Try to build my first ebike

[patpatbut]

Hi Pat Try the links below looks just what you need

Bafang 48V**BPM**500W Rear** Ebike kit - Elifebike Online Store


48V 10AH LiFePO4 Alloy Shell Battery Pack For EBike - Elifebike Online Store

I will add I recommend Rear Motor because with this power the rear off the bike is much stronger also in the wet the front motor can spin out off control this is a serious bit off kit for climbing hills




Frank

Thanks. You make me to think about getting a rear motor instead. I need a better traction

Had a quick check both BMSbattery and GBK sites and they do not offer Bafang 36v 250w rear motor.

Anyone know how to source it?

Thanks.
Pat

 

[Deleted member 4366]

How about this battery

48V 10Ah Li-Ion Alloy 03-CASE EBike Battery With a Carrier Rack - BMSBATTERY

Would the supplied 36v 250w still be able to work for this voltage?
I believe BMP K5 motor is tougher than Q100 so it should able to gain steady 20mph right?

Any idea?
PAT

the BPM motor is very poweful and can maintain well over 20 mph, but you have to get the higher speed version and a battery capable of feeding it 25 amps. The BPM motor is also relatively heavy. I agree with Frank that a rear one is better unless you really know what you're doing.

20mph can be sustained for a short while with the QSXK5. but you need 44 or 48v and 17 amps at 44v and 15 amps at 48v - and no more, so I would stick with the 36v 6FET controller, which doesn't come in 48v version, but should still be OK. These small motors can give a lot of power, but would overheat if you went everywhere at 20mph and probably wear out quite quickly, while as the BPM is designed for it.

 

[patpatbut]

Thanks guy. To be honest, I still want to build a legal bike 36v 250w.

I wish I could make it running steady 20mph as well for off road purpose.

How about this rear motor

36V QSWXH Rear Drive Brushless Hub Motor - BMSBATTERY

Would it be able to run 20mph with 20amp at 36v?

Will I get a lot of voltage sag using 36v 12ah lifepo4 battery? If not, I would have to 48v with lower amp right?

Pat

 

[Deleted member 4366]

How about this rear motor

36V QSWXH Rear Drive Brushless Hub Motor - BMSBATTERY

Would it be able to run 20mph with 20amp at 36v?

Will I get a lot of voltage sag using 36v 12ah lifepo4 battery? If not, I would have to 48v with lower amp right?

Pat

Maybe, but the motor can do it in bursts, but won't last long at a continuous 15 to 20amps, which is what's needed to sustain 20mph.

It depends which 12aH LiFePO4 battery. Yes to the Headway cells one, no to any other.

 

[muckymits]

It depends which 12aH LiFePO4 battery. Yes to the Headway cells one, no to any other.

Second that the difference from my 10.5 AH LiPo to my 12 AH headways is incredible, Ive not managed to make the red light flash on hills yet. It pulls like a train . Once I find a balance lead will be able to see what its really doing.

 

[patpatbut]

Maybe, but the motor can do it in bursts, but won't last long at a continuous 15 to 20amps, which is what's needed to sustain 20mph.

It depends which 12aH LiFePO4 battery. Yes to the Headway cells one, no to any other.

Thanks Dave. This is the battery I am planning to get

36V12Ah LiFePO4 Alloy 03-CASE EBike Battery With a Carrier Rack - BMSBATTERY

Probably you have seen it via my previous post but one thing I am not sure is the following

5. Maximal Continuous Discharge Current: 15Amps.
6. Maximal Discharge Current: 30Amps.

What is the different between them? If I solder the shunt to get 20amp, does this battery still able to give 20amps continuously?

Pat

 

[Deleted member 4366]

5. Maximal Continuous Discharge Current: 15Amps.
6. Maximal Discharge Current: 30Amps.

What is the different between them? If I solder the shunt to get 20amp, does this battery still able to give 20amps continuously?

Pat

You need to read what you wrote. "maximum continuous discharge 15 amps" means exactly that. For a short tiime you can get 30 amps, but noot continuoously. The 12aH Headway cells can give more than 40 amps continuous.

 

[patpatbut]

You need to read what you wrote. "maximum continuous discharge 15 amps" means exactly that. For a short tiime you can get 30 amps, but noot continuoously. The 12aH Headway cells can give more than 40 amps continuous.

Thanks. Sorry I am a bit thick. For "short time" how long is it in real situation?

If I want to gain steady 20mph for 30mins, does it mean I need to ask them to change the BMS to 20A-40A instead of the standard pack 15A-30A to achieve continuous discharge current 20amp?

Pat

 

[Deleted member 4366]

The 15 to 30 amp BMS can give 20A and should be ok for 20 mph on the flat without too much wind.

I'll try and summarise one more time because we seem to be going round in circles a bit.
For sustained 20 mph on more or less flat roads, with a simple cheap kit, you need a Bafang 350 or 500w rear motor kit with 22amp 9 FET controller and a Headway battery of the size to give the range you need. 10ah about 20 miles. 15 ah about 30 miles etc.

You can drive a 250w motor up to 20 amps, but it can't do it all the time, so ok for varied riding speeds. If you go that high on current, you need a battery and controller capable of givimg it. Like the motors, both the basic 15 amp controllers and batteries can also give up to 20 amps, but not sustained.

What length odf time they can be over-powered - nobody really knows. The higher/longer you go, the higher the risk.

 

[patpatbut]

The 15 to 30 amp BMS can give 20A and should be ok for 20 mph on the flat without too much wind.

