It’s been an interesting journey for this particular mod. I figured it would only be right to post a brief summary of my process here in case anyone else wants to try this.
Firstly, The Goal: there’s a lot of weird bldc voodoo involved in this that I don’t quite understand but the TL;DR version is that the end result of the mod is a 1.7x lower KV value, 1.7x lower current draw, and as a result of these factors, better startup torque.
The How: Most BLDC motors, including the ones in question, are wired in a “delta” style:
The mod I did was quite simple - change the termination method to a “Wye” style:
To accomplish this, I took apart my motors (I won’t include pictures of this step) and got to work separating the leads of each phase into their start and end leads. This was pretty much just manual based on which strands went where in the stator.
IMPORTANT: Make absolutely sure you don’t have any strands from one phase bundled with those of another phase! Your motor WILL die and you will be sad.
Once the wires were separated, I used this tool to help me figure out which leads corresponded to the start and end of each phase. A good idea is to label each wire coming out of your stator with its phase letter and either “start” or “end.” A multimeter also helps for checking these - A phase should have continuity between its start and end, and there should be no continuity between different phases.
Note on the scheme tool - orientation of the stator matters - for my motor the diagram was accurate from the frame side of the stator, but YMMV.
IMPORTANT: If you mix up the start and end of a phase, there’s a good chance of damaging your motor, ESC, or both. This will also make you sad. Use the tool linked above for reference
Next, I had to remove the enamel from the ends of the magnet wire. This proved to be an arduous, difficult process that I hated very much. The best results came from burning the enamel in question with a hot flame, then sanding each strand to remove the gross burnt residue. Once the copper was nice and shiny, I moved on to the next step.
IMPORTANT: Don’t remove the enamel anywhere except where you plan to solder wires together - you risk shorting your motor phases to each other or the stator. Both of these things would be very bad and would make you sad again.
Here I bundled up the “start” leads of each phase and left the “end” leads dangling for now. My heat shrink didn’t quite fit around all 3 so that’s why the bundle looks a bit funny. You can also see where I semi-successfully tried to tin the ends of the wires. I ended up re-doing that soldering later with much better results.
I then snipped off and twisted together the “end” wires, and soldered them together super solidly. I really wanted a good connection here to make sure everything works properly. The resulting stump got a heat shrink cover, the end of which was sealed by folding over and melting (which smelled awful but worked great).
IMPORTANT: Try your best not to leave any sharp or poky bits when you solder - they can poke through heat shrink and short out your motor which is a very not good thing.
The most important step - sanded off the old KV value and Sharpie’d on the new one.
I slapped these bad boys on some mounts, hooked them up to my Unity, and ran the motor tests. They tested successfully, with resistance 3x higher as expected. I’m still waiting on my controller to arrive, as my old cheap one kicked the bucket a few weeks ago, but I will update on the motors’ performance while riding once it arrives.
I’ll wrap up with a few notes and remarks:
- When separating the phase leads, it helps a lot to untwist the bundles first, and separate them one strand at a time. I used the holes in the stator frame to help me out by threading each strand I was working on through a hole to keep the leads separated.
- When using a multimeter to check continuity between phases, make sure you use continuity mode and not resistance mode like I did. I got all panicky because I saw a slight resistance between two wires that shouldn’t be connected, but I didn’t realize I was touching the wires and the meter was just seeing the resistance across my skin.
- Make really, really sure you’ve removed all the enamel before trying to solder. I ended up having to resolder several wires because the solder just won’t stick to enamel.
- Removing the stator frame would probably make this mod a lot easier. I couldn’t because I didn’t have the tools, but it would’ve helped.
- When wiring up the ESC leads, you can check if you’ve created any unwanted shorts by putting the rotor back on and trying to turn the motor. If it feels like it’s braking, you’ve shorted some phases together.
That’s basically it. Like I said, I’m not sure how these perform in practice yet, but I’ll post an update as soon as I get my board running. If I missed something or you have a question about my process, lemme know! Cheers!
