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DET 193 - EV CONVERSION Blog

EV conversion classes: [index]

DAY seven: Oct 4th, 2008 - Saturday.

Day seven of the Santa Rosa Junior College Course -
DET-193. ELECTRIC VEHICLE CONVERSION.

The class gathered for the seventh session of the course, taught by Peter Oliver of Make Mine Electric.

Chris Jones, President North Bay Electric Auto Association (and his kids, Trever and Megan) joined the class to talk about the differing kinds of battery, their chemistry - and how it affects the price and decision making process. With many questions and much discussion the presentation took close to 3 hours. It seems like it needs to be its own course at the SRJC. See a .pdf version of his presentation.

What is a batery: Basically a black box.

(Conventional Theory as per Benjamin Franklin):

During Charge, current flows to the "anode +" through the electrolye causing a chemical reaction in which ions move into the "cathode -" which causea expansion of the battery pack. 20% can be lost to heat in the charger and the battery.

During Discharge - curent flows in reverse going from the battery to the motor (Load), again enery is lost to heat all down the way.

EV Battery Requirements: EV applications are one of the most strenuous uses for a battery.

Safe, High power, High capacity, Small and light, Large format, Long life, Low Overall Cost.

High Power: Watt = vols x amps
Ohms law V= IR [V= volts, I= current/amps, R=resistence.
Internal resistence is an important element to consider
Rated in terms of "C" - the ration between max current and current draw to drain battery in on hour.

Key:
How fast can current be drawn for how long

High Capacity:
Energy = watts x hours = V x Amp-hours.
Watt-hours reduced with higher dischare current du to internal Resisance heating loss.
Amp-Hours can be significantly reduced to Peukert Effect.
Amp-House can be reduced in cold weather: Lead acid 50% at freezing, Li still 80-90% at freezing.

Small and light:
Specific Power, Specific Energy, Power density, Energy Density:These will determine wieght and volume of the battery pack needed to fit a given vehicle.

Large format: Less connections, less soldering within each battery pack - less possibility of breakdowns.

Long life: Battery Killers: Temp, Cycling and time.
Key: True cost lies in number of cycles e.g. Lead acid give 400 cycles vs Lithium Iron Phosphate's 1000+ cycles.

Battery Management: each battery needs to be balanced to its requirements to avoid over or undercharging individally.For Safety knowing temp of each battery is most desirable. Each battery has minor individual internal resistances, which has a cumulative effect.

Much more was said, but see his presentation for more information.

After a lunch break the class got back to work on the cars, plus a new project of electrifying a 1979 Harly Davidson Motor bike.

End of Day Status reports (To come)

Michelle's Toyota:

End of day Status:
Attention was still being focused on attempting to revive her battery pack to avoid the epxense of total replacement it at all possible.

>>> cont next column >>>

<<< Back to day Six

Above: Chris Jones and his young and (usually) enthusiastic assistant teachers.
Below: Close-up of the Harley Insignia on the new project bike.

<<< from previos column
Ed's VW:
End of day Status:
Relay panel completed, controller and charger installed. Front battery rack was painted ready for installation, rear battery box completed, a start was made on the preparation of battery to battery jumper cables. Estimated 2 weeks works left on this vehicle

Kyle and Kara's 1979 Harley:
Their object is to maintain the look of the bike as much as possible by such things as keeping he tank to hold he controller and charger, building battery boxes in "V" shape over the motor, to keep the look of the original "V" cylinders
End of day Status:
All fluids were removed, seat and exhaust pipes were removed. Plans are to use excited "DC" motor.

Don's Plymouth Horizon:
Non-EV elements of the project have nearly all been addressed.

End of day Status:
Decisions were made on which batteries to use (LiFeP04) which informs the design of the new battery packs. Motor is being refurbished by the Electric Motor class.

EV Motor cycle.:

End of day Status:

No team worked on the Thundermotor's electric bike this week.

Wooden Speedster Mock-up.

End of day Status:

An Aluminium "L" bar was drilled and mock up switches were installed. The mock-up had been driven over at some during the week and had been moved out of the way. So this was done again at the end of the day.

On to day eight >>>

More photos of Day seven.

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