Monday, January 14, 2013

Sunny but windy test ride

The more I thought about my minimum voltage yesterday, the more it was bothering me.  The battery holds a lot more energy than that.  It occurred to me that if the voltage is dropping, but the energy isn't being used, it's probably a loose or high resistance connection somewhere.

The weather was still pretty warm today (and actually sunny and somewhat dry), so I decided to do a decent test run and see if I could figure out what's going on.  First I fashioned a temporary front fender out of cardboard.  Looked kind of ghetto, but it did help a lot.  I rode down Shelburne Rd. and back on the bike path, about half of yesterday's trip.  Throughout the trip, I wasn't completely sure, but I did seem to see 2 different behaviors on the instantaneous volt meter.  At times it would only drop one bar under full throttle (normal), and other times it was down to half.  I also noticed my top speed dropped about 10MPH when this happened.

When I got back, I checked all the connections, and sure enough, I found the culprit.  The connection between the battery and the battery management system (BMS) was still a cheap, standard crimp connector.  It was not too hot to touch, but definitely pretty warm.  When I pulled it apart  I saw a little bit of charring around one of the contacts.  Going to replace this with a Power Pole connector.

Accidentally reset my power stats when I was changing the watt meter over, but enough said/noticed to satisfy me on this.  Round trip was about 8.5 miles.
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