I was basing it off this:-
i can only say from owning a bbs01b 350w thats its quiet like the video.with programming to 100% keep current & ridden on max assist (18amp to 250s 15amp) i get 20 miles out of a 17.4ah battery. im 14 stone,the speed restrictions off,so 20-22 mph ON FLAT TERRAIN. Also hilly here in west cornwall...always seems like going up something lol. If the TD is that noisy it would drive me nuts ,but ive never tried one.
Battery is an important decision, you can never have enough. I fitted a second batt on my bbs giving me around 35+ miles of high power. My bbshd has a 15ah 52v 20 miles high power and speed. Obviously u get more miles on lower amps.You need to divide the max amps by number of parallels in the batt to get amp drain per parallel. Then buy a batt with cells that can deliver that CONSTANTLY as a MINIMUM. You can look brands of cells up on technical sites for their performance.Stated maximum is for bursts.halve that for constant drain. Many e bike batteries unfortunately state the max as a constant to look good. So be careful and look the cells up. Avoid chinese generic un named cells.Buy a battery with samsung, panasonic/sanyo LG for instance.
As an example panasonic GA cells are rated at 10amps max, thats 5amps const per parallel.If the battery is 5p. then it can deliver 25amps all day. You will have an excellent battery for a bbs01 on full PAS 15 or 18 amps depending on 250w or 350w version. Say you buy cheaper cells 5amp max,so 2.5amp const then your 5p batt can only deliver 12.5amps const.fine if you use full power for short duration ,but not for most of your ride.It will heat up and stress the cells and reduce their life. Getting a 6p 0r 7p battery would enable the cheaper cells to divide the load more,giving 15amps or 17.5 amps all day.
My 52v battery has samsung 30Q cells in a 5p.they are rated 15amp max ,so 7.5 x 5 is 37.5amps const.i sometimes use the bbshd on full 30amp for miles.it barely gets a tiny bit warm even after a 2 mile hill climb.
my 36v batts samsung 29E cells (5amp max,2.5 const) on the bbs01 have a combined 11p so thats 27amps const for an 18amp bike.but when it had the one 6p it was pushing the batt on full power ,which could only deliver 15amps const.
Phew if u managed to stay awake i hope it gives some insight.