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Old 07-23-14, 04:56 PM   #1
SirKhaal
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Question Bafang BBS02 500W - Which battery to get?

First post here. I've been reading the forum for a while, and I am now ready to start my e-bike conversion...

I decided to go with the Bafang BBS02 500W. I live in Canada, and 500 Watts is the max we can get if we want to stay legal.

I currently narrowed my search to 2 different sets of motor/battery:

1 - Bafang BBS02 48V/500W with 48V/20ah rack mount battery.
2 - Bafang BBS02 36V/500W with 36V11.6AH "bottle" battery pack.

If we exclude the weight / balance issue of the rack mount battery. Is there really a big difference in Power / Max speed / Range between both setup?
And is the 20ah battery too powerfull for the BBS02? Should I get a 15ah instead?

Thanks all!

SK

Last edited by SirKhaal; 07-23-14 at 04:59 PM. Reason: typo
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Old 07-25-14, 11:55 PM   #2
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Hi SK,

I'm pretty new to this as well but this is how I understand it:
Higher voltage = higher top speed. So the 48V kit will allegedly have a higher top speed, unless there is a speed limit built into the controller.
EBike Beginners info - Endless Sphere Wiki

The different AH ratings (20AH vs 11.6AH) are a measure of capacity. More AH = longer distance you can travel on a charge. You can multiply the voltage by the AH to get Watt Hours (Wh) for that battery.
48 * 20 = 960Wh rack mount
36 * 11.6 = 418 Wh bottle battery.

My ebike does about 18Wh per km if I'm going fast without pedalling much, so my range would be:
960Wh / 18 = 53kms on rack mount battery.
418 Wh / 18 = 23kms on bottle battery.

The AH do not relate to "too powerful" or not. So assuming the motor supports 48V (I think it does) then its fine.

Cheers,
Delph
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Old 08-31-16, 08:39 AM   #3
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firstly, 48V 500W is better if you use it for hill.
secondly,generally 48V 11.6Ah battery is enough for it ,you know the full charging of 11.6Ah with the BBS02 motor pedal assist ,it can run 100km around.
anyway, also it depends on the using of the ebike,above is just for your reference.
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Old 08-31-16, 08:59 AM   #4
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Cool, have fun!

Voltage is speed. Current is power (torque). Amp hours is distance.

A 48v motor is going to be 30% stronger and 30% faster than a 36v motor (and need a 30% bigger heavier more expensive battery). With the same amp hours, it will also have a shorter range if you are using its full power.

Nominal wattage is kind of goofy. A 36v*15amps = 540 watts. 48v*15amps=720 watts. So, the 48v battery is going to be more powerful (assuming the current is the same – I doubt they have less current in the 48volt motor – what would the point be of that)?


Post #4 has some generic guideliines to get started.
Small Geared hub motors speeds (RPM & mph)
From there:
36V/500W 19mph (31KM/H) 19 M (31KM) 36V15AH
48V/500W 26mph (43KM/H) 26 M (43KM) 48V15AH
That is a very rough, generic starting point for battery and range.

Motor Simulator - Tools will let you play a lot with current voltage and amp hours (battery) to see the effect of the changes. Not sure what motor you should work with, but in a general sense, the speed/range/distance changes will all be similar.

Just responding to bafangmotor - he is right in that 48 is going to have more power, and more hill climbing ability. 11.6Ah is probably enough – depending on how far you want to go. 20ah is a lot.
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Old 08-31-16, 09:33 AM   #5
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I would go for the bigger battery, always... You will never have too much battery, but sometimes you will have too little battery. JMO
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Old 09-02-16, 09:18 AM   #6
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A big consideration is hills. my 48V, 10 a/h system gets about 20 miles when I ascend a 10 mile 3000' trail (10 miles down doesn't use anything). 175 pounds, no wind.
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Old 09-02-16, 09:31 AM   #7
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I like to keep battery and range calculations simple. For a good real world estimate of range just take the volt of your motor times the Amphour of your battery and divide by 20.

