31 January 2010

Another PEU bites the dust

I was getting close to 18,000 miles. My third Power Electronics Unit has hummed while charging since they installed it. At my last regular service I mentioned the humming but they did not change the PEU.

When Mini engineering visited my home to diagnose the cold weather problem with fast charging, they agreed the humming was not good and directed the dealer to replace my PEU as soon as I could bring it in.

Well, a busy month at work meant I put off going in for service until the regular interval. Friday night when I got home with an ambient temperature of 18 degrees F, I had more than the usual trouble getting the car to start charging at 50 amps because of the cold. After about a dozen attempts to get it to start charging, the humming got extremely loud, the lights in the house dimmed (my wife noticed that upstairs) and the car cut off charging after 5 seconds as usual. I stopped trying to get the car to charge.

I dropped it off at the dealer on the weekend with red tape over the charging port and warned them not to try to charge it until the PEU is repaired. The contacts on the plug and the charging port are dark now, as if it got hot.

Maybe too much attention was paid to over voltage cutoff for safety, since an overly aggressive threshold is what has caused a cold weather problem with the fast charger for a few of us. And the AC Propulsion box has its own over voltage safety cutoff also. Maybe a fast electronic cutoff for over current conditions would be in order. The circuit breaker in the electric panel is enough for human safety but may be too slow to protect the connectors on the car. Over current cutoff might be a good feature for Clipper Creek to add to the wall box.

Hey, I'm glad it happened to me. A civilian might have been upset. I do similar stuff at my job so this does not bother me at all. I actually find it to be gratifying when I find a new problem of this magnitude. I bet Mini and AC Propulsion both learn a lot from this. And I bet nobody else ever has this happen to them. Seems like a one in a million failure mode. Good thing to find and fix before they make a million electric cars.

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