Bms Battery order

[stevebills]

Bms Battery

I have a mtb with 700c wheels and like the kit from Bms and what would be a good setup for front wheel and for 25 mph.
I was looking at there Bafung bpm 350 or 500 watt motor and have read the high speed one is best does that come with the kit or not?
and what the best controller they sell?
I would also like a good battery that will take me 20 miles at least, do i need 48 volts and what amps?
I would like some help picking the parts need so i have a good setup
do they have different rpm motors and how do i choose the right one?
Whats BPM stand for is it a better motor?

thanks Steve

 

[Deleted member 4366]

If you want 25+mph, it might be too much for the front wheel, especially if you have skinny tyres. If you want to use it off-road up hills, the front will certainly spin out. I have a 350w BPM on one of my bikes and I would say that it's OK o the road, but I wouldn't want to put any more power through the front - and it's only good for about 20mph. Our US friends tend to do a lot of what you want because they have a higher legal speed limit, so you should have a look at the Endless Sphere forum, but from what I can see, they tend to use direct drive rear hubs runnig at 48v. For a guaranteed 20 miles, you'll need at least 15ah unless you want to pedal hard, because most direct drive motors don't have freewheels in them , so you wouldn;t want a flat battery I guess, you've thought about getting a 50cc scooter. I think it would be a better solution for travelling at that speed as it should be cheaper- even with tax and MOT.

 

[stevebills]

If you want 25+mph, it might be too much for the front wheel, especially if you have skinny tyres. If you want to use it off-road up hills, the front will certainly spin out. I have a 350w BPM on one of my bikes and I would say that it's OK o the road, but I wouldn't want to put any more power through the front - and it's only good for about 20mph. Our US friends tend to do a lot of what you want because they have a higher legal speed limit, so you should have a look at the Endless Sphere forum, but from what I can see, they tend to use direct drive rear hubs runnig at 48v. For a guaranteed 20 miles, you'll need at least 15ah unless you want to pedal hard, because most direct drive motors don't have freewheels in them , so you wouldn;t want a flat battery I guess, you've thought about getting a 50cc scooter. I think it would be a better solution for travelling at that speed as it should be cheaper- even with tax and MOT.

maybe i could fit a rear hub motor instead at 500 watt and not really interested in a moped as i wanted a push bike with a motor and i realise it can be a bit exspensive and just looking at the optibike for example its cheaper to buy a nice car.

ps. Does Cellman build hub motor kits? and is he the best person to pm?

Thanks Steve

 

[NRG]

If you went for a 285RPM BPM rear mounted motor and ran it in a 26" wheel at 48v by my calcs you would get just under 30mph no load speed...you would need a 20amp controller I would think...

There's a many threads over on ES but here's one that may be worth a read:

Endless-sphere.com • View topic - Bafang BPM Pics and Specs - Large 3.9Kg Sensorless Geared

 

[eddieo]

maybe i could fit a rear hub motor instead at 500 watt and not really interested in a moped as i wanted a push bike with a motor and i realise it can be a bit expensive and just looking at the optibike for example its cheaper to buy a nice car.

ps. Does Cellman build hub motor kits? and is he the best person to pm?

Thanks Steve

I just dont get this obsession with speed....... What you want IS a moped? and NOT an e bike? So needs tax, insurance,testing and a lisence...do you have a licence I wonder

standard 850 watt Optibike illegal on the road as well.......

 

[piotrmacheta]

To get 25mph on the flat is just about achievable but you need a 500w motor running at 48+ volts and 300rpm hub. Range suffers and you will need to be careful not to use too much power from standstill.
You can have the speed but you lose torque for hill climbing ability so it will only work in a relatively flat area and you will need to put in the sffort up the hills.
If you go for a really high powered hub (I know of someone who has a 1.5kw direct drive one) then it's no probs (even spins up the front wheel when going up a hill - 60+ amps) but this is getting silly and the thing weighs a ton.

 

[stevebills]

I just dont get this obsession with speed....... What you want IS a moped? and NOT an e bike? So needs tax, insurance,testing and a lisence...do you have a licence I wonder

standard 850 watt Optibike illegal on the road as well.......

I always drove a 320 bhp subaru st prodrive and that was speed...
and 30 mph on a bike is not a thrill for me and def 15 mph legal speed is a joke as im sure a good rider could do 25+ mph without a motor fitted ............
mopeds dont do it for me so stop going on about them and answer my question please..... as i use my brothers bandit 1200 cc in the summer...

 

[clv101]

I'm still trying to get my head around this area. I'm a reasonably proficient road cyclist (triathlon background) 50 miles at 20mph is a decent morning ride. I'm interested in electric bikes from a technology point of view really.

I'd like to build a bike that provided eclectic assist up to 30mph - certainly not electric only, but say I'm providing enough peddle power to do 25mph, the electric assist would push over 30mph.

