Spinning magnets,
Thank you for the vote of confidence. To convey as not to over claim my "expertise" with the bafang BBS-0X units, I have previously spent a month bench only testing a 350w 48v BBS01 (the original) and purchased a 750w BBS02 for the same purpose.
Since I already had bench data, I thought it would be a good idea to implement field testing on the newly received 750w Bafang (unmodified in any way, software or hardware) and collect stock data.
I had another job to perform, that of determining the cause of a problem which one of my vendor clients ran into with a customer - I had just finished testing their 48v 13AH battery (one they ordered for the test so I can tell you it was All Cell) with their kit and determined sporatic cutout was not due to the battery.
Since I had a true 48v pack on hand (I never do) and it was rated 25A continuous, I decided to do some testing using it, that lasted about 45-50 miles and indicated speed range between 20 mph and 26 mph as the battery decay. Even still, I was quite impressed with the unit so I decided to build a 13S lipo which is also rated as 48.1v nominal and mimics the All Cell chemistry voltage ranges which meant it should have been a nice even fight.
The pack I constructed was lesser than the All Cell pack (or they would have you believe) at 13S Lithium Polymer, 2 Parallel Strands (made of 4 x 5S and 2 x 3S) for a total of just 10AH and these were even my older 20/30C packs which already have 100 cycles minimum on them.
Voltage sag under 25A load on the Lithium Ion was close to 1.25v, on the Lithium Polymer sag was .25v at worse going up a 1 mile long hill / trail, pulling 26A the entire time (on purpose) the drop never exceed .5v.
In summary, I don't want to scare you or even tell you that you need to build your own pack but you do need to match your intended (or more aptly your actual) riding style, range requirement, recharge requirement and the one most don't think of battery longevity. Even if you want stability of a prebuilt battery there are options which won't break your bank and you can always build a single, low cost strand of other batteries to test and play with at a fraction of the cost of an entire exotic pack.
Further let me tell you, the 750 does have (all bafang crank drives at this point, imho) its drawbacks, I won't enumerate them here because truth is I am working on an install, calibration, use, tricks and work around methods for the short comings and with all that (I'm pickey as hell) I LOVE my bafang mid drive, no it's not going to compete with my dual stage Astro 3220 powered Hard Rock Pro for downright terrifying accelleration, top speed or power in general but I must say that properly calibrated (derauiler, brakes, chainline, shifter, etc) the stock unit even with it's small issues is the best unit or method of power delivery I have tried yet (and I've tried them all, trust me - except I never tried the Acme Rocket strapped to my back, hmmm)... I wouldn't trade it for anything less than: An identically designed (size, shape, weight, etc - better thermal dissipation and power handling excepted) drive system which used more efficient gears of higher strength and powered internally using a motor of quality akin to an Astro 3205, 3210, 3215 and a 3220....
In my 6 years of reverse engineering, designing hubs from scratch, testing countless vendors equipment for safety, efficiency, power and flaws, building my own prototype systems, supporting all of our inventors here on ES (recumpence, Fetcher, Gary Goodrum, Methods, Kepler and many many more) I have to say, this is the finest method of power delivery yet offered to the general public for kit purposes and it's potential (even with nothing more than proper software calibration) are nearly endless for low to mid powered, easy to build, versatile and efficient eBikes.
Okay there is my .02c for what it's worth, if you post your requirements here or PM them to me I will be happy to assist you in selecting a proper battery for your needs, budget, etc (just don't tell me you have $12.34 because you can't run this off of 9 AA batteries, jk).
Hope this helps!
Regards,
Mike
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