Cheap Brompton Conversion Kit?

I have been following the thread where d8veh is helping a member spec a new build.

He has found a new supplier Greenbikekit.

I had a look around the site and they are offering what looks to be an end of line 24v kit for a 16" wheel including a 24v,10aH frog battery, which maybe could fit a Brompton. It is important to select the 328rpm version the other options are personal preference.

It works out at $362.67 ( approx £230 ) including the cheapest Fedex shipping.

You would also incur maybe £65 import/courier fees, so total cost around £295.

You would need to get the front fork stretched to 100mm.

Not leading edge tech, but a cheap first conversion.

I offer no guarantees that this would fit, no doubt it will need some tweaking.

edit:

They also accept Paypal as a means of payment.

You will need to check with them that the motor is for use with v-brakes and whether it is sensorless or hall.

http://www.greenbikekit.com/index.php/24v-250w-gbk100f-electric-bicycle-kit-with-frog-battery.html

Edited August 24, 201213 yr by shemozzle999

The kit is almost good, except that the rim for 16" is probably not the right size.

Check with them if they provide a 349mm rim size or if there is any way they can lace such a rim for you.

Most probably you'll have to find a rim in UK and ask a professional to lace it for you (catsnapper do it for a very good price with good quality)

Hi guyz, I was the one having the first build post.

Sorry for hijacking your post. I do have a brompton hanging around as well and I want to do the conversion for my second project.

what is the different between bafang SWXK5 and GBK-100F motor?

What is sensorless or hall motor?

thanks guys

Pat

SWXK5 can handle a bit more power. GBK-100F (believe the same as Cute Q100) is quieter and smoother and a bit lighter.

Using hall sensors in the motor improves the controller timing, so you get a smoother start and a slight efficiency gain. The downside is that the solder joints on the halls can fail due to vibration or they get shorted when water gets in. It seems that problems with them are not so frequently reported as they were a few years ago, so I guess production processes and quality controls have improved. Personally, I have sensors in all my motors and I've never had a problem. The controllers that BMSBattery and Greenbikekit sell can switch between sensor and sensorless modes, so it makes sense to get a sensor motor if you have a choice, and if a hall fails in the future, you just pull the connector off and the controller will switch to sensorless mode.

Timing in sensorless controllers has also improved as the electronics gets developed further, so there's not as much difference as before.

Hi patpatbut,

The Bafang SWXK5 motor they sell is rated 201rpm, suitable for 26" diameter wheels, you would need the 285rpm version for a Brompton.

Brushless motors can be either sensorless with only 3 phase wires to drive the motor or Hall sensored which have an extra 5 wires to which sense the rotation and speed of the motor.

Hall sensored motors are smoother in operation but could be less reliable because of all the extra wiring.

cwah - good point - awaiting clarification email from supplier.

Edited August 25, 201213 yr by shemozzle999

thanks guys.

In that case, which kits is better for the brompton conversion? 24v or 36v one from greenbikekit?

Regards

Pat

Edited August 25, 201213 yr by patpatbut

Pat I am a big fan of Tongxin motors for Bromptons if you want to keep it light. If you want raw power then a Bafang is probably better.

24v will draw more current and require more substantial wiring.

Whilst I agree this is a great deal, fitting a 100mm wide motors into Brompton 75mm wide front forks requires quite a big stretch. Also these more powerful motors will probably require a torque arm.

You may be interested in my Brompton build threads

Super light Goldant motor conversion

Tongxin Nano conversion

Regards

Jerry

Edited August 25, 201213 yr by jerrysimon

Ps

You may be interested in my Brompton build threads

Super light Goldant motor conversion

Tongxin Nano conversion

Regards

Jerry

Not good news - I just had an email reply from Ms Alice at Greenbikekit - looks like a no-go situation.

Dear Shemozzle,

1. Just checked for you, for the motor you need, we are now out of stock.

2. Our rim is different.

3. The max capacity for our frog type battery is 10AH.

Pat I am a big fan of Tongxin motors for Bromptons if you want to keep it light. If you want raw power then a Bafang is probably better.

 

24v will draw more current and require more substantial wiring.

