Original Donor mowerParts - Ready for assemblyMotor installedAssembled A better look at the hood mount changesMaiden run
OwnerSean Bingham
LocationTracy, California United States map
Email email image
Vehicle1992 Sears Craftsman II 42
Conversion of a 12.5 HP IC, Sears Craftsman 42"
Riding Mower with 6 speed transaxle.
MotorMars ME0708 Permanent Magnet DC
Mars ME-0708 Permanent Magnet Pancake Brushed
motor. Etek-R equivalent.
48V, 8 hp continous - 15 hp peak.
Weight: 30 lbs.
DrivetrainStock 6 speed, belt driven transaxle
Controller Not required
Motor typically runs between 2000 and 2500 RPM,
which is equivalent to the ICE that was removed.
No need to throttle down. Can use the transaxle
to manage the speed.
Batteries4 Super Start 24DCMJ 12V Deep Cycle 140ah, 12.00 Volt, Lead-Acid, Flooded
Picked up some deep cycle batteries at
Kragen/O'Reilly. Will monitor their true
System Voltage48 Volts
ChargerSolar Renogy
Installed two Renogy RNG-100D panels for 200w
of solar on the shed. Used the 12v/24V charge
controller from the Renogy kit. This charges
4 12V Lead-Acid deep cycle batteries in
series. Using a 500w Black and Decker inverter
to plug in the mower charger and to charge my
other battery powered tools.
HeaterNoon day Sun.
DC/DC Converter None required
Not using the key start, so no need for to power
a contactor. Using 2 manual contactors (kill
switches) to a open and close the circuit.
Albright ED250.
InstrumentationFuel Gauge (voltage) for now.
Top Speed5 MPH ( 8 KPH)
Speed is regulated by the transaxle for the
1992 Craftsman mower. The manual lists the
speeds at:
1st gear = 1.1mph, 2nd gear = 1.4mph, 3rd gear
= 2.0mph, 4th gear = 3.0mph, 5th gear =
4.2mph, 6th gear = 5.0mph,
Reverse = 1.5mph
AccelerationStarts off easily in any gear and with blades
Range1st mow on 1/2 acre, mostly grass lot was
barely completed on the initial charge
(battery pack was not fully charged). Speeds
ranged from 2.0 to 4.2 mph. Grass was tall -
lots of rain. Will retest after full charge
and then some equalizing charges of the
individual batteries.
Watt Hours/MileNeed to put in an ammeter. Have a voltmeter
hooked up to look at general state of charge,
but need a way to look at current output to
optimize my operations.
EV Miles
Current:120 Miles (193 Kilometers)
    As of 10/25/2014
Seating Capacity1 adult
Curb Weight0
Not sure how much weight was taken out, but
added in about 250 lbs. of Motor, Battery and
TiresStandard Turf Saver tires
Conversion TimeTook about 3 months, mostly doing cardboard
prototypes and waiting for parts. Actual
conversion work time was 3 weekends.
Conversion CostWill put it actuals later, but about $1200
including shipping costs.
The adapter plate, pulley adapter and angle iron
battery frame added about $300 to the cost in
Additional FeaturesBattery Charger that I'm hooking into the Solar charge station is
a "Save A Battery" 2365-48 48V Battery charger/maintainer. I
replaced the previous Interacter 48V 5amp charger as it failed
after 18 months.

The solar charge station consists of 2 100w solar panels charging
4 12v Lead Acid deep cycle batteries, hooked up in series for 12v
output. I have a 500W inverter and a power strip to hook in other
battery chargers as well as the mower. I have the strip hooked
into a timer so that I'm charging the batteries when the sun is

Had been running a small Sunforce solar panel kit on the shed to
charge up the mower and other battery powered devices. In Sept
2014, I replaced this with a Renogy 200w starter kit consisting of
2 100w, 12v panels, plus z-bracket, and a 30A PWM controller. The
installation was quick and this does a much better job of keeping
all the batteries charged.

So after 4 full years, the mower is still running strong. With
better battery management, I'm getting better battery performance
from the new set of batteries, which are now 2 years old.
25-Oct-2014 - I've upgraded the solar charging station recently,
which will reduce the occasional need to plug into the wall to top
up the batteries. With better battery management, ie not
draining down the batteries too much, I now have 2 years on this
set of batteries. I get great mowing performance by splitting the
mowing over two days. The motor is just a work horse. Looking at
saving up to convert this to Lithium in order to save some weight.
That could cost $1200, so I'm in no hurry.

18-Jun-2013 - Little late on the update. I fried two of the four
batteries. Discharging too deep and recharging while hot did them
in. In September 2012, I changed the batteries to AGM style
batteries and have modified my mowing to doing the front one day
and the back yard the next day. This keeps the batteries from
cycling too deep and I get really good performance throughout the
entire mow.

Solar charging on the weak system I have is great for keeping a
charging station for my other battery powered yard tools, but
isn't quite good enough for the mower except in summer. I need
to add a panel or two to bump up the wattage.

