I am modding my XM-3500 to an XM-4500: 4 extra lithium cells, a Goodrum Fechter BMS, a Cycle Analyst with large display, a Kelly motor controller KBL72201 (72 volt, 200 amp, regen), and Kelly 4.5KW hub motor. I've successfully installed the extra 4 batteries and the BMS and hooked up the new motor and controller. I've only spun the wheel off the ground so far.
In the controller's user manual it says to place a precharge resistor over the circuit breaker or contactor (rated 300 ohms @ 10 watts) or damage may result. As far as I'm aware there is no contactor in the XM-3500, just the DC circuit breaker on the battery + line going to the controller.
Is a precharge resistor really needed in a contactor-less system? The circuit breaker doesn't turn on and off like a contactor would, and so theoretically the capacitors should always be charged even while the moped is turned off. The controller shouldn't get surged with sudden current... Unless you trip the breaker and reset it.
Two other observations:
1) The combination of the new controller and motor is much quieter than the original. In the original it sounded like you could hear the actual pulses at low throttle. This seems like better quality. It's probably the controller's configuration that's responsible for the change.
2) While working on the bike and hooking up the new controller I noticed that the 12V system blew it's fuse. I haven't replaced the fuse yet (it's attached to a cable coming off the DC/DC converter by the headlights), but I'm hoping I won't also have to upgrade the DC/DC converter to handle the extra battery voltage. Hopefully the fuse did its job and prevented the converter from blowing out.
Well the manual specifically says to place the precharge resistor over circuit breakers, so I've ordered a wire-wound resistor from mouser . In my original post I was wrong, they actually specify a 1Kohms @ 10 watt resistor, not a 300ohms. By the way, the local Radio Shack only had 100ohms @ 10 watts.
I've also ordered some of the wire connectors that they use in the XM-3500li. I believe the connectors to be Delphi Metri-Pack 150 Sealed Connectors. Here are the Mouser product numbers I got:
2 wire connectors:
Female - 829-12052641
Male - 829-12162000
3 wire connectors:
Female - 829-12110293
Male - 829-12129615
4 wire connectors:
Female - 829-12186568
Male - 829-12186271
The caps in the controller are indeed charged all the time. The only time one needs a precharge is if one is switching the HV on and off to avoid the inrush charging the caps. So a precharge resistor here on these bikes wouldnt help unless you switch off the power via the breaker (or add a contactor) alot. Id rather have the power turn off with the key but thats not the design.
As a follow-up, I installed the 10K precharge resistor over the circuit breaker. The legs of the resistor were long enough to fold into both ends.
I just moved houses and I had to organize all my manuals and things that came with the Kelly Controller parts. In one of the bags was the required 10K resistor! They had included one from the factory. I guess if I had looked at its contents I wouldn't have had to go through this trouble of researching and purchasing this part.