Thanks for your reply. I read your thread about running a 36V @48V (And I think most of your others about the XD2 here and elsewhere.)d8veh wrote:I started with a 36v version. I added some solder to the shunt to take the current up to 20 amps. That made it pull 33% more up hills. Then I tried the 48v version at 15 amps, which was just about the same as the 36v one at 20 amps, but not long after I got it, I dropped the bike and damaged the motor wire. While I was waiting to repair it, I put the 36v motor in and ran it at 48v. It ran fine, though O could tell that in high gear, it wasn't very efficient, and low gear became too fast to act as a winch. I'd say that there's absolutely no point in over-volting these motors because you lose more than you gain. The 48v one with everything standard has immense climbing power. If you need more speed, you'd be better off with a Bafang BPM, MAC or Q128 with higher current.
I have a 36V battery pack that cost me nothing, 'cept a week of my time and the kind and patient assistance of the guys here. That was intended to power a 36V500 DD kit I bought from Amazon. The thing arrived and dropped straight in and before going through the process of routing the cables, and working out placement for all the controls etc. I decided to take it out for a short spin on pedal power alone. I set off using the middle chain ring and the second smallest cog as normal -- its down hill from my drive for the first few hundred meters and 35m decent -- and everything felt remarkably similar despite the 10.5kg hub motor -- if anything the extra rolling mass made it feel more stable at low speed -- but then I turned around and tried to change into lower gears for the return and discovered that the rear derailleur wouldn't shift down past the middle of 7 rear cogs. The spindle of the lower idle wheel connected with the casing of the motor.
I pushed it home -- which with the steep climb back, and already heavyweight bike and the extra 10+ kilos was bloody hard work. I spent a couple of hours adjust the limits on the derailleur, and tried moving a washer from left side to right side to move the wheel away etc. but whilst I succeeded in getting one more, with the extra weight, the two smallest rings (and granny ring) would be imperative to getting me home if I ever run out of juice. It went back for a full refund.
So now I've been looking around at all the options and I'm whilst I'm pretty much sold on the XD2; I'm still umming and ahhing about 36v or 48v. for 90% of what I do the 36v will be perfect -- more than enough speed on local roads, narrow, bendy country lanes and shared use cycle paths; and enough grunt to assist me with the climb home if I've any power left, and not so much extra weight if I haven't.
But, I occasionally do use a few A roads to get to small towns and villages around the city where I live and on those it would be nice to have the option of a little more than 25kph.
I looked at the prospects of adding an extra 4s4p pack to my setup, but dire warnings of ensuring that both packs are balanced, along with having to buy a second charger for that pack and ... has somewhat put me off of the idea. I could perhaps sell the 10s4p pack I have and buy a 48v pack.
But then I came across wturber's thread about using a DC boost converter. and -- bear in mind I only know as much as I've read, retained, and possibly not fully understood, so don't jump on me if this is garbage; BUT DO TELL ME!
My though is to stick with the 36v pack and add booster. The pack would be wired to the PAS and throttle in the normal way, but I would have a boost button that switches (still thinking about how; I know I need to preload the switch; but what else?) the boost in at (say) 40V. The idea is that most of the time I'd use PAS or throttle depending on my energy levels, but if I want more speed, I throttle up to the top speed using the pack alone before pressing/holding the boost button to increase the speed.
From what you say above, the boost would be useless on hills low-speed hills -- but that could be enhanced by this shunt soldering (or I read, current limiting resistor modification) -- but should be okay on relatively level, long straight runs.
I'm not looking to add to the youtube collecting of hooning vids, just cover the 10/15 miles between towns a little more rapidly.
Wadda ya think?