BMS Battery conversion kit

[Hurricane]

I was thinking recently of buying a conversion kit from BMS Battery. I have been looking at the 36v 500w kit by Bafang or they have the same spec by Q128

Rear-Driving - BMSBATTERY

Probably been well covered before but has anyone any experience with these kits. I was hoping to fit it onto a MTB with 26" wheels and disc brakes, suspension etc. Already have batteries at 36v 10ah so hopefully they should be okay.

Would front or rear wheel kit be easiest to fit. I do prefer rear wheel but I think the bike would be more balanced with a front wheel motor and rear carrier battery set up etc.

Any ideas would be really helpful.

Cheers Alan

 

[Deleted member 4366]

Several of us have. Go for the 350w BPM motor. It's very robust, drag-free, quiet and it pulls like a train. You don't need the 500w motor for normal road/trail riding: The 350w one has more than enough power to drag any heavyweight up the steepest hills. I'm not sure but I think the only difference between the 350w and 500w kit is the controller. The 500w controller gives 40 amps, which is a bit fierce for normal riding and you won't be able to pedal fast enough to keep up with it.

Your battery isn't really big enough. 20aH is ideal, although quite big and heavy, 15aH adequate. If you look in my profile, you can see pictures of my bikes with this kit. I also did a review in the reviews section of the forum.

Both front and rear wheel installations have advantages and disadvantages. To fit one in your forks, you have to file out the drop-outs quite a lot to make them deeper and wider. Also, you'll probably need to file the disk carrier a lot to clear the disk. Plus, you'll need to make a couple of torque arms to stop the axle twisting out of the drop-outs.

Rear mounting is a bit easier, but you need to buy a free-wheel gear set to go with it (don't forget to order at the same time if you don't have one already). Most freewheels only go down to 14 teeth on top gear, which means you need a 52T chain-wheel to be able to pedal comfortably at 20mph. Also, you might lose a gear as only a 7 sped one will fit, and even then, you'll have to get/make a couple of washers to space the axle. Finally, front or back, you'll probably have to dish the wheel to get the rim central to your frame, which is not to difficult to do.

All this might sound a lot. It's not just a question of bolting it together. However, it's well worth the effort.

 

[Hurricane]

Thanks for the reply d8veh. Had a look at photo's and they are fab. This is exactly what I am hoping to achieve. I have no worries about filing out the drop outs and fitting torque arms for the front axle.

I assume you would recommend the front wheel installation as I cannot find a rear wheel 350w BPM motor on BMS Battery website.

I also like your review and in particular the cruise control. Will this have kit have this option?

The bike I am hoping to fit the kit to is a Dawes XC 1.8. I suppose most MTB forks are 100mm wide.

Thanks again

Alan

 

[catsnapper]

Just to reinforce D8veh's comments, I run 2 BPM 350W rear units, one on a solo bike, one on a tandem. I use both a 36V 15Ah Ping battery and a 12Ah bottle battery.
Both are about the minimum requirement for reasonable performance, but they manage to haul a tandem with a lightweight (17st) crew up some quite fierce local slopes.
I've also sent you a PM.

Another Alan

 

[Deleted member 4366]

Looks like a good bike for convertion.

I don't have a preference for front or rear drive. I have both and they're about equal, but if it's a heavy battery, I'd say front drive is better handling and safer provided that you make good torque arms. If you want the rear motor, you can order the 500w one and ask them to change the controller to the KU93 controller, or you could order the KU93 as an extra item and then you can try both and see which you like the most, which, as I said before, will probably be the 9FET KU93. Both these controllers have electronic cruise control, which works by holding the throttle constant for about 5 secs and then you can let go and the bike keeps going at that speed. The trouble is, on our bumpy roads, it's nearly impossible to hold the throttle constant except at full throttle, which is no good for battery range. The one on my bike is easily self-made for about £3 and can be fitted on any ebike with a throttle.

