Unfortunately Alan,
I have two motors, two controllers, both 36v, and both motors are capable of speeds above 20 even speed limiting one of them... Even if I were to limit the amperage on both, to lets say 15 amps, 15 amps would propel the small 20" motor to faster than 20 mph.
The whole reason for having two motors was to allow for my bicycle's amperage usage to be much lower for both batteries, than with a single large battery/motor, hence giving me more range.
While I'm doing 20mph, the current (pun intended) usages are...
The Front battery{15ah}/motor to use only 4.5 amps and the rear battery{30ah}/motor (at the same time) to use only 9 amps.
Hence giving me 3 hours (4.5 amps x 3 =13.5 ah on front batt) and (9 amps x 3 = 27 ahm on the back batt) for a total of 60 miles distance, with some room to spare...
If I cut it down to 3.5 amps on front battery and 7 amps on back battery, that will give me a speed of 18 mph and lets me go for 4 hours for a total of 80 mile range (plus giving me a reserve of 1ah for the front and 2ah for the back which translates into lower DOD and saving a little of recharge cycling.
Since I'm keeping the amps low (hence, using less 'c' rate {i.e. even if I used 5amps for front and 10amps for back, that would still be 1/3rd 'c' rate.)
I charge the front with 3amp Charger ('c'/5) and back with 5amp charger('c'/6)
I have used about 1000 recharges on 'em and they are still 100% soc..
They both read 43.2 when fully charged.
My best mileage has been 111 miles total round trip (while doing approx 17 mph) with wind behind me most of the way, to
BMS cutoff to both batts at the EXACT same time. (first time i've even had them go even CLOSE to
BMS cutoff - Most of the time, I do about 65% of DOD)
Thankfully, I was literally 200' away from my front door.