Okay, location NYC.
Kits and batteries from lunabikes.com tend to be what is advertised. Also several people have used ebikeling.com , I did on my first kit install but I think all my problems with that were caused by the *****y e-bay & amazon batteries.
I didn't like the PAS on the ebikeling kit and the $100 LCD display tended to load up with water in the rain. I imagine it rains in NYC too. I'd say omit the display if available. You're not going to get a torque sensor with an add on kit, so your choices are PAS and throttle. And NYC confiscates e-bikes with throttles. I like the throttle that came with my $189 DD drive wheel from e-bay because it shows battery state green yellow red with LED's, and seems to work mostly in the rain. Although the throttle will short out occasionally and have to be dried out. Batteries from e-bay & amazon were both garbage, I got my money back from Amazon since I figured out the voltage was going away in 7 miles before 31 days. Buy a battery from luna or maybe ebikeling.
A little fiddling around to install is usual even if you buy a motor in a wheel. Some dropouts aren't quite wide enough & I had to file down the spacer washers that came with the motor wheel. Some fork slots aren't quite wide enough and I had to grind it out 1/32" with a 4 1/2" body grinder. Use safety glasses with power tools. I made my torque arms out of scrap steel and u-brackets out of strips of sheet metal. Clamps and mounts are 5 mm or 10-32 screws with elastic stop nuts. I had to move the disk brake calipers, the rotors were too far out on the kit to fit my standard mount locations. I made transistion plates 1" long out of aluminum strip and drilled two holes in each, then mounted the brake caliper with stainless 5 mm screws & elastic stop nuts. Such screws & nuts are available in $8 packs from mcmaster.com The SS18 is from a more reliable country than the base stainless fasteners.
Total for my kit was $840 including 1000 W dd wheel with controller, brake cutoff handles & throttle, 17 AH 48 v battery from luna, and $20 battery mount hardware (aluminum strip & 10-32 screws & nuts). You can see the battery on the front of the picture left, wrapped in packing foam to keep it warm in winter & PVC bag to keep the rain off the connection port. An advantage of the home built battery mount - somebody tried to steal the battery last week while I was shopping, removed a half dozen screws, and gave up at that point. Baffled by ****-****. There are two screws and it comes right off but it was not obvious to the non-designer. Integral e-bike batteries, push the button & pull it right out on some models.
I had to buy mating X90 and X70 connectors for the luna battery from e-bay, and they melted when I first tried to install them. Plug the mating connector (not the battery one) in the x90/70 before soldering, use a 130 w iron. I converted the previous batteries from unavailable andersn connectors to Dorman .157" bullet connectors, which will stand 30 amps. e-bay bullett connectors from ***** will melt out under 30 amps. Use a Klein or Ideal crimp tool on crimp connectors and pull test before plugging in.
I didn't use luna's battery voltage display, it looked too sensitive to rain. I have DVM at both my house and my summer camp that I commute to, to charge from 20% to 90%. Chargers both locations, too.
Have fun.
Here's a pic of the setup (complete with regular passenger).
