DAY TWO: Aug 30, 2008 - Saturday.
Day two of the Santa Rosa Junior College Course -
DET-193. ELECTRIC VEHICLE CONVERSION.
18 people gathered to for the second session of this new course, taught by Peter Oliver of Make Mine Electric.
Getting down to details:
Working out the roll-out - the distance your car's tire travels in one revolution. Pete showed an Excel Spread sheet that calculated the optimum rpm of the motor at a given speed, given the final drive ratio. My Nissan goes 69 inches per turn = ie.918 tire revolutions per mile. At 60mph that makes 64,400 revolutions per hour or 1,073 rpm. So taking a final drive ration of say 4.2 I'd want a motor that does best at about 4,300 rpm.
Checking out the various motor makers (see links on first page) we then work out what engine within our budget would work.
The class also discussed the advantages of transmissions vs. direct drive ungeared - Accelaration vs top speed being the major compromise to be decided in an un-geared single speed drive system.
Also discussed AC vs DC. To-date most conversions have been using DC engines, but as Peter spoke to many, they nearly all said they would go to AC next time.
AC: longer power curves, simpler, easier regenative braking and more efficient, better performance, smoother, more predictable, no brushes, no maintenance.
More expensive - not many on he second hand market yet.
DC's can "default" in the ON position.
After the mid morning break
Ed Ristad, owner of the Red Rabbit in the shop spoke to the class. He ran an auto repair shop in Sonoma until retiring 15 years ago. Started taking Alt. fuels class done by Mark at SRJC (see previous blog entry) last year and was blown away by the new possibilities. Mark asked if anybody wanted to build and EV and Ed spoke up. North Bay EV club helped him out.
continued, next column >>>
.He chose to make the VW Rabbit with an AC motor. Rabbit is a common conversion with many off-the shelf parts to cope with addition battery weight etc. (See photos of his Rabbit taken at last week's class)
Voice of experience: Mark every wire, and dismantle the ICE (Internal Combution Engine
) VERY CAREFULLY and systematically.
Weigh the car in total and at each wheel. Take note of curb weight and Gross weight (see Public Scales in CA) and try to keep the same distribution as the motr and batteries are installed.
For each bracket to make or weld, allow 4 hours.
Ed also chose the Azure motor independantly of Peter (Peter comment that he was also attracted to it because of the reports that Mexico City bought a thousand to convert Government vehicles to EVs.)
Batteries: Various Decisions to make:
Lead acid of various kinds. Ed chose the the absorbed "glass matt" gel cell (AGM) as they can discharge and recharge quickly and hold a charge well.
Lithium Ion Batteries: Still expensive, but prices dropping quickly, as prodctions ramps up.
Also spoke of MIT's Solar catalyst system for creating Hydrogen and oxygen during the day to be stored and recombined in a fuel cell at night to power homes, and recharge our EVs.
Final Advice - keep away from AUTO Transmissions - absorb too much power.
The class was then joined by Julian Darley of the Post Carbon Institute whose mission to educate the the world to get off Carbon based fuel as soon as possible. The intstitue Runs the Vancouver EV car share program in Sebastapol (Solarcarshare.org), powered by Solar Panel Electric generation. Believes car sharing one of the single most powerful tool for moving away from carbon based fuels.
(Check Eestore - Ultra capacitor technology and the ScienceCentral Archive on upcoming Capacitor developments.)
Retrofitting existing cars eliminates the ecological cost of the production of new vehicles which we often leave out of the entire equation.