 

Whilst I agree this is a great deal, fitting a 100mm wide motors into Brompton 75mm wide front forks requires quite a big stretch. Also these more powerful motors will probably require a torque arm.

 

You may be interested in my Brompton build threads

 

Super light Goldant motor conversion

 

Tongxin Nano conversion

 

Regards

 

Jerry

Hi Jerry,

Thanks for your advice! Can you tell me how to source those components?

Is any company supplying Tongxin motor kit with brompton?

Thanks.

Pat

Not good news - I just had an email reply from Ms Alice at Greenbikekit - looks like a no-go situation.

 

 

Dear Shemozzle,

 

1. Just checked for you, for the motor you need, we are now out of stock.

 

2. Our rim is different.

 

3. The max capacity for our frog type battery is 10AH.

Oh well. What options do I have for the similar setup then?

thanks

All the links for suppliers have been posted before.

Basically you have a choice to buy a ready made kit £700-800 incl battery or source the parts direct from China for a DIY conversion for about 1/3 the cost. Direct from China you will need to be able to specify exactly what you want and have patience whilst they prepare your order and ship it i.e. could take 4-8 weeks. There are obviously different warranty and backup considerations to consider too. For the DIY option the best thing is to buy two of everything, which is still the cheaper option.

Kits try here

Home page

Freedom E-Bikes - Home

DIY try here

http://www.keyde.com/

Motor-OutRider Eshop - EBike Kit Supplier-Complete Electric Bike Conversion System

Regards

Jerry

Edited August 28, 201213 yr by jerrysimon

Thanks jerry

I have checked your DIY job and you are brilliant! I am not electric engineer and I want to DIY

for my purpose I need to travel 20 miles each way. Ideally, it could be run at about 20 mph (at least 15mph)

Would Tongxin motor do this job well? If I use Bafang motor, would I be able to fold the brompton still?

It would be nice if you can advise which Tongxin motor should I get.

Thanks in advance

Pat

For your requirements you would probably be better off with a Bafang or a Cute motor which would need to be over volted if you want to run at 20mph.

The wider 100mm motors do effect the fold as even the narrower 80mm Tongxins do as well. I guess you could still use a Tongxin but again would have to over volt it to achieve 20mph. A Tongxin run at stock voltage will achieve about 14mph unassisted on the flat though I always pedal.

Will your commute be very hilly ?

I would recommend the standard Tongxin Nano narrow 80mm wide motor for your application if you want to go down that route. Note also the Tongxin run very free when not in use, is one of the lightest and certainly the quietest when running.

IMHO for front wheel builds the narrow 80mm wide Tongxins offers the best option for the Brompton. As stated though its not a power house and is really meant to assist you up to 15mph.

Regards

Jerry

Thanks. Jerry

My commute route is not very hilly but it does some hills to climb.

I probably follow your advice to go for the tongxin motor nano. Can you tell me where to buy? Is it 36v with 27xRPM?

By the way, my brompton is m3r and what controller should I get 4 it?

Many thanks

Pat

Pat email sales@h9.com.cn and tell them what you want. The contact I dealt with was cici.

They provide a stock controller that goes with it plus you will need to tell them if you want throttle, pedelec or both.

You need a narrow width (80mm) 36v, 260RPM, for V brakes model. Stock they come drilled with 36h but I think they will drill them 28h for you if you request it. This enables you to then use the stock Brompton rims with all the advantages detailed in my threads.

Regards

Jerry

Thanks. Jerry.

I have emailed to see what she says.

I have looked via the website but they do not mention the name Tongxin motor. Is this the right one?

Hangzhou outrider technology Co.,Ltd.

Btw, can I choose higher RPM (let'sa say 328) to improve the speed? as my commute route is pretty flat and the speed is my main concern.

thanks.

Pat

Don’t forget the Cute Q85 motor is also available in 83mm width. Not as silent as the Tongxin but about the same size and weight and is 328rpm, so slightly faster. I’ve been very pleased with mine in a 20” wheeled Dahon.

You’d need a 36 hole 349 rim for a Brompton as I think the motor is only available in 36 hole.

The KU63 or KU65 controllers work well with it.

