From the testing, it was clear the tractor will be a productive tool around the grounds. We decided an investment in the purpose-built Motenergy would be worthwhile. The 48 V, permanent-magnet DC motor with a 1-inch shaft will have enough power for the stacked pulley that also drives the mower deck. However, the bigger motor will work well within its load range and will heat up less, and will be more efficient.
Switching the two motors was a matter of unbolting the first one and using the same mounting plate for the new motor. Both motors have a standard NEMA C bolt pattern, so the holes matched up perfectly—and the cable attachment was also a match. Then all we needed to do was remount the mower deck.
This is a great example of building a balanced system. When the tractor had the small motor, small batteries, and a relatively light load, it provided good power and range. Once we increased the motor size, we could add more load, like the mower deck. However, the batteries were not up to the task. Monitoring how much “mowing range” the original batteries provided gave us an understanding for how we’d need to upgrade. The smaller batteries let us mow just barely a quarter-acre, if they had a full charge and we were careful not to waste energy. Increasing the battery capacity to four quality small, flooded lead-acid automotive batteries in the 40 to 60 Ah range was necessary to get an acceptable mowing range of our quarter-acre lawn, with a little extra for insurance. A nearby salvage yard sells used batteries for $35 each. Even better would be to use 12 V deep-cycle batteries, similar to those intended for golf carts.
What will come after that? Adding function is simply a matter of adding another motor, so there are many options: a power take-off, hydraulics, etc. For now, though, it looks like the resident teenager has a lawn to mow!
Ted Dillard has been an avid gardener since childhood and is an evangelist for all things electric. He writes The Electric Chronicles (devoted to two-wheeled electric vehicles), and is the author of ...from Fossils to Flux, a basic guide to building an electric motorcycle. When he’s not in his garden or in his shop working on his next electric project, he can be found at evmc2.com.
Suppliers (Parts & Kits):
Electric Motorsport • electricmotorsport.com
EV Drives • evdrives.com
Motenergy • motenergy.com • Permanent magnet motor
Thunderstruck Motors • thunderstruck-ev.com