How I converted a diesel engine tractor to electric for just $20,000

Jul 17, 2023

After the arrival of New Zealand’s first imported electric tractor last week, it transpires a Waikato handy man has converted his old engine tractor to electric for $20,000, to join an emerging electric tractor movement.

Hamilton lifestyle block owner Dougal Mair has recently converted an old David Brown 50 horsepower tractor to fully electric, and it took him about 18 months of his free time.

Working at Waikato University full-time, Mair has always had an interest in projects outside of work and converted two fuel engine scooters to electric, as well as a car over time.

This tiny tractor convert follows on from the arrival last week of Cromwell orchardist Mike Casey's first brand new electric - a Monarch imported from California.

READ MORE: * New Zealand's first electric tractor is here, but how does this line up with conventional farming? * All electric, fossil free farm down to entrepreneur thinking, 'under the hood' Kiwi ingenuity and a diesel tractor

Casey owns a cherry farm with 9300 trees, in Central Otago and plans to use the tractor’s fully automated capabilities for mulching, fruit disease detection, and spraying. Along with jobs that don’t require labour and worker skills.

His tractor is 40 horsepower, not much bigger than a ride-on lawnmower and with a price tag of $142,000.

Mair started his work before hearing of the Monarch import. He has a couple of horses on his 4-hectare block and says the electric addition to the farm just does what it needs to.

“I ripped the engine out and put in two electric motors, one for the transmission and the other runs the PTO and hydraulics.”

He put an $8000, 11.5 kilowatt lithium battery which can run for about 20 hours without charge “depending on what you use it for.”

So far Mair has been carting feed, topping grass and all the odd jobs on his block.

The IT specialist was raised on a Taranaki dairy farm so is well-placed to suggest his tractor cannot do the big jobs involved like carting hay and silage, but it can fill in the gaps for smaller, less weight-bearing jobs.

“It is working out really well. A $20k build, not including my time, and it's perfect for our needs.”

Mair started converting his tractor at the start of last year in his spare time and says the task was “relatively easy, if you know what you’re doing.”

He believes tractors like this, could be converted at low cost, and useful for the low yield jobs.

It isn’t the first of its ilk.

Before Casey (a software engineer) bought the Monarch, he gained his world first fossil free and all electric farming title when he first converted a tiny worn old diesel engine Iseki tractor two years ago.

His final step to becoming all electric was ringing in an engineer of a different kind, Christchurch’s Duncan Aitken, of Loxley Innovation, to convert it.

A combination of Casey’s entrepreneurial climate driven brain, and some plain old “Kiwi ingenuity under an engine hood” had this 39-year-old become a world leader.

The American Monarch, which is the 66th of its kind and the first to be exported by the company outside the United States, lifts a capacity weight of 750kg and runs at 540 RPM, which is the standard for a tractor this size.

The battery life is commercially sensitive.

It can be fully autonomous and once the computer or the ”brains” have learnt habits, it can complete the mundane tasks on its own and detect problems such as diseased fruit.

Couple that with the electrical capability, charging off the orchard’s Solar system for around $5, and it will work all day by itself.