Electric Drive Motor Retrofit

[JD-Beach]

I plan to call PT in Tazewell to discuss this opportunity and learn a bit more about the pump horsepower requirements. As I remember they are a little tight-lipped about their information, so, wish me luck!

I'll also call some EV conversion folks to see if they can help.

I'll keep you posted.

JD

 

[MossRoad]

I'm glad you understand the difficulty involved with 4 electric wheel motors on an articulated machine. A lot of people, myself included, do or did not understand how they act with movement of the machine until they see it in person, or really read a good description of it.

Just standing still, if you turn the steering wheel all the way to the left, for example, the two left side wheels roll TOWARDS each other while the two right side wheels roll AWAY from each other. Now add forward or reverse motion into the equation while turning and, well, good luck with figuring out how to apply the proper loads to each electric motor throughout that range of motion to prevent the tires from skidding. It will be a complicated and expensive beast.

One other note. At my last job of 30 years, I helped maintain and repair electric fork lifts, clamp trucks, bulldogs, lift table skid movers, robot skid wrappers and other battery operated production machinery. The batteries have to be maintained, even if you aren't using the machine. Just sitting around, even plugged into charger/maintainers, they'd lose water and degrade over time. They are expensive as heck to replace when they go bad, too. Granted, most of these were in use for a few hours every day, but many just sat there for weeks and months at a time as the newspaper industry declined. If we planned on using one of them that had been sitting, it was often the case that the machine was out of charge, down on water, corroded cable connections, leaking hydraulics, etc.... so we had to sometimes plan a few days in advance just to make sure the machine was operational.

I know this would be an interesting project, and if you have the time and means and it's your hobby, go for it. I find it extremely interesting and educational.

However, if it were me, I'd repower with a new gas engine for under $2K, treat the fuel with Stabil, shut off the fuel and run it till it stops. Then put a battery tender on it and come back in 6 months, check the guilds, turn on the fuel, fire it up and be on my way.

I just bought one battery for my Impala last week. It was well over a hundred bucks with only a two year warranty.

 

[RegL]

I’m going to be interested in how your project goes if you go ahead. I have 3 PT’s and I’ve had the same idea your talking about for years now but it never got any farther. When I brought it up here, I got lots of discouragement also, lol. The thing is, half the time I use a pt for jobs that only take a few minutes, like running to get a bucket of firewood. Being I have other tractors for the big time consuming jobs, the electric wouldn’t need that big of a battery pack.

 

[4570Man]

Without the complicated refit of electric drive motors using 3 separate electric motors on the hydro pumps would probably cut down on inefficiency. I think with such infrequent use battery upkeep will cost a fortune. I don’t imagine it’ll be any better than gasoline storage.

 

[Gravy]

Hey guys,

Maybe this hasn't been discussed yet: How long does this hypothetical electric PT need to run at a stretch? If it's fairly short bursts a few times a day, simply replacing the engine and gas tank with an electric motor and some random batteries might be all it takes. If it needs to run full-out for hours, it might be better to start with a clean sheet of paper and engineer a totally new machine.

And BTW, Prius batteries aren't a great choice for an all-electric machine. Prius is a hybrid that only runs on battery for low-speed operation and runs the internal combustion engine for highway speeds. The way I heard it, the vehicle was primarily designed to minimize smog emissions in stop-and-go traffic in crowded urban downtown conditions, like the middle of Tokyo or maybe Hong Kong. Good fuel mileage was almost a spin-off. Better to look at battery packs from wrecked Teslas, Nissan Leafs, or Chevy Volts, all of which depend mostly or totally on the electric drivetrain for propulsion. I don't have any experience myself, but I have it on good authority that Volt battery packs are made up of modular elements that are fairly easy to work with for homebrew projects, and can be bought for hundreds of dollars rather than thousands.

 

[quicksandfarmer]

I did some quick Googling of the Chevy Volt, the 2017 model. The battery packs cost over $3,000 new and can be had for maybe half that remanufactured. The battery weighs 405 lbs and is 5.5 feet long. It's a battery/gasoline hybrid. It's range is rated at 53 miles on battery only, on gasoline only it's rated at 42 mpg. So the battery pack delivers the energy of 1.2 gallons of gas.

Thinking about battery capacity in terms of gallons of gas is the best back-of-the-envelope way of looking at the problem. You might be challenged to match the effectiveness of the engineers at Chevy in terms of getting power out of the battery and to the wheels, but you're not going to beat them.

There is a direct trade-off between battery capacity and cost, weight, and size. Half the battery costs half as much, weighs half as much and is half as big, and lasts half as long. Likewise for one that's twice the size.

Here's the question: if you could only fill the tank once a day, what is the smallest fuel tank you could have without reducing the usefulness of the machine? Then figure out what size battery you need to equate to that.

 

[4570Man]

I think it’s the same or similar motor my Dixie chopper had. It’ll probably burn 1.5 gallons of gas in an hour. If you can only get that much energy from a 400 pound battery that isn’t promising.

 

[MossRoad]

Good points about comparing battery capacity to gasoline run-time.

For example, when running all out at 3600rpm, I can get just about 1 gallon per hour run time. Most of my uses are mowing, brush cutting, or pulling firewood long distances. Mowing the yard takes about 30 minutes, while brush cutting or pulling firewood I go for 4 hour shots non-stop. Plowing the driveway takes 20 minutes, but 5-10 of that is warming up the hydraulics at 1/3 throttle. The colder it is, the longer I warm it up.

Which brings up another issue.... cold hydraulics and the additional load that would put on the electric motor supply, and how long you'd have to run it to get things warmed up, etc... all based on ambient air temps.

Just one more thing to consider.

 

[herm0016]

could you rig up an accumulator on each hydraulic circuit and use a pressure switch to run the pumps? this way they will only be running when there is a pressure drop, actuating the circuit. for the drive it may not be all that efficient, but you wont be running the lift or pto all the time and those motors will be off when you are driving between places you are scooping mulch for example. a relatively small pump will run the loader and pto depending on your implements. I would be looking at your flow and pressure requirements, and electric hydraulic pumps that will meet them and stop thinking about the Hp of the gas motor. I Had a plan to convert a snow blower to electric with a 5 hp motor and a long nema 14-50 cord. We moved and i ended up with a larger blower on the tractor.

we also have a camper with a solar electric system and a Chevy Volt. The 1.2 gallons per charge thing is sorta right. the other side is, the gas engine is often only really making a few HP when you are cruising down the road at a constant speed and the gas engine is still running at some high rpm because of the gearing. the electric motor will only pull the amount of watts from the battery that it needs at any time to keep things spinning. It makes it hard to compare it quite like that.

 

[JD-Beach]

All good ideas and suggestions. I called Terry at Tazewell. You can imagine his response to the snake-oil I was proposing. Not to worry, I've been told my ideas are crazy by many folks over the years. I've also been looking at the many electric conversions on YouTube. There are many. I guy in Wisconsin named 2Jeffs1 replaced some old batteries in a Cushman cart with new Lithium Batteries. I understand the cost may be painful, but that appears to be the only way to go to get the size and weight down as well as reduce the maintenance.

One of the immediate details is the mounting of the motor to the pump, mounting plate, shaft size, etc. Does anyone know about the pump details? perhaps a replacement pump manufacturer and catalogue number?

I know of a few hydraulic machines that have a belt drive between the engine and the pump. This approach would not limit you to specific shaft sizes, spline details and length etc., and may result in an easier adaptation.

Just some early morning thoughts,
Thanks,
JD