Regarding the battery, you have a couple of options. If you think you're going to ride round at 20 mph with a lot of throttle, you need a 20aH. If you want to ride at about 15 to 17 mph and just use the full power to help you up steep hills, a 15 aH would be OK. Your 10aH would work, but its life would be shortened (but impossible to say by how much). Steve (Saneagle) had two 10aH 36v batteries. He took them out of their aluminium cases and wired them in parallel and put them in a bag on his rack, which is very neat and gives all the power he needs. So, you could order another 10aH and do the same, but it wouldn't be best practise. For the difference in price it might be better to order the bigger battery and have done with it.

If you decide to get the kit, we can give more detailed instructions when you install it. It'll take about 4 or 5 weeks to come, or mayb e6 if you order a battery as well.

 

[bode]

The one on my bike is easily self-made for about £3 and can be fitted on any ebike with a throttle.

Could you say how you did it?

 

[Riche]

I bought the 48v 500w kit and battery from BMS.
This is what I have learned.
If you are a heavier bloke expect to be rebuilding the wheel very soon after purchase, My wheel rim split and spokes snapped.
The connectors, main power connectors from the controller to the wheel will fail so get your self 12 x 15 or 30amp Andersons or equivilent (I used 15amp) water proofing of some type will be required. You will also need to buy 2 main switches of some sort one for the handle bars and one on the battery main power (ebay is probably your friend) and make torque thingys and bushes (see frank he has a kit if you need help).

Spiral cable wrap and zip ties will keep things tidy.

Now if I were to buy again.
Buy the motor seperate and lace it into a proper rim of your choice (I bought a down hill rim so I could fit 45c tyres). If you have a rim in mind then you can calculate the spokes you need and can order plenty of them at the same time as the motor and stuff from BMS.
Buy a throttle and controller, Battery and brake cut outs and sensors.

Actually while thinking about it I also had hassle with the rack I purchased, It was the Topeak DX rack (for disc brakes) well it snapped at the bottom so I bought a straight leg one.
I also bought 2 Magura hydraulic cut out switches for my brakes well 1 of these has failed and it been sent back to Germany but as yet still no replacement has been sent back!

http://www.pedelecs.co.uk/forum/electric-bicycles/9344-my-bike.html

Once you have ironed out the small but niggly problems you will have a reliable ebike.

Riche

 

[hech]

I was thinking of upgrading to 48v on an existing machine. Does anyone know if the KU93 controller has a pedelec input as well as the throttle input or is it a question of one or the other? Do the infineon controllers have this capability as well?

 

[catsnapper]

Yes, the KU93 has a separate input connector for a pedelec sensor. My Infineon units don't, other makes may well be different.

Alan

I was thinking of upgrading to 48v on an existing machine. Does anyone know if the KU93 controller has a pedelec input as well as the throttle input or is it a question of one or the other? Do the infineon controllers have this capability as well?

 

[catsnapper]

I
If you are a heavier bloke expect to be rebuilding the wheel very soon after purchase, My wheel rim split and spokes snapped.

Now if I were to buy again.
Buy the motor seperate and lace it into a proper rim of your choice (I bought a down hill rim so I could fit 45c tyres). If you have a rim in mind then you can calculate the spokes you need and can order plenty of them at the same time as the motor and stuff from BMS.
Riche

Hi Riche,

I totally agree with your comments -except why buy more of the same spokes that probably contributed to your initial problems?

I'll admit to a possible bias right now, as I supply custom spokes and rebuild e-wheels, but you've just explained why I have a viable business


Alan

 

[catsnapper]

Hi Riche,

Just looked again at your build thread, really nice conversion of a Scott!


Alan

 

[Deleted member 4366]

Could you say how you did it?

Like this schematic. I bought the switch, little bleack box and 10k linear pot from Maplin. The switch switches between the normal throttle and the potentiometer throttle. Just set the pot to your desired cruise speed and when you switch, that's what you get. As the bike tries to slow down when you go up a hill, the controller automatically feeds in more power in an attempt to maintain speed, so you hardly slow down. With the cruise control set, it's very difficult to tell whether you're going uphill or downhill because your speed is maintained even when you stop pedalling.

