Bafang at 96V: Would that work?

I'm still maturing my idea about a light and fast ebike.

Now thinking about maybe having a Dahon speed (20'' wheel) with a bafang 48V500W and 2 NiCoMn 48V10AH:
http://www.bmsbattery.com/48v/166-48v-10ah-lithium-ion-electric-bicycle-battery-pack.html

The problem with NiCoMn is its low C rate. For optimal battery life, discharge should be around 1C. So to keep the C low, the voltage has to be higher. I was thinking about putting these 2 batteries in series so I would have a 96V10AH total battery pack at 5.6KG!!! (as light as lipo but safer and with 800 cycles)

With this configuration, I should be able to reach 25-30 mph without drawing more than 10-20 AH with a 20'' wheel. But the question is... Will the Bafang at 48V500W be able to handle that? Voltage is double and I'd probably reach 1500W at 15AH.

It should survive in that size wheel so long as the amp's are low.
And the speed isn't to aggressive for it to pull to much heat. Just have to make sure you get a good controller to boot.

Amps not ah.
Sure, it will handle it for a short burst in terms of heat. But if you run too much watts continuous in any motor, you will be in a situation where at some point in time, depending on the weather that day, you reach a temp where the motor melts.

A true contiuous wattage is one where in the weather that day, you reach a temperatue equilibrium that does not exeed the motors melting point.

I have no idea at what point you have the torque to destroy a clutch, but many gear failures have to do with heat softening the gears. Some motors have now used a higher melting point plastic to fix that. But you might still have the power to snap off teeth if you cross the line by too much.

Personally, I think your approach is silly. Wrong bike wrong motor. Put a Mac or BMC on a bmx or dirt jumper, then run 1500w of 48v into it. Then at least you have a stout frame and a motor likely to take the 1500w continuous a bit longer.

On the other hand, 25 mph is no where near 1500w continous. About 800, which the bafang can do. So really, you aren't talking about fast at all. Merely average fast, but lighter. Still easiest to do with a Mac 8t or 6t on 48v.

hmm.. I tried to put my config on the simulator and I have that:


It seems that at 1C (10 Amps), the bike wouldn't be able to work properly. And according to the simulator, I need at least 20 amps continuous to have a sustainable speed at 96V. So 1500W continuous... Do I miss something here or the simulator is right?


Dogman, the 1500 W continuous is for 30 mph on the simulator. But if I can reach this speed at around 800W and with a lighter motor (such as Bafang) that would be perfect. And also remember our previous discussion about Lipo vs Lifepo4. I listened to your argument and I'm now considering NiCoMn (from BMSBattery) but its optimal C rate is at 1 if I want to have my 800 cycles. So I'm looking for a motor that uses around 10 Amps. (by the way, optimal Lifepo4 C rate is also 1C to have their 1000+ cycles)

20" wheel motor at 48V would be way too slow. I need a voltage high enough to reach 30 mph but with a bike I can still carry on public transport. I know I'm looking for something difficult to reach.

To the OP: is the folding bike and 30mph your objective? I think both are absolutely feasible with the correct would Bafang BPM. I've done that with 26" wheel and 12 wind (201rpm @ 36V) and 74V. With 20" you need the fastest code 8 wind (393 rpm @ 36V) BPM motor, a 48V battery and a KU123 controller. If you want light and don't need much range, consider A123 or lipo.
Cruising at 30mph takes 1000W output power give or take, not 1500W. So you need a battery with 20A continuous and 30A peak.

Miuan, are you sure I can reach 30 mph with a 48V battery? According to the simulator it would be around 24-25mph. I think I need at least 60V or 72V. The other problem is that if I want to use NiCoMn I should pull around 10 amps.

So I don't know what voltage and motor I should use to reach 30mph at 10 amps continuous?

cwah said:

Miuan, are you sure I can reach 30 mph with a 48V battery? According to the simulator it would be around 24-25mph. I think I need at least 60V or 72V. The other problem is that if I want to use NiCoMn I should pull around 10 amps.

So I don't know what voltage and motor I should use to reach 30mph at 10 amps continuous?

Click to expand...

Yes with 48V battery and 20" wheel you will reach about 30mph but you need the fastest wind BPM which is called CODE 8 and has 393 no load RPM at 36V. It's sure a bit faster than I'd ever like to ride a Dahon, but the choice is yours.
Remember to choose 393, not the 201rpm default slow motor.
http://www.bmsbattery.com/rear-driving/350-bafang-350watts500watts-bpm-motor-e-bike-kit.html

As for battery, if you want light and fast, forget low C-rate batteries. You want A123 or lipo.
A123 is great because it has a BMS and you can have a custom battery made of 2.3Ah cells of any parallel count, thus tailoring the battery to your required range, AND still have the power you need.

