125cc ATV Conversion

Electric cars, trucks, ATVs, NEVs - things bigger than a motorcycle.
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H2Guy   1 mW

1 mW
Posts: 13
Joined: Dec 08 2020 2:25pm

125cc ATV Conversion

Post by H2Guy » Dec 08 2020 3:18pm

I’ve had mobility issues over the past several years following back surgery and miss going on those long walks with the dogs (and my wife). So I picked up a beater Chinese 125cc ATV brought it back to life and now I cruise along side the pack every night. It’s noisy and am getting lots of questionable looks as we trek through the various paths and fields so I’m starting my electric conversion. All parts are on order and I’ll post pictures and progress over the coming month(s).

2000w BLDC motor and controller (off shore manufacturer)
Dual EGO 56V 7.5Ah batteries (switchable banks: 1 for the drive and 1 for accessories and can be electrically switched)
11:60 sprocket configuration
Power monitor on drive battery

Am not going to cannibalize the existing ATV other than pull the motor and sort out the various mounting challenges of motor, controller and supporting components. I’ll leave the wiring harness in place and connect the accessory power directly to the ATV battery wires (with the ICE out that should just leave the passive accessories : lights, horn).
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H2Guy   1 mW

1 mW
Posts: 13
Joined: Dec 08 2020 2:25pm

Re: 125cc ATV Conversion

Post by H2Guy » Dec 09 2020 9:07pm

Got all the key components assembled and tested ...
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Push button switches for fwd/rev as well as hard/soft start. Have a video and as soon as I figure out how to post that I will. Still waiting on the sprockets so will switch my attention to how to mount it all on the ATV. More to come.

H2Guy   1 mW

1 mW
Posts: 13
Joined: Dec 08 2020 2:25pm

Re: 125cc ATV Conversion

Post by H2Guy » Dec 16 2020 9:19pm

Moving on to the mounting challenges. Motor bracket fab is underway and should fit nicely on the rear swing arm. Some mounting holes once I get the new rear sprocket and have it positioned then paint.
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H2Guy   1 mW

1 mW
Posts: 13
Joined: Dec 08 2020 2:25pm

Re: 125cc ATV Conversion

Post by H2Guy » Dec 16 2020 9:24pm

Have the basic “dash” display fab’d and ready for mounting.
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H2Guy   1 mW

1 mW
Posts: 13
Joined: Dec 08 2020 2:25pm

Re: 125cc ATV Conversion

Post by H2Guy » Dec 21 2020 6:36pm

Still waiting on my sprockets so time to do some hacker fabrication. I need a chain guard and here is my attempt.
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H2Guy   1 mW

1 mW
Posts: 13
Joined: Dec 08 2020 2:25pm

Re: 125cc ATV Conversion

Post by H2Guy » Dec 22 2020 6:17pm

Have two batteries to find a home for in the build and landed on this for the accessory battery. Using a gutted charger for the connection on this one but have a 3D printed adapter for the main power source ...
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H2Guy   1 mW

1 mW
Posts: 13
Joined: Dec 08 2020 2:25pm

Re: 125cc ATV Conversion

Post by H2Guy » Dec 23 2020 8:14pm

All parts are now in so it’s time. I’ve stripped it down and pulled the engine. Will do a thorough cleaning and start to place the components. Still have to find mounting solutions for the main battery, controller and assortment of misc hardware. Once assembled and tested I’ll strip it down again after any adjustments and clean up the frame and plastics.
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H2Guy   1 mW

1 mW
Posts: 13
Joined: Dec 08 2020 2:25pm

Re: 125cc ATV Conversion

Post by H2Guy » Dec 27 2020 6:07pm

Lots of work over the last couple of days and still not happy with the motor/sprocket alignment so will tear it down and get that sorted over the next few days You can see from the pics there’s lots of final assembly to go but did take it for it’s first road test. It’s NOT a beast but knew that going in based on battery selection and motor ratings however it is supposed to be a “touring” machine and it’s going to do that perfectly. No info on range yet but will post all the performance info once it’s closer to being fully road worthy.
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H2Guy   1 mW

1 mW
Posts: 13
Joined: Dec 08 2020 2:25pm

Re: 125cc ATV Conversion

Post by H2Guy » Dec 29 2020 9:47am

First substantial road test this morning. Was too cold (-5c) to stay out cruising too long but went about 7km over 30 minutes and used about 50% of my EGO 56V 7.5ah battery (also have a switchable 5ah on board for reserve). Top speed was 37km/h. Again, the design parameters were to cruise for long walks with the family and dogs so I’m pleased with the performance. Still more final assembly to go to button up all the wiring and aesthetics. Will post more pictures of that progress.

H2Guy   1 mW

1 mW
Posts: 13
Joined: Dec 08 2020 2:25pm

Re: 125cc ATV Conversion

Post by H2Guy » Dec 30 2020 5:12pm

Done till spring when I can strip it down and refurb the plastics and paint. It is fully functional and this will be the last update until I can do some full performance testing. Here are some pics ...
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H2Guy   1 mW

1 mW
Posts: 13
Joined: Dec 08 2020 2:25pm

Re: 125cc ATV Conversion

Post by H2Guy » Feb 14 2021 1:55pm

Done some tweaks over the past few weeks : swapped out the master switch for a 4 position that allows off:Battery A:Battery B: Battery A&B paralleled(along with some diodes to control cross charging if they are at different SOCs), added blue LED under frame running lights and installed an 11 tooth front sprocket. All continues to run fine with good range / run time but still can't get the amps through the batteries for decent low end torque. Think the BMSs in the EGO batteries must limit this. So I've gotten my hands on a few hundred 18650's and am going through them to find and categorize their capacity to build my own pack. Thinking 14SP6 and will post any significant updates as I go but it takes a long time to test each cell so will be a while before I start spot welding and packaging that up.

Have updated the wiring diagram as well.
ATV Wiring Feb 2021.PNG
ATV Wiring Feb 2021.PNG (74.15 KiB) Viewed 364 times

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