 

[Deleted member 4366]

Concerning Richies comments, I would say that the quality of wheel-building is not that good. I had one with loose spokes, and with loose spokes, there's a real chance of damaging your wheel or rim if you hit something. Though not the best, I think that the components are adequate as long as the spokes are tensioned properly, so it would be worth checking them and re-tensioning them as necessary, which you'll probably have to do anyway because you need to re-position the rim to get it central. I've done about 2000 miles on my main one so far. I bump it up and down curbs at least 4 times a day and it seems to take that level of abuse without problems. Personally I'd get the ready-made wheel and adjust it accordingly. If it gives any problems, you can always change rims later. The cost is nearly the same.

One other thing: The Chinese guys are not very good at getting the pins in the correct sequence in the various connectors (throttle, pedelec and hall sensors), so always check that the colours match on each side of the connectors before powering up.

 

[Scottyf]

Must second the wheel building. Imkept the same rim but brought new spokes and I wouldn't say I'm the best at wheel building. But I've not had a problem since.

No punctures, no flex, comfortable ride and everything is slightly dished nicely.
All these little bits do sound like alot but there really very easy to sort with a small fund that youd already have saved from buying direct.

 

[bode]

Like this schematic.

Thank you!

 

[Riche]

Hi Riche,

I totally agree with your comments -except why buy more of the same spokes that probably contributed to your initial problems?

I'll admit to a possible bias right now, as I supply custom spokes and rebuild e-wheels, but you've just explained why I have a viable business


Alan

Hi Alan,
Well after the chinese rim failed I bought 40 DTSwiss Double butt spokes and built wheel with a Halo freedom 29er (700c) rim but they all eventually snapped at the threaded end in the nipples. So I was replacing them with spokes from yourspokes 13G which I think were sapim at £1.00 a shot. Well a friend was putting in an order for stuff from BMS so I thought might as well jumpin and order a bunch of 13g's too from them as they are only $0.20 each so that's about 1/7th of the price?

However I will probably be buying some more spokes soon so if you can provide a link or msg me your details I will be happy to give you a go in the future. Dev's Comments are also true though about the quality of wheel building from china.

Glad you like my build.
Riche

 

[Hurricane]

Well I have taken the plunge and ordered my conversion kits. My good lady decided she wanted another bike as well so following advice from d8veh, scottyf to name but a few I decided not to order the wheels from BMS. I was contacted by catsnapper (Alan at just1bike) and he is going to supply:

2x 36v 350x Bafang motors built into 26" rims
2x KU120 controllers
2x pedelec sensors
2x thumb throttles
1x Brake lever (pair) with cut offs

All this was at an unbelievable price which I am really impressed with. I am sure the spokes and rims will be far better than importing from China.

I now need to think about what else I need. Following advice again I don't think my old batteries will cope so I will probably need 15 or 20ah. Any recommendations?

Will also need torque arms, rear carrier, battery bag, maybe put controller in their too. Would I need some kind of battery fuel gauge?

As my bike has hydraulic disk brakes I will not have brake lever cut offs so will need a On/Off kill switch

Looks like I am going to be busy in the next couple of months. No doubt I will be asking for plenty help.

 

[Scottyf]

Wow ku120 controller and Alan building the wheels. Should be a good setup I think you'll be more than happy.

Just once its all seuo and installed start enjoying it. It will be a fast setup.

 

[Hurricane]

Okay the wheels and controllers and bits have arrived from Alan at Just1bikes. I have to say they look fabulous and very well packaged. Thanks very much Alan

I have been thinking about torque arms. I will be fitting the motor's to the rear of each bike (350w) and wondered if I really need torque arms. I know they are pretty much a necessity on the front but the rear drop outs have a fair bit of meat on them (Alloy) and don't look as though they will need filed out very much.
Comments would be appreciated

 

[Scottyf]

I've not run one. But it is a good fitment and so far it's been fine.
However I've ordered some torque arms from a friend with an engineering firm so hopefully i can add them as a just incase.

If you can get hold of them then it's a peace of mind thing and you know it's safe. My frame is alloy so it wouldn't give memany indication if it was about to go. It just would and by then it would be to late.