For this I need the motor rpm and wheel size combination to still pull at 30mph? So back of the envelope calculation:

26 X 1.5 wheel/tyre = 77.71" circumference.
1 mile = 63 360 inches so 1 mile requires 815 revolutions.
30 miles per hour needs 24460 revolutions per hour or 408 rpm.

What motor still pulls at 400rpm? And what happens at 15mph (~200rpm) or even 7.5mph (~100rpm)?

Are hub motors just not the right tool to cover the 0-30mph range, and I should really be thinking about a motor that interfaces with the bike's chainset and therefore able to use the bike's gears?

 

[Deleted member 4366]

I'm sure it can be done, but it's not as straightforward as it seems. First thing to think about is the weight. By the time you've added all the kit, it'll be a lot more difficult to do 50 miles at 20mph. I've never tried one so I may be wrong but I think you should investigate those free-wheeling crank-drive kits because it'll gives it's power through your gearing to give peak power at a range of speeds.
Electric bicycle DIY kits kit e-bike DIY kits kit Electric bicycle DIY kits kit e-bike DIY kits kit Electric bicycle DIY kits kit e-bike DIY kits kit
I can imagine that if you had a legal one it wouldn't give you much gain at 25mph by the time you factor in the weight and the extra drag on the chain. So then you need more power, which means more weight and you end up with an electric moped like our American friends use with 48v batteries and high powered direct drive hub motors.
If you used a low powered hub motor geared for 30mph, it might give you a little gain on your 25mph pedalling, but it wouldn't be able to pull you from a start and would spend a lot of time at stall speed, which could damage it and would also draw a lot of current.
And Steve, sorry to keep going on about it, but I have to agree with Eddieo. The moment you go over 250w, you have a moped - like it or not - it's just that it's an electric one that in most situations doesn't have any advantage over a petrol one other than it's quieter. You could get away without being noticed on a bike with slightly more than 250w, but when you've got a 48v 20ah battery and a huge pancake thing in the backwheel zipping along at 25 -30mph, you're going to get noticed.

 

[clv101]

If you used a low powered hub motor geared for 30mph, it might give you a little gain on your 25mph pedalling, but it wouldn't be able to pull you from a start and would spend a lot of time at stall speed, which could damage it and would also draw a lot of current.

Thanks, this makes sense. Am I right in thinking these hub motors should only be run at between their top speed and half speed? So if set up for 30mph it would be rubbish below 15mph? The basic systems topping out at 15mph have a useful window of 7-15 which seems sensible?

So for DIY geared hub systems, you have to pick your speed range carefully, maybe 12-24mph would be reasonable, and just remember not to hit the throttle below 12mph to keep the motor efficient and not damage it? Does that make sense?

 

[stevebills]

for those who recomended a moped watch this guy ride

YouTube - Crazy 85 MPH Moped Stunt

 

[NRG]

Thanks, this makes sense. Am I right in thinking these hub motors should only be run at between their top speed and half speed? So if set up for 30mph it would be rubbish below 15mph? The basic systems topping out at 15mph have a useful window of 7-15 which seems sensible?

So for DIY geared hub systems, you have to pick your speed range carefully, maybe 12-24mph would be reasonable, and just remember not to hit the throttle below 12mph to keep the motor efficient and not damage it? Does that make sense?

For hill climbing they are best at half speed but they will still work well at speeds lower than this just not as efficiently. Generally, the geared motors have a nylon gear set so if the rider has configured the bike for a fast top speed they will have upped the power by quite a margin, at low speed where the torque will be very high, this extra power may strip the gears.

Cell_Man over on ES sells the BMC hubs and can fit these with metal gears to get over the problem but it makes the motors quite a bit noisier than they already are.

 

[jbond]

If you went for a 285RPM BPM rear mounted motor and ran it in a 26" wheel at 48v by my calcs you would get just under 30mph no load speed...you would need a 20amp controller I would think...

There's a many threads over on ES but here's one that may be worth a read:

Endless-sphere.com • View topic - Bafang BPM Pics and Specs - Large 3.9Kg Sensorless Geared

Amazing post on that thread about over-volting-amping a BPM motor. Worth repeating here.

I have now started to use my new 48V/15Ah ping battery ... and it's amazing how it works !!

I'm using a 48V/750W controller with a bafang BPM Code9.
Without load max speed is >60Km/h
Max amp peaks is >42A
max power is > 1550W
With nomal pedaling on a flat ground my speed is around 50Km/h
The ability to climb stip road is crazy too !

The battery never go lower than 48V even when when Amps consumed are > 42A !

The battery weigth is definitely higher than a Lipo, but it works very very well, I'm very happy

I had a code11 before, but this code9 associated to the 48V/15Ah/750W is really nice !! I love it !