I finally got to repairing the original controller that failed due to vibration capacitor's shaking loose. Some of you may recall that 1000 miles on rough streets caused one of the phase filter capacitors to come completely detached from the PC board, and the other two had broken leads. Only one capacitor, used as a filter for the 48V power to the MOSFET sink bus, remained connected - it overheated, bulged and melted and shorted the throttle control wires that were touching it. Suprisingly, no MOSFETS failed. So, with the capaciors replaced and the wires repaired, I now have a working spare controller. The only problem was that the 100V capacitors are a bit too tall for the early-style controller case, I had to grind recesses on the case lid. The capacitors are pretty much tight to the lid with the controller closed, but with a dab of automotive sealant on the capacitor tops, they are secured against shaking and are also have a heat sink...
...But, on one of my scooters, I had worse-than expected degradation in acceleration and hill climbing when switched to bigger tires. So, I couldn't resist the urge and added a 1 1/2 inch piece of 12 ga copper wire to the existing three shunt resistors used for controller's current limiter. The shunt resistors are made of an unknown silver colored metal, probably higher resistance than copper but only about 20% the length of the copper wire I added. Nonetheless, I figured with the extra length I would be decreasing the shunt resistance (and increasing current limit) by about 20%.
With the modified controller swapped onto the "slow" scooter, I took it on a test ride. I think I reduced the shunt resistance by more than 20%. The acceleration and steep-hill climbing non- turbo mode is dramatically improved, and in turbo mode is hang-on tight fast! A 12% hill which the scooter (with the 3.50-10 tires) would do no better than 15 mph in turbo now does 20 to 25 mph in _non_-turbo mode. Turbo mode is not needed for normal riding anymore, and I am concerned about burning something out if I use full-throttle turbo to power-up a steep hill or jackrabbit starts.
As expected, this had little effect on level-ground top speed - maybe a mph faster (36-37 mph) - but it sure gets there quicker. So far, with an easy hand on the throttle, I don't think I am experiencing a dramatic decrease in range. I'm sure this would change with a heavy hand on the throttle. I'm concerned about the effect of all that extra current on controller components. Fortunately this is a spare controller, so I can afford to experiment a bit.
I need to fine-tune this shunt resistance ajustment (use aluminum instead of copper wire?) because I certainly overdid it on my first attempt. Any advice would be welcome.