07-Jun-2011 - Correction on the Solar Charger. It's actually
taking about 4 days to complete the charge. The charger unit
wants to stop charging too early. I need to get these batteries
up beyond 13V. Doesn't look like this base unit has any
adjustments I can make, so I'll probably look around for a
different charge controller. In any event, with a little tending,
I'm still solar charged.

02-Jun-2011 - Update - Now Solar Charged!
Was happy to find a relatively inexpensive solar panel kit on
Amazon for a Sunforce 12V 60 watt panel set, charge controller and
200w inverter. I've been able to move the mower off the patio
power outlet and into the back shed where I installed the solar
kit. I have been swapping the wiring from 48V serial to 12V
parallel on the batteries so that I can use the solar panel
charger directly. Seem to get a full charge in about a day. I
might buy a couple of deep cycle batteries and put those on the
solar charger, then just hook up the 48v battery charger to the
inverter. The 200w Inverter works fine with the 48V charger. The
Kit was $270, which is the lowest I've found. I didn't see a good
way to cobble together pieces for less cash.

With the warmer weather, I'm back to doing a full mow on a single
charge with capacity to spare. Having the mower in the shed will
help when the weather gets cold again.

Oh yes, I did replace the 10 year old tires with new ones that now
stay inflated. I keep the pressure up to about 20psi.

22-Mar-2011 Update -
Have used this as my primary mower for a full season. Late Spring
through Early Autumn, there has been no problem doing a complete
mow on a single charge. During winter, where we are in
California, the lawns do not go dormant and still need to be mowed
every 2 to 3 weeks depending upon the average temps and rainfall.
When overnight temps are in the 30s and daytime temps are low 50s,
the batteries cannot handle the full mow. I had to break out the
Gas Powered lawn tractor 2 times this year. I'll need it a third
time this week. So a couple of things to work out.
1) Method to warm up the batteries and their internals to an
acceptable operating temperature so that I can do the cold mowing.
2) Dealing with early spring tall and wet grass. Same as we
encountered after the initial build. The motor really draws down
the batteries when the cutting is very heavy. Haven't installed
the ammeter to measure the drain, so will make that my 2011 update

No new additions since the final build. Overall, very happy with
the quality of the speed, cutting and endurance for most of the
Will be replacing the tires so that they'll stay inflated each
week without me breaking out the fatboy tire pump.
Will be installing the Ammeter to get a better reading of amp per
hour requirements. I'm thinking of converting to LiFePO4
batteries to reduce the weigth and to improve the performance
until reaching the state of discharge. The Lead Batteries can sag
pretty much at the end of mowing long grass, which affects the
RPMs for the mower blades. Lithium is a much better curve. Will
need more accurate Amp/Hour specs for the wet and cold mows to
plan capacity. Converting the batteries will also mean a new
charger. The upgrade will likely cost about $800 unless I can
find some good deals.

05-Apr-2010 Update -
4th Mow on the conversion was very good, with plenty of power
left. The first 3 mows just barely had enough power left in the
packs to complete. A day after each full charge, the pack would
register 52.6 to 52.9 volts. At the end of my second mow, the
pack showed 45.5 volts. Whereas at the end of my 4th mow, the
pack showed 48.9 volts. Without the Ammeter, I can only guess at
the reason.
1) Mowed entirely in 4th gear. The cut speed was good, the grass
was long. Total cut time was about 5 minutes less.
2) Bagged instead of mulched this week. No real difference in
motor load on the high patches though.
3) I left the pack on the charger longer. Left it on for 20 hours
instead of 12. The charger shows complete after about 8 to 10
hours. I'll have to see if it continues a trickle charge.

In any event, if the performance is sustainable over the next 5
mows, I'll stop worrying about selecting another battery.

Original Post -
Received good inspiration off evalbum when viewing Carl Ervin's
Green Machine, also a 1992 Craftsman, David Eshbach's TEE (The
Electric Eshbach), and Wayne Riske's "'Ol Sparky".

Needed a Motor adapter plate to bolt the electric motor to the
chassis. The Chassis had a 6" hole where the ICE was mounted, but
the outer mounting holes for the Mars 0708 were 5 7/8" apart.
They had no metal to grab onto. Needed a Pulley adapter to deal
with the difference in diameter and length of the motor shaft.
The ICE had a 3 1/8" long shaft that was 1" in diameter. The Mars
0708 has a 7/8" diameter shaft that is 1 1/2".

Wanted all 4 batteries on the chassis, so fabricated a battery
rack from 1" angle iron. Needed to modify the hood since the
upper batteries would hit the hood at the stock angle. A bit of
'fitment' was required. Used some schedule 40 PVC to make new
mounts and stops for the hood.

Still need to add some screening to keep the motor compartment
clean. Also needs some serious lubrication and other cleanup.
The donor mower had been sitting outside, unused for about 2

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