48V * 11.6Ah = 556.8 / 20 = 27.84 miles estimated range

My real world experience has indicated that this calculation can be relied on for most general mixed use riding.

Just my 2-cents thrown in...
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Old 09-05-16, 08:10 PM   #8
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A 52v battery would be an easy option too. All the Bafang controllers can take the mild increase in voltage. You get a very minimal increase in speed but the motor will "feel" livlier near the end of the charge as compared to a 48 which will feel sluggish in comparison
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Old 09-07-16, 10:39 AM   #9
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Originally Posted by 350htrr View Post
I would go for the bigger battery, always... You will never have too much battery, but sometimes you will have too little battery. JMO
I've heard that.

My 1st battery was too big. Just too darn heavy and awkward - and I used the bike much less because of that. Recently I got one much smaller. with 10Ah, I can go 25 miles, and I'm good with that. More battery would make my bike less usable in my case.

I know - I'm odd... ;-)
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Old 09-07-16, 10:41 AM   #10
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Quote:
Originally Posted by NoPhart View Post
I like to keep battery and range calculations simple. For a good real world estimate of range just take the volt of your motor times the Amphour of your battery and divide by 20.

48V * 11.6Ah = 556.8 / 20 = 27.84 miles estimated range

My real world experience has indicated that this calculation can be relied on for most general mixed use riding.

Just my 2-cents thrown in...
That is kind of cool. Did you caculate this on your own, or find it somewhere?

I just use the current of the controller. I have a 14 amp controller that averages 10 amps sustained. with a 10 amp hour battery, I can go for an hour. ;-)
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Old 09-07-16, 12:48 PM   #11
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Quote:
Originally Posted by SirKhaal View Post
....I currently narrowed my search to 2 different sets of motor/battery:

1 - Bafang BBS02 48V/500W with 48V/20ah rack mount battery.
2 - Bafang BBS02 36V/500W with 36V11.6AH "bottle" battery pack.

.... is the 20ah battery too powerfull for the BBS02? Should I get a 15ah instead?
IMO, keep the power system as lightweight as possible. With e-assist, it's very easy to morph a nice riding bike into a barge. You want enough energy for climbing, and 36v should be enough if you gear down and don't try to fly to the summit. To increase a battery packs Ah, it has to get bigger and heavier. If you use the higher levels of power on a Bafang system only for hills and otherwise use the lowest settings with pedal energy, you'll get more than the claimed range from the smaller bottle battery. Often, less can be more.
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Old 09-07-16, 01:05 PM   #12
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Reasons to not get the bigger more powerful battery...

1; A bit bigger.
2; A bit heavier.
3; A bit/lot more expensive.
4; A lot less range and more range anxiety.

Reasons to get the bigger more powerful battery...

1; A lot more usable power.
2; A lot more usable range.
3; A lot more re-charge cycles (could end up cheaper) as you would probably not take it down to below 20% as often,
4; A lot less range anxiety, worth a lot if you really need the assist to get back home...

EDIT; As for never having a battery that's too big, I meant too much power...

Last edited by 350htrr; 09-07-16 at 01:27 PM. Reason: add stuff
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Old 09-07-16, 02:05 PM   #13
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I like to pedal, so I'm sticking with low voltage (36v) and low current (10-15a), so that the motor power matches my leg power. But more power can be fun - just reduces the incentive to pedal as much.
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Old 09-12-16, 09:59 AM   #14
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Originally Posted by chas58 View Post
That is kind of cool. Did you caculate this on your own, or find it somewhere?

I just use the current of the controller. I have a 14 amp controller that averages 10 amps sustained. with a 10 amp hour battery, I can go for an hour. ;-)
I found that early on in my research regarding reallistic range. Unfortunately I don't remember where, but it was one of the very experienced electric bike guys that writes on the web.

Electric motor efficiency really hasn't changed in many, many years. It's battery power to weigh ratios that are getting better and better. I hope that mild mannered genius Elon Musk can break new barriers in that respect with his Sparks Neveda battery plant.
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