I am thinking of undertaking a VW Beetle electric car conversion. The mid 60's cars are not too expensive, and weigh around 1600 lbs. I figure the engine is 400 lbs or so of that. High level plan :) 6 big batteries (85 A-H)and 20HP 3-phase motor. The new power train including batteries would weigh around 600 lbs to there is some weight gain. Running some numbers looks like 220 amps @ 72 VDC yields 20HP. Does that sound reasonable?
Near as I can tell run time at 220 amps is about 2 hours if I got the calcs right. As my commute is only 20 miles round trip this seems sufficient.
WRT transmission ... these cars had a transaxle with the rear wheels driven off floating shafts off spiral ring-gear. While there would be some mechanical losses retaining the ring-gear is seems the simplest approach - basically lose the engine & transmission and feed power direct to ring gear. The rear drive ratio is 4.375:1. I ran some numbers again and the gas engine was spinning around 3700 rpm at maximum speed of 72 mph (116 kmh). My question is how does this translate to these electric motors, is the rear drive ratio low enough? Or retain the transmission and lock in 2nd (2.06:1, total reduction 9:1) or 3rd (1.32:1, total 5.775)? I would prefer to get rid of the transmission to avoid more mechanical losses ... oops forgot that rolling radius of stock tires is 2.02m yielding wheel rotation rate of 957 rpm.
Any recommendations for component suppliers in Bellevue, WA?
Hi, Jarmo - This is way too much math for me, my friend. I don't know if you noticed, but this is the remedial class; )
Since you asked my opinion, though, 72 volts is probably sufficient. 96 volts might be better. It's always a juggling act between handling (weight, battery placement options) and performance (acceleration, braking).
As for a Bellevue parts supplier? I'm not sure where locals are getting their EV parts now. I would check with Seattle EVA.