I blew it!!

This past Sunday (happy fathers day) I had decided to run out and make a quick attempt at getting my new controller running. It has been installed for a week or so, but it just doesn't want to run right. On Saturday I had driven it around the block a few times but it felt ... wrong. Getting it moving was a little shaky and my top speed was below what I was getting with the uncapped controller (about 18 to 20 mph tops). To top it off, I had lost connection to my controller and my little Bluetooth program no longer connected. But Sunday I noticed little spots of corossion and so I cleaned up the contacts. Then I was connected again.

After performing a calibration, I decided to take it up and down the driveway. I only had about 15 minutes to blow before family showed up. Then I went to put it in reverse, and it decided that it would not be doing reverse today. The motor would start moving and then stop. So I stuck my foot out the door and *pushed* while flooring it, and I heard a nice *fooof* sort of noise.  Something ... was burned up.

My motor sounded terrible and I was sure that I had completely ruined it. But for the sake of argument I decided to put my old controller back in. Partly because I wanted to see inside of the new controller. But also because I wanted to see if my motor was trashed. To keep things neat, I spent several hours rewiring the old controllers connections. I did it in a way that I could disconnect it easily, and reattach the new one if I wanted to (without having to go through cutting and crimping anything).

Today I drove my car to work, with the original controller installed.  And hey, I made it! So my motor is not trashed (hooray). Although, I do feel like I am missing about 20% of my torque and speed, so a take-apart of the motor is still in order. But now that I had the old controller out, I tore it apart on my desk at work.

And all I can say is YUCK! Once I broke the water tight seal, the smell was obviously that of burnt plastic. If the smell wasn't telling, the exploded black dust sure as hell was.

Here are some pictures, from before I cleaned it up ...

That silver flat bar is actually T-shaped, and serves as a heat sink to those little black rectangular things that are called MOSFETs.

With the heat sink removed ...

Here is a nice show looking down the inner row of MOSFETs.  Each phase cable for the motor has it's own 8 MOSFETs. These just so happen to be attached to the green cable. So does that mean that something shorted out at the green end on my motor? I'm not sure. All I know is that I tried to go backwards, and literally BLEW IT.

Thankfully the damage to the rest of the controller is superficial.  At least four of the MOSFETs are trashed, but I would never replace only the really bad ones. That's going to be an 8-out replacement. At a cost of $3 to $6 each, this will be a costly repair, for sure. There is also a smaller capacitor to the left of the MOSFETs in that bottom picture with a bowed out top. I am not too worry about replacing that one. A capacitor of that size should be about $0.50.

I believe that my next project will be removing my motor to inspect the inner components.  My friend in China who sold me my controller stopped responding to me when I suggested that I may have blown my motor. I hope he knows that I am not blaming his controller for the problems I am having. This is a really, really, cheaply built car. And this replacement controller is actually very well built.

And I neglected to mention that on the DIY Electric Car forum I had a fellow suggest that some of my accelleration problems are likely due to ... a crappy accelerator (the 'gad pedal'). Most accelerators run a range of 1v to 4.5v where they advertise that they go from 0v to 5v. The controller has to then either adjust for the variance, or otherwise tolerate it. This theory made a lot of sense given the jumpy nature of things.

More to come!  Stay tuned!