# Electric 6x6 skid steer ATV



## YourSolutions (Jul 21, 2014)

I've acquired a homemade 6x6 skid steer ATV that I would like to put an electric drive system in. The ICE and transmission were removed by the previous owner and are not available. It does have brakes on each wheel.

I want to use the 6x6 as a tractor for a small one hectare (2.5 arces) orchard. Max gross weight will be about 1200kg (2645bls), max range 5km (3 miles) @ 10km/h (6ml/h). I haven't weighed the vehicle yet but guesstimate it will be about 400-500kg with drive system and batteries installed. Tires are 650mm (25.6") diameter. Most demanding job will probably be towing a small cultivator, otherwise it will just be hauling loads round.

I have all the required fabrication and electrical/electronics skills plus tools to do the work, however this will be my first EV project. My budget is only $1500-2000USD not including batteries since I could do an ICE drive system for less than that (although it would be used parts). I'm willing to shell out for LiFePo4 batteries to run it.

Looking at others conversions on this forum for tractors etc. (such as JRP3's AMPhibian and major's tractors), using PStechPaul's VehiclePower spreadsheet and other torque calculations I think need about 10HP (5 to each side). 

So I will need two electric motors in the 4-5Kw range and 60-100A/h batteries with two controllers, each capable of 200-250AMPs. Does this sound about right?

If the above assumptions are correct my next problem is locating the parts with in budget. This is going to be very difficult since I live in New Zealand and don't have access to all the used parts available in the US (shipping is expensive).

It would be wonderful to go with AC motors and controllers for this to enable simple forward/reverse skid turn control but that is way out of the budget scope. 

- What type of DC motors and controllers can I use that don't need reversing contactors?
- What controllers are available that enable syncing of forward/reverse speeds of two motors to enable simple straight movement of the vehicle?
- Is there anything I could be looking for that uses these motors or controllers to get second hand parts from?

Just realised that with the brakes already set up on the wheels I can still use these for turning by using a micro switch on each lever to disconnect power to the side the brake is applied. I don't really need zero turn so that may help keep the cost down. I was originally thinking the wheel brakes would end up just being a parking brake and the controllers used for full turn control. I think I need to find information on other EV vehicles that use skid steer control systems.

Open to any ideas or links to information on how to do electric skid steer with a separate motor driving each side (assuming this will be the best way to control it).

Video walk round of the 6x6 can be seen here http://youtu.be/VfX-g4PV5s0

Thanks. Steve.


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## major (Apr 4, 2008)

YourSolutions said:


> - What type of DC motors and controllers can I use that don't need reversing contactors?
> - What controllers are available that enable syncing of forward/reverse speeds of two motors to enable simple straight movement of the vehicle?
> - Is there anything I could be looking for that uses these motors or controllers to get second hand parts from?


Separately Excited (SepEx) (sometimes called Shunt Wound) DC motors offer contactorless reversing. These can be found on some golf carts and forklifts. If you use the torque control setting on the controllers and have a control throttle for each, going straight should be easy for the driver. Auto-synching isn't necessary and would be complex IMO.


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## YourSolutions (Jul 21, 2014)

major said:


> Separately Excited (SepEx) (sometimes called Shunt Wound) DC motors offer contactorless reversing. These can be found on some golf carts and forklifts. If you use the torque control setting on the controllers and have a control throttle for each, going straight should be easy for the driver. Auto-synching isn't necessary and would be complex IMO.


Thanks major, I'll start looking round for a couple of old golf carts. I get the feeling they will be easier to find than forklifts here. I called one of the big golf cart resellers here and he said there was no market for used parts so all old carts get dumped. Hopefully that is good news for locating a couple of not working units with ok motors and dead batteries. 

I guess the series wound motor out of a golf cart would also work if I get whole carts since they will probably have the reversing contactor. Only reasons I was looking at avoiding a reversing contactor was they are expensive and add complexity if buying individual parts. It was also mentioned in aodshocky's "mini tank/dozer" thread that having reversing contactors would make it jerky to steer.

Thanks again for your reply.


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## major (Apr 4, 2008)

Carts come both ways; series and SepEx. The series motor types typically have a manual selector switch instead of reversing contactors. It's cheaper and the golf carts don't reverse that often so the golfers put up with the big clunky switch. You could use those and just let the inside wheels free-wheel on turns by turning off that motor. There again, series motor control is like torque control, so a throttle for each side should be easy to go straight for the operator. 

But I think you'd really like the SepEx for smoothness.


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## YourSolutions (Jul 21, 2014)

major said:


> Carts come both ways; series and SepEx.
> --snipped--
> But I think you'd really like the SepEx for smoothness.


Thanks again major. I knew the cart motors come in both varieties. At first I thought it won't be much good if I can only find ones with series motors but realised I can still make use of them. Yes would prefer the SepEx if I can find them. Putting together a note to go up on the local golf courses notice boards to see if I can find donors locally. I didn't realise there were so many golf courses in the area.


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