from this.
- The Brammo Empulse, at an average of 88 miles with a 10.3kWh pack is going at .117 kWh/mile.
- The Zero SR, at an average of 108.5 miles with the base 11 kWh pack is at .10 kWh/mile. The SR with the Power tank is 133 miles with at 13.5 kWh pack, so also .10 kWh/mile.
- And the Energica Ego, at an average of 91 miles with 11.7 kWh, you get .129 kWh/mile. (I’m a little skeptical of that data point simply because the range numbers are quoted at such low speeds.)
So, for our bike, somewhere between 100 and 130 Wh/mile. Let’s say 120 (or .120 kWh/mile).
Conclusion? If we want 75 miles (average), we need something in the neighborhood of a 9 kWh pack, minimum, but more healthy would be 11 or so. Isn’t that what I said in the first place?
This is all good for a seat of the pants, drinkin’ ’round the fire idea, but stay tuned. We have some legit modeling going on behind the scenes, which should be fun to see how closely our napkin hit the mark.