LeftRightFrontBackBatteriesBike FrameBattery RackAssembly
OwnerStewart Harding
Owner's Other EV1988 Kawasaki EX250 R2.0
LocationVictoria, British Columbia Canada map
Email email image
Vehicle1988 Kawasaki EX250
MotorMars ME0709 Series Wound DC
Generates a bit more heat than I was
expecting. Wondering if I should have
gone with the PMG132.
June 2011 update: over the winter when
the bike was stored the brushes seized
up, so that in the spring there was
heavy arcing. There was no permanent
damage to the commutator. I called Mars electric and they quickly sent me a replacement brush assembly. The bike
was stored indoors. The brushes seemed
to have swelled. No corrosion....They
are apparently working on a new brush
assembly design. I'm happy that Mars
provides such good customer support!
Drivetrain420 chain, 70 teeth rear, 16 teeth
front. #4 wire for all high current
circuits (considering upgrading to #2
from the controller to the motor) - as
these leads seem to get the warmest
after a spirited ride.
ControllerAlltrax 7234
300 Amp. This units is great! Generates very little heat, built very well, and quite small. The only thing that would be better (very minor issue) is a torque (amps)controlled speed control. This unit appears to be controlling output voltage based on throttle setting - applying up to 300amps to get you to this voltage (speed). It takes some getting used to when riding the twisties as throttle control (which determines the lean angle and turning radius) is completely different than from a gas engine. I suppose the lack of engine braking also doesn't help. When riding for fun (not concerned about range) I find myself hard on the brakes much more than when this bike was gas powered...
Batteries6 B and B EV50-12, 12.00 Volt, Lead-Acid, AGM
50 Ah. Managed to squeeze them all in.
Needed to remove the bottom faring.
1st option was the 35Ah which would
have easily fit and kept the overall
weight to same as or slightly less than stock. Glad I went with the larger batteries - even with the weight (acceleration) penalty - for the additional range.

Seriously thought about and almost went with TS-LFP60 lithium...but seemed much more complicated requiring a battery management system, and those systems that ran without seemed to have reliability issues...As with everyone - saving this upgrade for the (hopefully near) future.
System Voltage72 Volts
ChargerSoneil 2412SRF
6 amp, 24 volt, 3 units across 3 sets
of 2 batteries in series. Note that not all Soneils can be connected in a
series string like this...
June 2011 update: these chargers are
now mounted inside the gas tank. I've
been extremely impressed with these
chargers. The batteries have remained
in perfect balance, and the performance now (aprox 3000km after conversion) is the same as it was when new. The bike sat over the winter and I plugged it in for a day every month or so to keep the batteries fully charged.
HeaterM/C gear. Heated grips will come with the cooler weather.
DC/DC ConverterSevcon 622/11086
300 watts at 13 volts, fully isolated. 72-80 volt nominal input. Very happy with this unit. Seems to operate just fine all the way down to 40ish volts. Produces very little heat.
InstrumentationEverything as stock except for tach,
oil pressure and temperature gauge.
Plans to convert the tach to an Amp
gauge. Also plans to put the temp
sensor on the motor - as it seems to
generate the most heat in the system.
Top Speed60 MPH (96 KPH)
Pulls quite good to 50, after that, tapers off to 55 or 60 depending on riding position, incline, head wind, state of charge of the batteries.
AccelerationConstant acceleration 0-50. aprox 6 seconds.
Range25 Miles (40 Kilometers)
Not fully tested yet (want to be kind
to the new SLA's). Calculations show
that it should be dependent on cruising speed. 30 mi @ 30 mi/hr, 20 mi @ 45 mi/ hr, 15mi @ 55 mi/hr to 70% DOD.
June 2011 update: (after aprox
3000km/2000mi) I commute about 1/2 the
days in the summer a distance of 22
miles both ways. 1/2 this commute is on the freeway at top speed. Chargers put back in 30Ah after this round trip. Haven't taken it much farther than this. Still has very decent performance at this point (4 mph lower top speed then when fully charged).
Watt Hours/MileJune 2011 update: my 22mi commute requires 30Ah. The chargers put back in 6amps and require around 600Watts (at 120V) to do so. Working out the math this would be 136Whr/mile.
EV Miles
Start:31,875 Miles (51,286 Kilometers)
Current:33,875 Miles (54,504 Kilometers)
Total:2,000 Miles (3,218 Kilometers)
Seating Capacity1 'normal sized' (6ft 185lbs) person, or two smaller people. (It is a small
Curb Weight460 Pounds (209 Kilograms)
Original ~425lbs. About 50lbs heavier than full wet weight (full tank of gas) stock.
June 2011 update: with the chargers and a 25ft extension cord mounted in the gas tank, weight is now ~460lbs.
TiresNothing special. Standard ones it came
with inflated to max pressure (42/44)
June 2011 update: This winter I
replaced the old tires which were 16-
100/90 front and 16-130/90 rear, with
the correct stock size which is 16-
100/80 front and 16-130/80 rear. This
size is not as common, but I found a
set of Pirelli Diablo Scooter tires
that were perfect. These tires are a
lighter construction (2ply) and are
much softer and incredibly sticky wet
and dry. The handling of the bike is
also slightly better with the smaller
profile. Top speed was reduced very
slightly so I went to a 17T motor
sprocket to compensate. I'm very
pleased with these tires (except that
they say 'Scooter' in large letters on
the side :) )
Conversion Time6 months spare time
Conversion Cost$2500 in parts
Additional Features'Neutral' with kick stand and engine kill switch lockout. Push to 'start'. Neutral light as well. Throttle disable on controller if 'started' with throttle applied. Works well at avoiding accidental power to the motor...
I'm very happy with the outcome. Acceleration is slow for m/c standards, but still much quicker than the normal flow of traffic. Drive train is quite torquey, can easily spin the rear wheel when not seated on the bike. It's a bit heavier than I expected but the center of gravity is low. With upgraded springs in the front forks (0.75kg/mm rate) handling is just like stock. No more bottoming under hard braking.
June 2011 update: after 2000 miles and some minor
improvements this bike is working better than ever. I'm very pleased with it.

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