BBSO2 & Downtube Mount battery

[Cascadian]

Hello all,
I am a complete noob to the world of ebikes, but I have been reading and researching for a couple months and decided to go ahead and build up my first bike. I already purchased the host bike which is a 2009 Scott Sportster P3 with disc brakes and front suspension. I am looking at buying the Bafang 8Fun BBS02 750W mid-drive motor, but I am wondering about my battery options and the range I can get out of them. I see that many online vendors pair the 750W BBS02 with a Samsung downtube mounted battery pack and usually 29E cells providing around 10.4 or 11.6aH. I have looked on this website and others and can't seem t any personal accounts of using a battery like this and what kind of range it provided.

My goal is to have an ebike that is capable of reaching top speed of 25-30mph and has a range of 10+ miles on mostly flat pavement with using mostly throttle. I am ~200lbs. Maybe some of you more experienced folks around here can let me know if I am crazy to expect that out of this motor and if so, what is more realistic? Also, if there is anyone that has experience with these downtube mounted batteries and can provide a first hand account of their performance and range, that would be great! Lastly, if this setup will not do what I am wanting it to do, can you guys provide any recommendations to a setup that will? I was looking into the LightningRods kit, however I test rode a bike with the GNG motor and did not like how noisy it was.

Thanks in advance!

 

[r3volved]

Teslanv has a good write-up here, though he's using a bigger battery: http://endless-sphere.com/forums/viewtopic.php?f=6&t=56512

Skyungjae also has a good build write-up here using a similar battery to what you're thinking: http://endless-sphere.com/forums/viewtopic.php?f=28&t=64827

 

[astmacca]

750W BBS02 with a Samsung downtube mounted battery pack and usually 29E cells providing around 10.4 or 11.6aH

I have a 48V 500W BBSO2 ( a 750W unit de-rated from 25amps to 18 amps) with the 11aH Samsung 29E celled down tube battery. Bought from EM3ev

2100km on it now.

I pedal quite a lot as i need to exercise, and with a few short hills and often strong headwinds i am getting around 80km range out of it. If i go heavy on the assist and throttle (pretty much not pedalling) i get about 40km.

Running it at 18amps still provides HEAPS of power. I have never managed to get my motor more than warm.

 

[Cascadian]

Thanks for the replies!

Astmacca - that is great info. I know there is lots of variables concerning range, but it sounds like I should have no problem doing my 10 mile roundtrip commute with the 11aH battery, even if I use the throttle most of the time.

I think I will go ahead and proceed with my purchase.

 

[crea2k]

A 10Ah battery gets you about 15 miles with the BBS02 so you should be fine with your 10 mile requirement. It will also propel it to about 25 under throttle and 30 + pedalling too in its stock form. Iv got a couple of ebikes and one has the bbs02 750w kit on it, the fastest iv had it is 30.03mph , but without changing the firmware its restricted to around that speed anyway.

 

[crea2k]

By the way, that was 15 miles just using the throttle mostly and keeping it in top gear most of the time, letting the bike do all the work, obviously you will get further if you pedal and use the gears, but flying along at 25-30 with little pedalling soon eats the battery up.

 

[lcarron]

Btw the 29e can not supply the current needed for 25amps. I recommend to switch to the 25r battery unless you detuned the bbs02 from 750 w to 500w.

 

[MeanGene36542]

I think you'll find that EM3ev is one of the most respected vendors frequented here... particularly when it comes to quality batteries. A link is here: http://em3ev.com/store/index.php?route=product/category&path=35. He also sells the frame mounted batteries you refer to but describes them as "not high performance" per EM3 standards... I would consider other options first... but I've only been ebikeing 9 months...

 

[sculptingman]

I have the 750... With 48v 11 ah battery from Lectric cycle...

Several points should be made... First of all, you probably won't often ride it throttle only... Because you can set pedal assist such that incline is immaterial....everything feels like a gentle downhill ride. I live in mountainous terrain, and my battery, set mostly to a middle PA level, lasts for about 2 hours of riding... If I am averaging 24 mph... Then it can go 24 miles... If I am averaging 18... Then 18 miles.

Secondly... BB drives are superior because they channel power THRU the gear train. If you use your gears correctly, you are LEVELING the load on the motor...which is why they don't overheat on long uphill runs.

Thirdly... How fast it will drive your bike is largely a function of gear ratios.
For example... In your lowest gear the motor won't drive you faster than about 5 mph under throttle alone... But that is using full power if you are going up a 20% grade.

I run an Alfine 8 IGH... My top speed is determined by the primary ratio between chainring and hub. ( and the hub's 8th gear ). So... I run it with an 18 tooth sprocket on the hub...and I get a top throttle speed on flat ground of 27-28 mph.

If I swap out the 18t for the smallest sprocket the hub can take... A 16t... The bike would top out at 31 MPH. So it's your gearing that will determine your top speed... But, just like riding a regular bike... You use your gears to keep the load on the motor manageable... Start from a stop in a lower gear... And work your way up as the bike goes faster... Because in highest gear the motor has the least torque.