Ok I see. But why do I have to choose the 36V motor rather than the 48V? wouldn't the 48V be more appropriate?

And why not 60V or 74V like the one you have with your 26" bike? For my intended use, there is no way to draw around 10A?

Ideally, I would like to have a bike that can reach 30 mph only when I need to (long flat road). But most of the time in town I should be around 20-25mph due to the stop and light. If the bike can accelerate quickly to this speed and have a good efficiency around this speed that would be perfect.

ps: A123 seems to be indeed good cells. But it's still a bit expensive. Lipo, lifepo4 and NiCoMn are still of better value

cwah said:

Ok I see. But why do I have to choose the 36V motor rather than the 48V? wouldn't the 48V be more appropriate?

And why not 60V or 74V like the one you have with your 26" bike? For my intended use, there is no way to draw around 10A?

Ideally, I would like to have a bike that can reach 30 mph only when I need to (long flat road). But most of the time in town I should be around 20-25mph due to the stop and light. If the bike can accelerate quickly to this speed and have a good efficiency around this speed that would be perfect.

ps: A123 seems to be indeed good cells. But it's still a bit expensive. Lipo, lifepo4 and NiCoMn are still of better value

Click to expand...

You want a 36V motor because it's made to produce same power / speed that other motors produce at 48V. So if you overvolt it to 48V, you get more speed.

30mph max = 20-25 at stop and light. efficiency will be good at these speeds.

I strongly recommend the A123 packs with BMS if you aren't sure about what exactly is going on inside. You have to pay more, but if you go for 48V pack with high discharge BMS, you will never outgrow that pack.

It's about the winding of the motor, not the voltage. To hit 30 mph you need the winding that has the right rpm at the voltage you choose. Many just pick a motor, any motor. See how fast it runs, then volt up to the desired top speed. A crude but effective approach.

Thanks Miuan. Sorry for my newbiness, but why do they have 36V and 48V motor if they both have the same speed? what's the advantage of 48V over the 36V? (and what does DOD mean? lol)

By the way, I'm still considering other battery option, but I also already have 2 ZIPPY Flightmax 8000mAh 5S1P 30C (http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=16227) at 18.5V8AH. They are 3 months old and about 5-10 cycles. So they are still quite new. I purchased them for a small scooter that's not working yet so I may be able to reuse them.

If I add one more pack, I would then have 18.5V * 3 = 55.5V8AH battery. Would that work with the bike? In that case I may need a controller that can support different voltage, so I can plug or remove the batteries to test the right voltage?

Dogman, if you pick any motor, wouldn't you end up with some that have bad efficiency? And do you have controller that allow you to change voltage? (without changing the batteries)

Depends on the use whether the winding would be a poor choice. Since most motors come with a winding that's middle of the road, most would act about the same. It's actually rare to have much choice, unless ordering straight from china. So when I say pick any motor, I meant any type. Once imported to usa, nearly all are aimed at 20 mph on 36v whether large or small gearmotors, or direct drive motors. So often the question is posed more like this, I have motor x in 26" wheel, what voltage to get speed y.

DOD usually means depth of discharge of a battery.

Thanks for from your explanation Dogman. I understand that any motor is fine as long as it can handle the voltage and amps? So basically, for a specific speed/acceleration, I'll have few set of relevant motors that wouldn't differ much?

But for now, I have a Conhismotor direct drive at 250W (but it uses in average 480W continuous at 36V) with a max speed of 23 mph (average at 14 mph). My average efficiency is at 12 wh/km (full throttle). For similar configuration, I've seen in this forum that other members with a geared motor are only at 8 wh/km. That's much lower than my direct drive. So now I think that at low speed, geared motor are more efficient than direct drive.

You already have a motor that you can relace into a 20 inch wheel but it's too heavy, I really suggest using a lighter geared motor for the Dahon. You also have lipo that can fit your bill very nicely if you buy one more brick and assemble a 15S pack that still works OK with any 48V controller, which is very nice since all you need now is the 36V 393rpm bafang and KU93 or KU123 (for more power) controller. You will need to disconnect the lipo bricks for charging though.
You could also take the 48V 393rpm Bafang and it will be somewhat slower, but will still do 25mph very fast, and top speed will be close to 30mph. It will also be easier on the controller.

Ok thanks, so I think I know what I need.

