Thursday, July 9, 2009

Super FET working Comments on Sykro Controller

Last week I was mostly on vacation, so I didn't get a chance to really charge the car at full amperage many times. This week was back to work, so I was able to give the charge detector a more reasonable test.

In short, the three huge FETs with heat-sinks seem to work just fine (I should hope so...). I've charged the car seven times in the summer heat and the charger can dump a full 8 amps into the batteries every time without heating up the charge detector box.

I had a little bit of a scare today at work. The Synkromotive controller would instantly fault every time I touched the accelerator. It seems that I had a loose connection between the potbox and the controller. When I wiggled the connector on the TPS (throttle-position-sensor), the controller ceased to go into a fault condition and I drove home. I put anti-corrosion compound on the TPS contacts to help prevent a similar fault in the future. I'll bet that the Sykromotive controller was faulting due to an incorrect input on the potbox wires.

I really like the simplicity of the system. If it fails, it usually fails big and the failure is usually a loose wire somewhere. Get out your Fluke-meter and start debugging.

On my last post, someone left a comment asking about how well the Synkromotive controller was working. In short, it's great. It gives a lot of power when requested and is quite easy to tune various internal parameters through the user-interface over the USB port. Embedded logging makes it really nice as well.

A few nitpicky items I would improve about the controller: The large bus bars that attach to the battery cables are mounted vertically, requiring the use of right-angle lugs or fancy routing of wires. Also, the power given to the motor instantly reflects whatever is specified on the potbox.

If you have a quirky potbox or press the accelerator too quickly, the car seems to lurch a bit. This is especially true if there is slack in the drivetrain from having the motor coast to a complete stop. The lurch instantly takes up the slack in the drivetrain and you can get a jerk that might cause oscillations.

As I've mentioned before, the big solution to this is to use the factory TPS instead of a cheap forklift potbox (like a Curtis PB-5 or PB-6). The factory one is much smoother and more reliable. The downside of the factory potbox is that it never goes to zero ohms which means you can't use it for simpler controllers like a Curtis. The Synkromotive controller has many potbox tuning adjustments so you can set the zero point and the acceleration ramp depending on the travel distance of your throttle cable.

The Synkromotive controller on hot days sometimes gets a temperature noise fault. More recent firmware tends to fix this issue, but I've still stalled once with the latest firmware. Fortunately, you simply need to toggle the ignition switch and wait four seconds for the precharge circuit to run to re-engage the contactor before driving again.

This weekend is the biggest day of the year for our local EV club. We're showing off 30 electric vehicles in Downtown Portland and Mayor Adams is also showing up at our press event to endorse our group. I'm excited but will be happy when it's all over.

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