InstrumentsLeft SideRight SideFrontRear
OwnerStewart Harding
Owner's Other EV1988 Kawasaki EX250
LocationVictoria, British Columbia Canada map
Email email image
Vehicle1988 Kawasaki EX250
This is the 2nd revision of this motorcycle conversion. See this page for the 1st conversion with AGM batteries:
MotorMars ME0709 Series Wound DC
Original motor, on its 2nd set of brushes. The brushed motor is the weak link in the system. It can get quite warm if driven hard at lower speeds (without sufficient air cooling).
Drivetrain420 chain, 70 teeth rear sprocket, 17 teeth front sprocket. #2 wire for all high current connections.
ControllerAlltrax 7234
300 Amp unit. Original controller. Rock solid. Generates very little heat.
Batteries24 Thunder Sky 60Ah, 3.20 Volt, Lithium Iron Phosphate
Sinopoly (I believe used to be Thunder
Sky) prismatic Cells. 87.6 Volts at full
charge, ~72-76 volts under load.

EV Power BMS system (24 cell modules +
mcu-Micro-08) with custom edited picaxe
System Voltage77 Volts
ChargerSoneil 2412SRF
With max output voltage adjusted up to 29.2 volts (3.65 volts per cell). 3 units
connected in series. 6 Amps output current to the battery.
HeaterOxford Heated Grips - extremely nice in the cold weather. Aprox 40 watts load at full power. Impact on range is negligible (aprox -1%).
DC/DC ConverterSevcon 622/11086
300 Watts, 13 Volts, output fully isolated from the high voltage (main) battery circuit.
InstrumentationCycle Analyst DC power meter, Amp hour meter and Speedometer.
Top Speed60 MPH (96 KPH)
The bike lost ~100lbs from the previous
revision and the system voltage is about
~10 volts higher under full load.

Note: This speed is reported by the cycle analyst, and confirmed with GPS. The indicated speed from the stock speedo is ~110 km/hr or 69mph.
AccelerationMuch more spirited acceleration than before - feels similar to stock up to 55mph and tapers off up to 60mph. Need to take some data with GPS to get an exact time.

This level of acceleration is on-tap, all the time, with instant throttle response, no gear changing, and the delivery is extremely smooth and quiet, making the ride quite fun.
Range50 Miles (80 Kilometers)
This is the fully tested range, under
mixed driving conditions (some highway, come city, and some back roads), until the BMS kicked in (one of the cells fell below 2.5 volts under load).
Watt Hours/Mile120 Wh/Mile
The fully depleted battery requires 10 hours to recharge. The chargers require ~600 watts from the 115VAC while recharging. 6000Whr/50miles = 120 Whr/mile.
EV Miles
Start:34,688 Miles (55,812 Kilometers)
Current:35,138 Miles (56,537 Kilometers)
Total:450 Miles (724 Kilometers)
    As of 2/9/2014
Seating Capacity2 smaller adults
Curb Weight360 Pounds (163 Kilograms)
A few pounds less than the stock 'wet' weight.
Tires16-100/80 front and 16-130/80 rear Pirelli Diablo Scooter tires inflated to ~30psi.
Conversion Time6 months spare time (in addition to the
original 6 months)
Conversion CostOriginal conversion cost of $2500 (subtract $700 for the lead acid batteries), plus $2200 for the lithium batteries, $300 for the BMS system, $150 for the cycle analyst, $100 for the heated grips, $200 for misc => total ~ $4800
Additional FeaturesLED mirror lights and 'running lights' added to the turning
indicators for increased road presence. Much brighter Brake
lights (extra bulbs put in the otherwise unused in North
America red turning indicator lenses next to the stock brake
lights to make it more visible). 'Neutral' state integrated
with the kick stand and start button (so the throttle is not
live without 'starting' it first - and it wont 'start' with the kickstand down).
The electrical complexity is much higher than before,
especially with the lithium battery stack. Each cell is
connected to the next with a bus bar system. There's a cell
module on each cell for the BMS. The BMS system is integrated with the controller and the chargers to provide safe cut out when needed. The addition of the Cycle analyst, heated grips, additional brake lights, additional LED driving lights, and running lights is also all added to the mix.

The lithium batteries are not only 1/2 the weight of the AGM
lead acid batteries, but also take up 5/6th the space, so I
now have an extra storage compartment under the seat, where
one of the AGM batteries used to be.

Handling of the bike is more lively. I kept the stiffer
springs from before. With the tires inflated to the standard
pressure the ride is firm but not uncomfortable.

Performance of the bike is much improved. It can go 50 miles
at highway speeds, and the acceleration and top speed remain
the same all the way to around 45 miles. Also no reduction in top speed with cooler weather.

I'm extremely pleased with the upgrade to Lithium Batteries. It has completely transformed the bike.

The only other modification I'd like to do, is to go to an AC brushless motor/controller.

code by jerry