Jerry and other that have experience on it, I have been wondering about the difference between the power output between the small geared motors available:

- Tongxin goldan - 1.4kg: 200W continuous max

- Tongxin standard - 2.3kg: 350W continuous max

- Cute 100 - 2.1kg : 350W continuous max

- Bafang SWXU - 1.9kg : 300W continuous max

I've put these max rating number almost randomly, can anyone can confirm or revise these numbers?

I have looked via the website but they do not mention the name Tongxin motor. Is this the right one?

 

Hangzhou outrider technology Co.,Ltd.

 

Btw, can I choose higher RPM (let'sa say 328) to improve the speed? as my commute route is pretty flat and the speed is my main concern.

Yep that looks like the right one though, they have a better waterproof connector now. Just mention to her that you want the one for V brakes (I got a couple of roller brake ones once when I did not specify them correctly which was a challenge) and say its for a small wheeled bike. Cici will send you a PI (order sheet) which should list and have photos of what you are ordering.

As I said you may have to wait 4-8 weeks especially if they need to make one with 28h. 36h ones are fine but you will need to use a Sun CR18 rim which are stronger (does not matter given this lower powered motor) and are more of a challenge to get the smaller 16" tires on and off.

260RPM is the maximum though as I said some over volt them to get a higher top speed.

Regards

Jerry

Edited August 29, 201213 yr by jerrysimon

Don’t forget the Cute Q85 motor is also available in 83mm width. Not as silent as the Tongxin but about the same size and weight and is 328rpm, so slightly faster. I’ve been very pleased with mine in a 20” wheeled Dahon.

 

You’d need a 36 hole 349 rim for a Brompton as I think the motor is only available in 36 hole.

 

The KU63 or KU65 controllers work well with it.

Jerry How about the reliability of both motor Tongxin and Cute?

For me, it seems Cute 85 is a better choice considering the power and weight.

Just wondering why did you not pick Cute 85 over Tongxin for your brompton?

For the battery, is it any good?

36v 20Ah

http://www.ebay.co.uk/itm/36V-20Ah-LiFePO4-Battery-Electronics-Bicycle-DIY-New-Energy-by-SAL-air-mail-/130713417143?pt=US_Rechargeable_Batteries&hash=item1e6f2075b7&_uhb=1#ht_2311wt_1397

Thanks.

Pat

Edited August 29, 201213 yr by patpatbut

How many km do you plan to do Pat?

On a cute85, I would say you would use around 7wh/km if you peddle. With this pack you would have 36V X 20AH = 720WH / 7wh/km = 102 km autonomy?

Do you plan to do more than 100km daily? You can probably get a 10AH and "only" have 50 km distance if you peddle.

This pack is probably overkill for this motor.

How many km do you plan to do Pat?

 

On a cute85, I would say you would use around 7wh/km if you peddle. With this pack you would have 36V X 20AH = 720WH / 7wh/km = 102 km autonomy?

 

Do you plan to do more than 100km daily? You can probably get a 10AH and "only" have 50 km distance if you peddle.

 

This pack is probably overkill for this motor.

Yea it is overkill but how about 15ah? I am tempted to use throttle only for traveling 20 miles each way.

Ok, if you cycle at legal speed (15mph), on throttle only you would use 15wh/miles.

So for 40miles you would need 15wh*40miles = 600wh battery.

Considering you would need about 20% additional power to preserve battery, a 720Wh battery would fit you.

So for your case, a 36V20AH battery would work better for you, if you do 40 miles/day and no peddling at all.

Do you really want to do 40 miles/day?

I'm visiting flat now and I've found one at 13 miles from my workplace. I tried to cycle there with my Bromped (it goes 25 mph) and it's furiously long. 50 mn!!! The place was nice but no way I'm going to do 1h30/day commuting. And my bum hurts after such a long distance.

For you, at legal speed, and you won't be able to go much faster than 15mph because you'll have a small geared motor, it means 90mn minimum each way.

So more than 3 hours / day commuting?

If it's just occasional only, I could understand... but, 20 miles each way, I would almost never do that.

ps: I also have an overkill pack of 1320wh. It means the double of your 36V20AH pack and weight 11kg lol. But I selected this pack because I needed high voltage. Somehow it makes me feel very zen to always have enough power to go home

Edited August 29, 201213 yr by cwah