I'm going to get this Bafang 36V500W kit at 393 rpm:
http://www.bmsbattery.com/ebike-kits/347-bafang-350watts500watts-bpm-motor-e-bike-kit.html

Is the 500W 12Mofset identical to the KU123? I think it's better for me to buy a complete kit so I won't have the hassle to build the wheel (and I've never done that before and I may not have the skill)

And I'm thinking about either adding 1 more lipo (for 55.5V8AH) for a cheap pack, or directly invest in a 48V20AH NiCoMn:
http://www.bmsbattery.com/48v/249-48v-10ah-lithium-ion-electric-bicycle-battery-pack.html

Because it's 20AH, I should be able to pull 20 amps at 1 C isn't it? And that should be enough for my speed. The reason behind this is that I'll probably re-sell my bike in 1 or 2 years. (I'll probably buy a newer/better one) And with lipo I won't be able to sell it again. They are either too dangerous to use (for novice) or the batteries will be dead by then.

If I use NiCoMn, if the calendar life (or shelf life) is not too bad, I may be able to re-sell the complete bike without too much loss. Maybe re-sell it at 2/3 of its value in 1-2 year. Is it a working strategy?

hmm.. I sent a message to BMSbattery about the Bafang 36V500W at 393 rpm with the 48V20AH NiCoMn battery. It seems that it's not going to work..

Jackie said:

Thank you! You can not get 50Km/h. You know high speed means low torque.
The nicomn batteries do not fit the BPM 36V 500W motor. This fits.
http://www.bmsbattery.com/packs/158-36v-20ah-38120-lifepo4-battery-24-cells-ebike-battery-pack.html
And you need to select 30-60A.

Click to expand...

I repeat, if you want light and strong battery, buy A123 or complete the lipo you already have, if you really think you can handle lipo. Go for the 48V 393rpm 20" kit, because the 36V controller will not work correctly. Make sure not to overdischarge the lipo, the Low Voltage Cutoff on Ecity 500W 48V controllers is only 36V.
That headway 38120 battery is very strong but very heavy too, even much heavier than what they state, I guess about 11kg.

Thanks Miuan, I get your point. But could you explain why the 48V20AH NiCoMn with 36V500W motor wouldn't work? Not enough amps? Because I should be able to draw something like 25 amps max.

Also, to make sure I can reach the right speed with my small wheels, isn't it better to have a 36V motor overvolted? I can just change the controller to KU123.

ps: The guy from BMSBattery also told me they are going to have motor that will reach 50 kph within a couple of week and asked me to wait. Not sure what to expect from that.

Hello Cwah,
As you have brought the motor @ 393 @ 36v you could use your current two Lipo bricks (10s1P) at 37v nominal to see how it rides first.
I would also use the 9fet model controller. I don't think your aim is for it to be shit off a shovel quick and at 20amps the power will be fine.

If you really want I know you like tinkering you can shunt mod the power up for torque. Although I doubt you'll need it on a dahon.
If that speed is not what you like. As you are using 5s bricks you could just buy another 5s8000mah battery and have a nice setup that pushes the limits of these controllers (They top out at 63v on the Caps). This would give 687rpm @ 63v lowering to the nominal 55.5v or 600rpm. Which should be plenty quick enough on the Dahon.

I think using the lipo gives you a bit more flexibility but I think with the lower wheel size you won't need the amp's to be very high. An in anycase the Bafang bpm is only rated to 25amp max.

Even with the above setup I would be very suprised if you see anythnig better than 20wh/m - more like 25+wh/miles for that kind of speed which would give you a theoretical range of 15-18miles maybe less depending on throttle usage.

The 96v would mean getting a 96v compatible controller. Which would mean something like a leyn's compatible. At the 600+ rpm it would also be best to use it sensoered rather than sensorless.

I've never really understood BMSbattery's rating on Bafangs. The BPM is actually rated from 350w to 750w on there site and the volts rated at only affect the winding. You can run them on what ever you like but its the winding that counts. Less turns = more rpm per volt but more current needed for torque. The opposite for more turns.

I'd always buy a 36v motor as that would intially give you more rpm per volt than the same speed rated 48v motor.

I'm skeptical as to linking your early metioned batts in series. But ditto on buying the 36V motor, use higher volts for 20". Seems the China sellers don't know their product other than reading their own website.

96volts/30+mph is getting up a little in the danger zone for a basic motor that can perform at 230f but is powered by 200f rated nylon gears. (Wind friction is roughly cubed as speed is squared). The 96V/25A batt/controller may work, though it's possible to peanutbutter the gears if you pull a full 25Amps for 5+minutes. Rolling hills, gentle breezes, <30mph no problem. Lose your throttle discipline in a stiff headwind or long incline, you could lose your gears. 25+mph @ 60V/25A gives you a bit of insurance.

