Right, you are wishing for a hub motor-based off-road bike that retains as much bicycle feel as possible.
But first, let's talk Volts.
When looking at a system, either street or trail, I first look at the low-speed requirements(what hills I will encounter)and pick the motor speed range suitable. Then, I pick the Volts to attain the desired top speed.
In general, for a given top speed, a low-speed motor run on higher Volts will be more efficient than a high-speedmotor run on lower Volts.
If the bike is to be used on bike paths only and do not need to go faster than 18 mph, I would likely(and have)choose 36 Volts.
But a mini motor in general street riding, has a narrow range of speeds, so if I can make that speed range wider without paying too great a cost, I will do so.
The true cost of Volts-
I use mostly LiPoly and occassionly Li-Ion, so the monetary difference is not much. While a fixed amount of $$$ may buy more Ah capacity, the total energy (W/hr.s) is not much different.
But there are costs other than financial-
48 Volts- not much cost going from 36V to 48V. Most controllers work. More cells, BMS becomes a little more complex.
52Volts-many controller will not work.
Above 52V-heavier gauge wire, better connectors, main fuse, pre-charge circuit, even more complex BMS
For mini-motors, much above 52 Volts and the Law of Diminishing Returns start to interject. Small windings start to become saturated. And of course, smaller motor have more restrictive power handling capability. As Volts go up, Amps must come down.
For me, 48 Volts is the ideal because the 48 V controller's LVC of 42V = 3.65 Cell Voltage, perfect.
I way I see it, there are two different ways to approach a hub driven off-road bike.
1)Single larger geared rear mount
2)Two small geared motors in 2WD configuration.
Both have pluses and minuses, the major ones are;
The rider can use the single more powerful rear motor to lift the frt. of the bike to climb ledges, rocks, down trees, etc. Down-sides; Unsprung weight, wheel durability and traction.
2WD- both Dave(D8veh) and I have built 2WD's using the small Q100 201H motors and they work well. The are lite enough (2Kg. each) that they do not effect handling much. Depending on the type of power differenial control, traction can be good to outstanding. Downsides; A single motor with the same Wattage as the combined 2WD will be more powerful (faster) and, as I mentions, not being able to loft frt. of bike.
There is a third option, the 2-speed Xiongda. Interesting, but they have had some issuses and they are very wide. There is currently a thread going about them.
Anyhow, for what's it's worth, that's my take on Volts and hub motors for off-road.
If I was to to build a new "motorcycle type" off-road hubbie, I think I would spend the extra money and go with the Mac over the BPM so I could run something like 52V/40A. With that much power, the CST feature is not really needed because one will only be shifting a few gears, unless, of course, the system goes down
