Too good to be true 7 wh/km with BBSHD ?

ichiban

100 W
Joined
Aug 19, 2018
Messages
197
Location
Bangkok, Thailand
Kind of new here, might not post correctly - sorry for that in advance.
I recently (2-month) converted my entry-level 27.5-in Bianchi 27.1 MTB into an e-bike using BBSHD 48V 1000w kit from AliExpress

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Battery :
Powered by 14s7p 18650 harvested from scrapped laptop batts and DIY into a batt pack. Bulky and heavy (of course! 14s7p = 98cells + caps + stainless bus + nuts + bus bar +..+..+ etc.) but seems with adequate power up to now. I managed to put 500+ km on the bike in about two months. Range per charge is not bad 50km+ with little to moderate pedaling. The BMS is dumb type (about USD20.- from AliExpress again) and I have no clue if it ever balances any cells groups at all, regardless of the bike non-using-period of 3-4 days. The Hi - Lo batt voltage are still 0.2-0.3 V among groups (actually, I spotted about 4-5 groups with low volts compare to the rest) and getting worse with each charge. My charger is Lunar 5-amp 80/100% charge cap and looks like I get less and less capacities when the Lunar charger cut-off. I really never know whether the BMS is still working since no sign if it is alive except that it did not short my cells pack out ... yet.

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Energy used :
Most of my rides are in a big city, flat terrain and normal to congested traffic on public roads.
With 80-90% pedaling, I got 6.xx-7.xx wh/km at average speed of 30+ to 50+km/h, PAS #4-#5 out of 9 levels.
With throttle mostly and little pedaling (less than 5% of the time), I might get 12.xx wh/km.
The power meter I use is the 130-amp GT Power watt-meter (USD10.- or so - a Turnigy clone ?) connecting directly from the batt and before anything else in the system ; controller, motor, display, etc.
Is my 7 wh/km too good to be true ? If yes, should I scrap the 130-a GT Power and change to something else ? What is the recommended watt meter ? I try to avoid that Cycle Analyst since it is waaaay out of my budget. Actually, I'm reconsidering....
But if the above wh/km is realistic, I am just realizing that e-bike is the most practical, most energy-efficient way of transportation there is.

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Future :
Since my current pack sags a lot and I got less and less capacity with each charging. I know the harvested cells are old (some cells might be 10+ yrs old) but this is my first DIY pack and for the sake of getting it done cheaply. Even if I get a smart BMS with all that fancy cut-off/ hi-lo etc. functions, but my pack is about to come to its life span not too long from now ? I learned a bit and agreed with some folks in this ES forum said that DIY pack from old laptop cells are a good way to learn with expensive tuitions ... been there, done that...LOL.
A new pack from EM3EV looks good, that small triangle hard-pack 14S6P with Samsung 35E in it (84-cell of 1000+ wh) - most bang for the bucks, still cost me USD569.- + shipping. Is this a good choice ? I'm not a hard-core rider/jumper just ride for fun and commute when possible.
Might be lengthy but like getting the burden out of my chest asking these questions in the ES forum. Since there is almost nobody around here to ask. The bike mechanics I went to did not even know what I was talking about regarding e-bike. Thanks a lot for any comments and suggestions.

P.S. : I greased the internal gears, all moving parts within the Bafang motor and my front+rear wheels with Mobilgrease 28 during assembling as recommended by many users. When I first opened up the BBSHD, it had very little lubricant in it - almost dry. It is now running smoothly and quiet after 500+km.
 
All are welcome to share their wh/km or any comments. This is by no means to show off, but rather to confirm the effectiveness and true energy-efficient transportation mode a lot of the people still hesitate to join.

Thanks.
 
Go slow enough ( or pedal a lot ) and almost any drive will return crazy good wh/km. A realtime readout can tell you everything. Your power meter might not be lying :)

But you can cross check your realtime wattage with the watts per speed on the ebikes.ca motor simulator just for a quick check.

A Samsung 35E is kind of a weak cell since you have a BBSHD. 6P would be saggy. You'd want 7P or more.. A samsung 30Q on 6P would probably be happy to pump out 30A continuous when needed though.
 
neptronix said:
Go slow enough ( or pedal a lot ) and almost any drive will return crazy good wh/km. A realtime readout can tell you everything. Your power meter might not be lying :)

But you can cross check your realtime wattage with the watts per speed on the ebikes.ca motor simulator just for a quick check.

A Samsung 35E is kind of a weak cell since you have a BBSHD. 6P would be saggy. You'd want 7P or more.. A samsung 30Q on 6P would probably be happy to pump out 30A continuous when needed though.

Thanks for your reply. Agreed with you.

For the 7wh/km I rode fairly fast 30+ to 50+km/hr and pedaled quite hard.
For the 90+% throttle with very little pedaling, I got 12-13wh/km. Sound realistic ?
This info is for me (and anyone - mostly newbies) to determine their travelling range for the remaining batt.

Next to the riding efficiency, my next question will be about DIY batt pack.

Has anyone put a small ventilation fan to suck out heat from their batt pack ? Considering a 2-watt 12/24Vdc power, 3-inch fan connected directly to the 3s/6s group in exchange to a cooler pack (optimistically 5-10 deg C ?). Or that will not help much ? :?:

For most of my moderate rides, the pack rise to only 40+deg C. Since I live in flat area and no hills to climb, I don't have any place nearby to load the bike heavily except to push hard on the throttle. It is hot and humid almost year round, mid-hi 30s deg C most of the time, except for 40+C in the summer and 20s C during a week of winter :?

However, the fun goes on, I plan to go up north for a long haul up mountain ride, a 48-km trip with 2500+m rise in elevation. Only ascending, but down trip might be very dangerous. A bike enthusiast strongly talked me out of the down-hill trip.

That up-hill trip is where I can really test this BBSHD and probably a new pack 14s6p (or two). :D And that might be when the fan is coming into rescue ? Expect 2-3-hour of climb with e-bike (a very long climb with BBSHD + my 2 legs). Normal road bikes take 4-5 hrs. The higher the altitude, the cooler it will get. Seen from youtube that it should be low single digit deg C or even lower during Dec-Jan.

Am I good to make that climb with 2 batts in parallel : a) 14s6p 20Ah & b) 14s5p 16.75Ah, total of 14s 6p+5p and 20Ah+16Ah ?

Will that climb be too hard on the BBSHD, the nylon gear and all the drive train, chain, rear cog, tires, inner tubes etc. (and my butt :( ) ? I have broken one chain after 300+km already. Luckily that it was during cruising at low speed.

Any comments/experience would be appreciated.
 
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