You pay upfront for Ping Batts, but the long term value and their repution is a great investment. http://www.pingbattery.com/servlet/StoreFront

That Bafang is my absolute favorite motor, a close 2nd to any out there, quiet and reasonably priced. I've found the sensorless Bafang with JHR controllers to start up buttery smooth from a standstill. http://holmeshobbies.com/product.php?productid=418&cat=20&page=1 Contact JHR and he may be able to set the amps where you wish. Justin, our ES savior, has a 72V/25A infineon controller as well. See link in my signature after this post.

Thanks for these answers guys.

So Bafang 36V500W at 393 RPM it is. I prefer to get a controller from BMSBattery because I'll buy the kit from them. I'll just ask them to change the controller. So if I take the 9Feet 450W, should I get 36V or 48V? And how would I adapt that to my lipos?

I want to try 37V, 55.5V and 74V to see which one fit the best to my need. According to the simulator, at 74V I should almost reach 50 kph:


Actually, the best config would be like this:
- I'll only use 4 lipos at 18.5V8AH (I already have 2) for a total of 4 kg and 592 WH.
- I'll use these 4 lipos in serie at 74V8AH for short distance. (This is what I do most of the time)
- And use these 4 lipos in parallel at 37V16AH for longer ride. But I may be very very upset with the speed :lol:
- I just need the right cables and change the configuration when required. :lol:

Is there a way to do achieve that with the 9 Feet controller from BMSBattery? (or any controller from them?)


ps: Otherwise I'll directly buy the controller from Justin as I need to get a cycle analyst anyway.
pps: Lifepo4 is really heavy even if it has great value. A123 is also quite heavy because it's basically Lifepo4 cell. So for now I'm only considering lipo and NiCoMn.

Hello again cwah,
You won't be able to go over 63v with the controller you have mentioned. 63v will be the maximum. Unless you get a 72v compatible controller from say lyen.

So forget the above. Fact is you need with the above kit if you increase the volts you need to keep the amps sensible. Unless you really want to push the motor to it's limit and possibly fry it. Or put the clutch and gears under alot of stress.

Depends on your needs. But becareful. Your best setup I think just to try for now will be a controller with a 20amp limit and the speed 393rpm motor and run it on your 10s lipo. See how you get on with it. If your not happy with the speed you can add one more lipo brick 5s and run at the controller max of 63v.
That's 15s lipo and your cheapest option.

If you are still unhappy you can buy another lipo 5s and a 100v compatible cOntroller and have even more speed. But youll already be pushing a small wheeled bicycle.

Lipo you will need some low voltage monitors and probably a watts up meter for a fuel gauge as such. All of which are cheap little add on's for lipo. Then choose some connectors like bullets, ec3 or deans connectors to attach them to the controller and away you got.

You can also buy most of the above in the uk cheaply (well connections and things) from www.giantcod.co.uk
They even do some series or parallel connectors if you can't make your own or don't want to.

Send me a pm if you want and I can call you to help you out.

You dont really need more voltage than the 48V controllers allow. Get a sensored 393RPM motor with a 48V 9 or 12fet controller and one more 5S lipo brick.
Expect 25 to 30 mph top speed. For long range, just throttle back and go slow. No fiddling with batts.
Ultimately, be warned that going over 500/600 rpm is pushing the limits of any geared motor. Don't expect it to last forever.

Ok then I'll listen to your advice.

I get the 393 rpm motor kit at 36V:
http://www.bmsbattery.com/ebike-kits/347-bafang-350watts500watts-bpm-motor-e-bike-kit.html

Then I ask them to change the controller to 48V 9 feet.
I'll buy 1 more 5s lipo at hobbyking for their good price. (I have a little experience with lipo thanks to a second hand scooter I purchased, so it should be ok)

And for the wheel building, I'm not sure about the rim size. According to this site:http://www.bikecalc.com/wheel_size_math it should be 419mm for a 20" wheel (dahon speed.) is it correct?

Is it all ok? (no torque arm required?) And how do I choose sensored motor on the site?

Yes, of course a torque arm is required. Those little geared hubbies in a small wheel, and overpowered through that small axle with tiny flats, put more force on the dropout surface than my big high speed direct drive that wallowed out 1/2" thick steel dropouts.

It's good to see you're off that 96V idea, because that just wasn't going to happen, at least not for long.

John