Introduction: Kids Polaris Sportsman 90 Quad ATV EV Electric Motor Swap Conversion Using a QS138 70H V3 Gearbox - VOTOL EM-150-2 - DKD Display - Z6 Throttle Kit

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UPDATE: NEW EV conversion version completed using a QS138 70H V3 and a VOTOL EM-150-2SP controller. Oh boy, how fun its is to ride!


I had some questions about my kids quad build figured this would be the best place to post detailed information so others can learn and get ideas on how to build their own. The idea in this build was to convert a quad maintaining the same 23mph top speed as the original 110cc motor in my 2012 Polaris Sportsman 90 quad … yes, they still call it 90 even though it has a 110cc motor.


The QS motor is the second motor installed in this quad, my first one was a 3kw motor found Electric Motor 72V 3000W, Brushless Motor Controller 48V - 72V 50A which worked well with this gear box but was a tad undersized for me to ride. Do not attempt to use this small motor without a gear box ... a no a sprocket combo will not make up for the gearing needed on these quads. If you attempt to gear it with the proper rear sprocket it would be so big that it would be bigger than the rear wheels. You can see me attempt this in my overview video on YouTube, the one where I review all my electric conversion. In that video I have a quick section where my son tries to drive it and it barely moves then the video shows the gear box I installed and than it worked great.


I wanted to try the QS motor and gear box combo so I ordered one and went to work. The motor was an easy install. Since the gear box is built into the motor and came with a 428 sprocket all I needed to do was fabricate motor mounts. Install only took a few hours. Next I mounted the controller and wired it up. This needed more thought as the kit I purchased came with the components; display, throttle, controller and motor but not a completed wiring harness ... nor a how to wiring diagram. This is the kit I purchased QS138 3000W V3 72V 110kmh Mid drive Motor conversion kit with EM150-2SP controller


Beware of chain rubbing!

When I used the include 15T sprocket with the stock chain I notice that the chain rubbed a little because I used a o-ring chain. I ended up going with a 14T to give me more clearance. Refer to the pictures. To avoid this issue you could use a standard chain.

Supplies

1. QS 138 3kW Mid drive motor with 15T 428 sprocket adapter

2. EM150-2SPsine wave motor controller

3. DKD LCD speedometer

4. Z6 throttle with combination switch

5. 72V battery

Step 1: Wiring

The wiring was tricky. Using the EM-150-2 wiring diagram as a place to start, the first step was to connect the ...

1. battery power to the EM-150-2 controller
2. DKD display (J1-16 Lin Signal, which is a one wire communication to the display, and display power directly to 72v battery)
3. a key switch (not included in my kit) to J1-15 which is labeled as E-lock on the diagram
4. connect the three QS motor power wires and motor signal wire (this was a direct plug in, no rewiring needed)

Next we need to connect the throttle which is where it gets a little complicated. The basics needed is the throttle power to J1-5, ground to J1-19 and Line Signal to J1-12. Now we need a way to get it out of Park, what is this you ask? When the controller starts up it is in Park so we need a button or switch to take it out of park and put it in driving mode. On the DKD display this shows as a "P" above the 'gear' notation. When out of park it will show either a 1,2,3,4 or R. I decided to only use the buttons on the throttle right side (I am not using the left side buttons that came with the z6 throttle kit). I decided to use the green momentary button as the park button. The controller defaults this to a switch so it must be changed to a momentary, this changed by checking the "SW" box of "PD1" on the "Port Settings" page (refer to attached screen shot). Here is where you have to get familiar with the software and I am not going to get into this ... you are on your own on this one. Then to get it into revers use the R button. To switch between driver profiles connect the "1 2 3" switch. These are more straight forward to wire.


Watch out for the spark when plugging in the battery!!!

You will find that when you plug in the battery to the controller you will get a huge spark! This is because there are large capacitors in the controller that brings in a rush of current. If you want a disconnect switch then every time you disconnect and reconnect you will get a spark, so what you say. Well if you get between this you will feel it, it won't put you in the hospital but on a the practicality side of things this spark will weld your switch and ruin it over time. To stop the spark you need a 5 Watt 1k ohm resistor that is connected first for at lest 40seconds then you connect the mail power. I used a $19 car audio circuit breaker 300 Amp that I wired in parallel to this pre-charge resistor. This way when I plug in the battery I first trip the circuit breaker, then plug in the battery, wait 1 min followed by setting the circuit breaker. Refer to the picture in this step.

Attachments

Step 2: Batteries

What about the batteries? I used recycled drill 18650 batteries and spot welded them together forming a Li-Ion 18s7p 68 V (75.6 V max) pack that is about 900Wh (~ 12.5 Ah). I used a 60 Amp BMS, alternatively you could find an e-bike 72V battery pack. Which I plan on upgrading to later. For example this battery will provide 40 miles of range and a lot more power than my previous setup.

How big of a pack do you need. This is where you can benefit from my real world numbers. I was able to achieve 81 wh/mi which means if with my 900Wh pack (72v x 12.5ah) I get 900 / 81 = 11.1 miles of range! which is about 45 min of back yard fun.

Remember, you need to limit the current (amps) in the VOTOL controller so it doesn't overload your battery. Again, you are on your own learning the software. Its clunky and the instructions are difficult to understand so be prepared to get frustrated.

Step 3: Finished

This is a very fun machine to ride. I would think this motor would be great for a sport quad build like a Yamaha Blaster, something that had a 20hp or less motor.

This machine will easily do 50+mph and pulls all the way. I used the "1 2 3" switch on the throttle to program three modes:

1. kids mode limited to the stock 23mph
2. kids fun mode limited to 38mph
3. adult only, dangerous unlimited mode ... this is way to fast for this small wheel base, use at your own risk!


Other points:
A. To get the speed to display correctly you will have to enter the circumference of the wheel AND set the pole ratio offset by using this formula using the gear ratio of the gear box and the two sprocket sizes
final gear ratio = 1/2.35 x (15T / 35T ) = 0.17
Pole ratio offset = 5 x 1/0.17 = aprox 29 (this is the number that yo enter into the DKD display)

B. Do the math on the final drive to utilize the full RPM. Be realistic, obviously this machine should not go over 50mph so at 6000 RPM the speed should be 50MPH. Let say you didn't do the math and the gear is set to do 100 MPH at 6000 RPM then the motor and controller will get hot because it is working too hard. This would be wasting torque by not utilizing all the RPM. This site has calculators to help you figure this out https://www.blocklayer.com/chain-sprocket.aspx Zero motorcycle can get away with not using gear reduction because they use very large sprockets on the wheel and they don't use all the RPM of the motor. Zero can also get away with this because they are using very powerful motors for the weight of the vehicle. That being said I will be building an adult quad next and I will be using a direct drive (no intermediate gear reduction). I can get away doing so because by design have a ridiculously powerful ME1507 that I want to use in a very light weight sport quad that usually only has 30hp.

C. Did you notice that the motor is running clockwise? The controller and motor comes stock running counter-clockwise so I had to switch the direction because my chain is on the left side. To switch the direction of the motor with the EM family controllers you swap the Hall sensor wires Yell-Blue and swap the motor phase wires Blue-Green.

Enjoy and Cheers!
Patrick Basten
bastens.com