Starting pointThe motor turns
OwnerMichael K Johnson
LocationCary, North Carolina United States map
Web/EmailWebPage email image
Vehicle2005 MTD Super Bronco
Motor Motenergy ME1004 Permanent Magnet DC
DrivetrainBelt-and-pulley "transmatic" CVT
Batteries5 Chevy Volt, 48.00 Volt, Lithium-Ion
Larger pack containing three 48V sections (and one unused 24V section) cantilevered over front wheels; Smaller pack containing two 48V sections mounted on shelf behind seat.

Initially used 4 Deka Intimidator 9A31, 12.00 Volt, Lead-Acid, AGM, which lasted several years but between reduced charge hold and moving from fescue to zoysia no longer supported mowing the whole lawn. (Now that set of batteries is being used as very ample support for my UPS.)

Will add 12V house power for AH meter.
System Voltage48 Volts
Hacked HP 48V datacenter power supply.

(Was previously Soneil SON4812SR 4-stage constant-current 6A 48V for the AGM batteries.)
InstrumentationClamp ammeter and cell phone GPS, when I feel like it.

Original ammeter in charging circuit to show rate of charge.

JLD-404 with isolated 12V power supply

500mv/500A shunt; JLD404AH amp-hour meter not yet installed (requires isolated 12V).
Top Speed6 MPH ( 9 KPH)
Acceleration0-6.2 mph in about 1 second
Range1/4-1/3 acre of mowing with typically less than 40% discharge
Seating Capacity1 adult
TiresFour original
Conversion TimeAbout six weekends, at least half of which was trying variations on filtered forced-air cooling
Conversion CostAbout $2300 initially not including $200 in unneeded purchases and $600 in tools I had been looking for an excuse to buy anyway. (I had projected $1500; much of the overrun was $1000 from the initial SLA batteries.) Then another $60 for the HP power supply, and $1000 for the recovered batteries from a totaled Chevy Volt.
Named after my grandfather, a skilled metalworker who built whatever he imagined. Also, after Frankenstein, resurrected by electricity ("resurrected" because the ICE was dumping raw gas on the muffler, resulting in scary clouds of blue smoke).

The "transmatic" CVT is not as efficient as a direct drive. I replaced the drive belts during the conversion, and engaging the transmission in neutral cost 40A. I later discovered that the replacement belts I used were neither OEM nor a direct replacement even though they were advertised as OEM; they had a deep V profile. Replacing the wrong belts with new correct MTD shallow-V profile belts reduced this cost to about 20-25A, saving me 15-20A for mowing the grass. Unfortunately, using the wrong drive belts did damage; they were sticky and caused some (I think minor) transmission damage; for a while, it was a bit "sticky" shifting gears. A fixed transmission would save only 10-15% of my total load during normal mowing vs. what I have now, though.

I can usually mow my entire yard in a single charge without exceeding 40% DoD even after converting from easy-mowing fescue to tough-mowing zoysia. I am mulching, which significantly increases the load. Going full speed over concrete uses 85-90A. Mowing grass while driving slowly uses 100-120A when the grass is not heavy. When the mower bogs down during mulching, just standing still and mulching can use 140-150A. Therefore, I have to go slower through heavy grass than I had to with the ICE.

I posted some "lessons learned" to EVDL: WebPage

code by jerry