I ordered a 36V controller from an ebay vendor, tried a few wiring combinations with it and got nothing. Unfortunately hub motor controllers come with little or nothing in way of instructions. And e-bike forums offer little in terms of straightforward wiring help. So I pitched the controller ($25 lost) and decided to just use the existing 24V Hill Topper controller.
Yeah, it was a little risky. But not so much because the controller might burn out. Most hub motor controllers are capable of handling a bit of overvoltage. But because there won't be much undervolt protection. I decided I'd just use the bike's odometer to limit rides to ten miles or so to prolong battery service life.
The mod was pretty straightforward -- I just added a third SLA battery with the same specs (actually it turned out to be the same brand too) in series with the two that came with the Hill Topper kit. I assembled it into a "brick" using double stick mounting tape between the batteries, then wrapping them with reinforced strapping tape. Then I attached and wired the original controller, connector, and switch, then covered the whole thing with black duct tape.
I bought a 36V charger off ebay and wired the connector from the original charger to it. I then bungied the new 36V battery pack to the Loop, charged it up, and headed out for a few test runs.
The new top speed is just shy of 20 mph -- the legal limit for e-bikes. It will run faster than you can pedal the Loop. The biggest improvement, though, is that it has a lot more torque for hills.
I bought some ballistic nylon, buckles, and straps and made a new battery pack bag, using the original Hill Topper bag for a pattern. I didn't take a picture but it looks good.
Anyway, so far it works great.
If you choose to try it, no doubt it's voiding whatever warranty is on the Hill Topper kit. And you could possibly burn out the controller or undervolt the batteries and reduce their useful life. So keep all that in mind and remember it's totally at your own risk.
