Another installment on setting up my build.
This topic is "So your system isnt working and youre trying to figure out if it's the motor or the controller or something else." or "Beginner's notes on popping a MOSFET". There's lots of posts about this on ES, but maybe this will be useful to someone to have all this info in one post.
So for my build wiring seemed to be going fine and I sure AF dont want to talk about how to program a controller - but then I experienced a setback - the motor died. I'm not sure where things went wrong. First, I was testing the motor and controller and was getting sporadic results:
https://www.youtube.com/watch?v=aJTSRYaJqho
The frame rate of the video makes it hard to see but shows a kind of skipping behavior when the throttle was at 0-90%, and then ran at relatively slow rpm at 90-100% throttle around 20s of the video. Then, at one point when tried switching the phase wires and the motor stopped turning entirely. I just hit the throttle and boop, it was dead. This post is of some things I learned to try to fix - the text assumes you know how to run a voltohmmeter and know a few things about electronics. The term "continuity" means if you connect the voltmeter and it measures that you have a complete circuit, the term "short" means there is a connection that you dont want - like, if stand in a bathtub of water and stick your finger in an outlet, that's a short. Avoid.
Throttle testing.
One issue is you throttle may not be compatible with your controller. So I tried two of them, one came with the motor, the other I made using a potentiometer using this circuit:
in both cases I got voltage changing from 0-4vdc on the signal wire of the throttle so that seemed okay. Note: most commercial throttles are based on hall sensors, dont expect that it behaves like a normal potentiometer, you have to have power going to the throttle to see voltage changes on the signal wire.
Hall sensors
Hall sensors inside the motor are set up to detect rotation of the magnets on the stator as they rotate past the stationary stator. My controller has a five wire connector - the red and black wires are for ground and +5v the three other wires correspond to each hall sensor. When the hall connector is powered, if you put the voltmeter on gnd and each one of the hall wires, you should see it vary from 0-4vdc or so when you spin the motor. In my case they were all working fine.
My connector:
https://i.imgur.com/wwUwhVc.jpg?1
View of halls inside the motor:
https://i.imgur.com/vAB2GIb.jpg
Motor tests
A QS205 is a simple animal. Check the hall sensors, they're okay. Other things to test:
- to find a short, put connect the continuity tester on each of the phase wires one at a time, and an outside chassis of the motor, you should not get a short
- connect the continuity tester between the plus wire and an outside chassis of the motor, you should not get a short
- connect the continuity tester between the negative wire and an outside chassis of the motor, you should not get a short
- connect the continuity tester from one phase wire and another the phase wrie, you should get continuity, or very low resistance
Finally, you want to know your motor will generate some electricity. Motors are basically generators. Turn the motor you should get some electrons out. You can test this by putting your voltmeter on each phase wire, or I have a light tree from back in the day when i used to discharge smaller lipo batteries. So, connect up lights on two phase wires, turn the motor, see if this thing can generate current:
and away it goes.
Then there's the slam dunk. Another way to rule out the motor - if you got it, why not try another controller? In my case I was also lucky because when i ordered the motor it came with a 70amp controller. At first I didnt bother with it, but since the motor may have been toasted i went through the programming steps, and eventually got the motor working. The motor turned. Fine, so ruled out motor problems.
Controller aint working? Check your MOSFETs.
Skipping over a lot of detail, MOSFETs are basically valves that when switched on allow monster amounts of current to flow. In the case of my infineon controller, it has an IRFB4110 MOSFET
https://www.infineon.com/dgdl/irfb4110p ... 15a9571e0b
When the controller sends logical signals to the gate, that gate dump all kinds of current. The MOSTFETs get massive current from the plus and minus sides of the input into your controller, and the logic in the controller drives each phase wire of your motor. Well, that's when they are working the way that you want them to. The problem is that these chips have limits, and if they are exceeded what they usually do is short out, and then they dont operate like a valve or switch.
Typically, when they short, it means that you can easily detect problems by finding a short on either the gate dumping something to the plus or minus side of your controllers input, and in my case i also had a short going to the phase wire as well.
One quick way to test your controller is to leave it connected to the motor and to turn the motor by hand. The motor should turn as smoothly as it does when it is not connected. In my case it didnt turn smoothly.
Another simple test can be done with your voltmeter and is described here:
https://www.ebikes.ca/documents/BlownMosfets.pdf
This involves checking the resistance between the negative line going into your controller, and each of the phase wires. Two phase wires should showed around 10k ohms, one of the phase wires was around 0.18ohm. Next check the resistance beween the positive line and each phase. In my case two of the phase wires were 10k, and the same bad line read 0ohms. A short between one of your phase wires and either of the negative or positive line is bad news.
Another step you can take if youre interested in trying to repair your controller is open it up and get access to the MOSFETs.
I picked this up from this link:
https://www.youtube.com/watch?v=lTssCn5YyTw
When I went into my controller there's a large cooling block to serve as a heat sink for the fets, and the easiest way to test them was from the bottom of the controller. See:
https://i.imgur.com/9aYXCkP.jpg
There is a set of MOSFETs that connect to each phase, and to either the positive or negative side of the controller's pos/neg lines in. In my case three fets serve as gates between each phase, and positive (or negative) line in.
You should be able to find a big fat trace that connects either the positive or negative line in. In my case, I found a short between the positive line in and the fets controlling one of my phases. Boom - those are the fets that I would need to replace.
The controller was beefed up to take more amperage by adding a metric fuckton of additional solder to the traces, and even with a hotair rework station at 500F I'm not really able to melt the solder. A similar sized blob of the solder that I normally use melts no problem - so I'm not sure but one guess is maybe the previous guy used plumbing solder or something. So the bad news in my case is i'm not totally sure I'll be able to swap out the MOSFETs. Anyway, hope this helps someone in a similar situation.
they have to be very precise in length of all all the edges. The clamp em together trick helped a lot with that.
