Walk-Behind Tractor Converted To Electric

Walk-Behind Tractor Converted To Electric ENERGY Miscellaneous Converting a gas-powered walk-behind Planet Jr BP-1 tractor to battery power was easy and low cost for Reid Allaway He used an electric motor from an old battery-powered floor scrubber to replace the OEM 5 hp 1-cycle gas engine Doing so gives him precise control of infinitely variable speeds “The more I learn about electric drive systems the simpler it all seems and the variety of used motors available still astonishes me ” says Allaway “From an old floor scrubber to an electric scooter or a forklift or pallet truck to a crashed Nissan Leaf there are multitudes of parts donors out there for virtually any project ” Allaway says the floor scrubber motor was especially easy to work with because it is a permanent magnet DC motor wound for very low speed operation and reasonably high torque He explains that motors wound for low voltage battery applications are typically best suited to battery-electric projects “You’re better off scavenging parts from equipment that was originally battery-powered than adapting industrial DC motors designed for 90V operation ” says Allaway “AC drive systems for battery power are becoming more common but the high voltages and needs for careful motor characterization and programming make them overly challenging Don’t go and buy a scrap yard Prius thinking it’ll make a great electric tractor ” He explains that AC systems require a large inverter to make AC from the DC battery pack It has to vary frequency and current to achieve variable speed and torque DC motors simply require a controller that uses pulse width modulation to vary the voltage to the motor for variable speed To electrify the Planet Jr Allaway stripped away the gas engine and mounts fabricated a motor mount battery cradle covers for both and a chain guard He also assembled a lithium battery pack in an old ammunition can and modified an e-bike throttle for a trigger The motor controller was a cheap eBay find perfectly suited to the project “Cheap Chinese motor controllers are also available ” says Allaway “The control circuitry and wiring were dead simple though I did have to hide a tiny DC-DC converter in my top junction box to get a stable 5V signal for the trigger ” Allaway built the battery pack from 88 small cylindrical lithium iron phosphate cells They were assembled into blocks of 11 cells in parallel with 8 of the blocks connected in series to make a 24-volt pack that could store about 500 Wh of energy “I could have more storage capacity with newer cells but I had these on hand ” says Allaway “The pack is protected and balanced by a battery management system that I ordered online ” Allaway used a coulomb-counter shunt to evaluate the battery state of charge and displayed it on a monitor tucked into the end of the battery case He designed the battery pack to be removable allowing him to build multiple packs if he wants more run time “It’s like a handheld cordless tool but 10 or 15 times bigger ” says Allaway The Planet Jr ’s gas engine had been fitted with a planetary gear reducer on the output The engine drove a belt with the first stage reduction and a belt tensioner serving as a clutch The second stage reduction was a chain drive via a jackshaft from the belt drive It dropped power to the freewheeling main axle and provided a significant reduction in speed “I replaced the first stage belt with a #40 roller chain as I didn’t need the clutch mechanism ” says Allaway “As soon as I release the throttle trigger the electric motor spins down to rest ” In addition to precise variable speed and elimination of gas and oil Allaway points to low noise as another reason to go electric He compares a decent electric drive system to having hydrostatic performance and power but with more finesse at all speeds better control and next to no noise “We also find our employees learn to operate electric tools and vehicles and become proficient more quickly ” says Allaway Contact: FARM SHOW Followup Reid Allaway Tourne-Sol Co-operative Farm 1025 Chemin St-Dominique les Cedres Que Canada J7T 1P5 ph 450 452-4271; info@fermetournesol qc ca; www fermetournesol qc ca

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