# planning UTV electric conversion



## pcman (Oct 7, 2011)

Your skill level with auto mechanics and fabrication: *auto mechanic, welder, electrician, good diy/fab skills*
The range you are hoping to get (how many miles/charge): *really 3-4 hours run time is what we need its only a small farm 10 acres so id guess less than 10km a day *
What level of performance you are hoping to get: *offroad towing a 1100kg trailer speed not really a issue *
How much money you are willing to put into your project: *cheap and reliable dont go together so willing to spend what it costs to make us happy 


hey all ive been given the task of looking into converting my uncles utv to electric , curently powered by a 20kw- 300cc engine 

however the engine is stuffed and he is off the grid using solar and wind turbine so he thought a electric conversion makes sense

now ive looked around but really cant get my head around all of this kw-hp-watts 

its mainly used to tow a water trailer around to fill water troughs and feed the animals, so it still needs to do this but speed isnt really a issue 

really i guess what im asking is what size motor would i use , it has a standard rear car style diff with forward/neutral/reverse so i was hoping i could just direct drive this 

cheers
casey






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## madderscience (Jun 28, 2008)

UTVs like one of these?

http://www.utvguide.net/utv_models.htm

There are actually a few electric UTV models out there already, such as this one:

http://www.polarisindustries.com/en...tility-Vehicles/RANGER-EV/Pages/Overview.aspx

So even if you didn't want to buy one of those, You could get a good idea of the sort of performance you would be able to get out of yours if you were to put a similar drivetrain in it. You might also seek out some of the owners of such vehicles and ask them what they get out of them.

1 horsepower is equivalent to 746 watts, so a 20kw gas engine is about 27hp, but this is probably a peak HP value. Electric motors are typically rated for continuous duty. Motor controllers also have a continuous duty but also often give a peak rating. For continuous HP an electric motor in the 10hp (8kw) continuous range would probably be the minimum advisable as it would still be able to belt out a similar 20kw intermittently. For a controller, you would need to pick on with continuous duty rating the same or better than the motor, and peak power around 20kw.

You will have the torque advantage of the electric motor that you don't get with the engine, in that you get maximum torque at 0 rpm. However, you may still want the overall gear ratio to be higher with the motor than with the gas engine. Electric motors like to run at higher RPMs. So if you do consider direct drive, use the highest ratio differential you can get. An overall gear ratio around 12 to 1 might be adviseable in such a vehicle. (direct drive in roadgoing EVs is typically in the range of 4:1 to 10:1 depending on many factors, but the tire diameter is also much larger for roadgoing cars)

Look very seriously at some of the HPGC / Curtis AC drives as they were originally designed for smaller vehicles and are available in all kinds of horsepower and battery voltage ranges. I would personally shoot for one of the 72v systems. 

As for battery capacity you are going to need to figure out how much energy you actually use. 10km may not be that much distance but if you are slogging through mud with a 1110kg trailer for that whole distance, you may still be using a lot of juice. One way to estimate this would be to figure out how much gasoline you burn in a typical day, and try to estimate the equivalent electrical energy you would need. A place to start might be:

(gallons burned * 0.25) * 33.6KwH

Basically, I am assuming that an electric drivetrain is four times as efficient as a gasoline drivetrain, so this conversion would yield the amount of battery capacity an electric drivetrain would need to do the same work. For example, if you burn 2 gallons of fuel in a day, you would need 16kwH of battery capacity to do the same work. Note that the 1/4 number is realistic for roadgoing cars, it may not be the right ratio for a UTV. Smaller gasoline engines are often less efficient than automobile engines, and you can throw out all gasoline burned idling the engine from your calculation. Basically, you will have to do some research on it. 

Finally, if your vehicle has a canopy and you live in a sunny area then in the course of a day, a 200W solar panel on the roof of the vehicle might be able to provide a significant portion of the day's operating power though unlikely all of it. Still, might be worth some quality math time to figure out what the benefit might be.

Good luck.


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## major (Apr 4, 2008)

pcman said:


> The range you are hoping to get (how many miles/charge): *really 3-4 hours run time is what we need its only a small farm 10 acres so id guess less than 10km a day *
> What level of performance you are hoping to get: *offroad towing a 1100kg trailer speed not really a issue *
> How much money you are willing to put into your project: *cheap and reliable dont go together so willing to spend what it costs to make us happy *
> 
> ...


Hi pc,

I've been involved with electric IUV (Industrial Utility Vehicles). Here is one I use around my 2 acre spread. 










It was a ground up build. Uses 48 volts. Pb-Acid, 4, 12V, about 100 Ah, IIRC. Been years since I've been into the battery compartment. I'm sure batteries are less than half capacity anymore, but I don't need many miles. When new, I did some distance testing around the country roads, unloaded, flat and got bored after like 10 miles. It is not geared quite right so has a top speed of like 30 mph. I have controller set with Hi and Lo speed switch, so in the yard, I can keep it below 6 or 7. Never had any problem towing, see photo. About half to 2/3 rick of hardwood. Mostly flat around here, slight grade in front yard. Never a problem.

It uses a 6.6" diameter golf cart motor, sep-ex, with regen, Curtis controller, 400A limit. The motor is totally enclosed, smallest of the golf cart varieties, so likely rated at 2 hp (one hour). Would peak at about 45V * 400A = 18kW input, so about 18 hp motor shaft. I don't think I ever see that, maybe starting out, motor will hit it, but ammeter for battery rarely goes to 100A. With that load of wood today, creeping along as not to spill it, I was drawing 40 or 50 amps (battery), so about 2 to 2.5 hp. All pneumatic tires on vehicle and trailer. Fairly soft turf. Level.

It is direct drive. Similar axel as found on a commercial mower. Can't remember the ratio, but isn't high enough, hence too high max mph, but still no trouble towing.

Also, see in the attached photos my other etractor. 35-40 year old Sears. Converted 15 years ago. It also pulls strong. Will pull that same trailer of firewood. No problem. It is belt drive with a 3/4 hp floor sweeper motor. 3 speed tranny with reverse. 2nd is about the only gear I use (& reverse). Ran it for years with 4 small Pb-Acid. Recently installed Li-Poly I came across. Have a $30 tractor with a $2000 battery  WTH.

You don't need huge electrical hp or really big motor. Depends a bit on your hills and travel surface. Direct drive with proper ratio should do. Lithium batteries are great, but I'd suggest golf cart flooded for starters. Best $/Wh value and chargers, and motors and controllers should be reasonable at 48 volt. Might even look into a second hand electric golf cart and see how it does out of the box.

Cheers,

major


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