I'll try and summarise one more time because we seem to be going round in circles a bit.
For sustained 20 mph on more or less flat roads, with a simple cheap kit, you need a Bafang 350 or 500w rear motor kit with 22amp 9 FET controller and a Headway battery of the size to give the range you need. 10ah about 20 miles. 15 ah about 30 miles etc.

You can drive a 250w motor up to 20 amps, but it can't do it all the time, so ok for varied riding speeds. If you go that high on current, you need a battery and controller capable of givimg it. Like the motors, both the basic 15 amp controllers and batteries can also give up to 20 amps, but not sustained.

What length odf time they can be over-powered - nobody really knows. The higher/longer you go, the higher the risk.

Thanks Dave. You make everything quite clear now.

Just wondering one more thing, if I build a bike with 500w motor but restricted to 15mph. Is it still a legal bike?

 

[jerrysimon]

An advantage of the cylindrical 2.3Ah A123 cells is they can manage sustained 69A and peak 138A

Bit over kill for me in that I rarely draw more than 5 or 6A with momentarily peaks of 10-15A lol.

PS My non BMS 12s1p is just coming up to 3 years old, used pretty much daily with 4500 miles on it and about 900 charge cycles to date on it. I have just lost another cell (lost one after the first year through abuse), but easily replaced and the pack is balanced and up and running again

I am currently looking at options to build a slightly larger DIY pack maybe 5-6Ah. I may use some different cells which I think will take the weight of the pack to around 1.8kg. If I wanted a super large pack with loads of grunt I have to admit I think I would consider Headway cells as stated.

Regards

Jerry

 

[Deleted member 4366]

Thanks Dave. You make everything quite clear now.

Just wondering one more thing, if I build a bike with 500w motor but restricted to 15mph. Is it still a legal bike?

The clear answer is "no", another answer could be "only if you have an accident and hurt someone", or "only if you make a nuicance of yourself".

I've never heard of anyone being prosecuted. You can search google. Lots of people ask on every forum, but there's never anybody who says they know of an instance. The more your bike looks normal and you ride it like a normal bike, the less likely they'll bother you.

I you want a legal bike, you have to buy one with a EN15194 sticker on it.

 

[Scimitar]

Just wondering one more thing, if I build a bike with 500w motor but restricted to 15mph. Is it still a legal bike?

Since you're restricting it to 15mph and, I presume, only using the extra power for hills (during which you'll only reach that 15mph anyway) I see no reason to think you'd ever get busted or the bike to be, in any way, a reason for close scrutiny.
It's not a speed demon, by any means, and you won't be attracting attention to yourself.
Put a 250W sticker on the motor and be happy

 

[flecc]

There have been two "over-power" prosecution incidents in England that I know of, though one was dropped on a technicality. In both cases they resulted from accidents, which as d8veh says is the only likelyhood.

In both cases traffic officers were involved and it seems some are more aware of e-bike law now, possibly as a result of their forces being involved in trialling e-bikes for police duties.

I've also been informed that there was a successful prosecution in Guernsey where the old UK EAPC 200 watt law is followed.
.

 

[Deleted member 4366]

There have been two "over-power" prosecution incidents in England that I know of, though one was dropped on a technicality. In both cases they resulted from accidents, which as d8veh says is the only likelyhood.

In both cases traffic officers were involved and it seems some are more aware of e-bike law now, possibly as a result of their forces being involved in trialling e-bikes for police duties.

I've also been informed that there was a successful prosecution in Guernsey where the old UK EAPC 200 watt law is followed.
.

I think you should share the details if you have them.

 

[patpatbut]

Ditto that. Any source or link would be great.

 

[flecc]

I think you should share the details if you have them.

I do know quite a bit more about one of the English cases, but as posted previously, there are good reasons for not sharing at present. I can do so once the new pedelec law has been established when it will become clear why I'm not sharing at present.

Meanwhile it's only fair to inform that some police traffic officers are aware and taking action following accidents. Since both English incidents were fairly recent, it's safe to assume that the risks of prosecution of anyone involved in an overpowered e-bike accident is now much greater than used to be the case when the police had no e-bike usage involvement.

 

[patpatbut]

Thanks Flecc. In that case, I will stick with the 250w kit.

Back to the topic, I could not order the SWXH motor as it is out of stock now. Do you know if BMS battery will have it back in stock?

If I have to get Q100, what is the main different between SWXH and Q100 at 328rpm? It seems Dave recommends Q100 over SWXH at the brompton thread. I thought SWXH is much better choice in term of the reliability and power and I need these factors for running 20mph continuously.

Pat

 

[Deleted member 4366]

328 rpm is high speed (of rotation) for 20" and 16" wheels to make them go about 15 mph. They won't have enough torque for a 26" wheel. If you want legal, then you want the 201 rpm for 15mph in a 26" wheel.
Both motors come with the same controller set to 15 amps, so there's not a lot between them. The Bafang makes a bit of a growl under high load. It feels like a bit more torque but I'm not sure. The Bafang is physically bigger than a Q100 and the heat has an easier route out, so can probably give a bit more power. Saneagle is running his Bafang at 22amps and it seems to be holding out. I wouldn't want to do that with a Q100, but 18 amps should be OK, and I know they burn at 22amps. These comparisons are for the bigger 250w Bafangs. The SWXU is much smaller, so presumably weaker.

To summarise the differences:
Bafang is noisier, rougher, maybe more torque, more tuning potential and slightly heavier
Q100 is smoother, quieter, freer running, cheaper, slightly lighter, maybe slightly less torque and less tuning potential

 

[patpatbut]

What is the main different between 201rpm and 328rpm for SWXH Motor?

If I get 201rpm version and increase the amp to get eqvalent 328 rpm. Would that be the same?

Thanks
Pat