Retro electro Troy-Bilt Rototiller conversion

August 5, 2015 
by Jack Anderson

In spring 2015, Jack Anderson and Randy Brooks were traveling to check on electric car chargers they helped get installed. As they drove, Jack mentioned he was looking for a rototiller to convert to battery electric. There are several examples on the web of tillers converted to corded electric, but no examples of one converted to battery electric.

Randy said his dad had a Troy-Bilt Horse rototiller he had used a few times and then gave to his sister over 10 years ago. A quick phone call and they learned the tiller was still in the shed where Randy left it, and his sister was glad to have someone use it. One more phone call was in order, however. Charlene, Jack’s wife, would need to agree the pair of intrepid “converters” could spend more than the cost of a brand new rototiller!

So Jack and Randy picked up the tiller – a 1984 Troy-Bilt Horse model with electric start gas engine. All the pieces were intact, although the paint was faded, the decals were gone and the tires were cracked. Still, it had potential.

After hauling the tiller to Randy’s house, the first step was to see if the shaft on a PMG 132 perm pancake electric motor – that Randy had left over from another project – would fit the tiller. Turned out it fit perfectly. Next Randy and Jack stripped all the parts off the tiller and Jack took it to Rowe’s Tractor in East Wenatchee to have a small problem in the drive train fixed and to purchase a new set of tines, as the old ones were really beat up.

Randy also had a 48 volt Alltrax motor controller left over from the same previous project, so the next question was if the motor and controller would work together and turn the tiller drive train. They reassembled the tiller, with the new tines, and made up a prototype electronics cluster and wired it to the motor. Then they connected a 48v battery bank Jack had to see if the motor worked and turned in the right direction.

The motor worked, but turned in the wrong direction, so they reversed the positive and negative cables, and, wahoo!, it turned in the right direction!

The next step was to determine if the tiller would till and not bog down the motor, plus check how many amps it used so they could estimate the battery bank size needed for at least one hour of tilling. Randy tested the amp draw with a clamp-on meter and determined a 50 amp hour battery bank would be adequate.

They checked out lithium battery banks, but due to the high price tag they settled on four Deka 50 amp hour sealed gel batteries.

When the batteries arrived they strapped the battery bank onto an electric Gorilla ATV and took the tiller to some untilled, hard-packed ground to see if it would “till”. It did! Randy measured the maximum current draw at 10 to 15 amps, which means the battery bank would support an hour or more of use while not drawing the batteries below 50 percent state of charge (best for reasonable battery life).

A battery rack and electronics cluster enclosure was fabricated by Irish Iron, a local metal shop in Chelan. In the meantime, they painted it (with real Troy-Bilt red paint!), reassembled the tiller and bought new tires. The electrical parts were painted green and, after mounting the battery rack and electronics enclosure on the reassembled tiller, it looks really good!

Jack found some original decals (don’t you just love the internet?) and put them on the tine cover.

Randy was concerned about dust and debris getting in the motor, so he fabricated a motor cover from a five-gallon plastic bucket. They’ll see if there are any issues with heat buildup during operation. Jack contacted a local sign maker, Chelan Printing, to make custom decals for the motor cover and electronics cover. A 48 volt, 5 amp battery charger was purchased and set for gel battery specifications, so the battery bank can be safely charged.

The final product is ready to go and show!

This was a really fun project. Thanks to Jack and Charlene Anderson for funding it and to Randy Brooks for donating small left over components and hours of labor.