Cheap Brompton Conversion Kit?

[shemozzle999]

Yes Jerry,

It is a 28 teeth planetary gear assembly/freewheel unit to fit this motor.
They supply a full kit with the sun gear and ring gear as well, or separate planetary gears only for both 28 and 36 teeth and also a replacement wound stator 24v or 36v.

I am hoping it fits my Bafang SWXK.

 

[patpatbut]

Hi Shemozzle.

How much did you pay them? The shipping costs seems a lot though.

Thanks.
Pat

 

[shemozzle999]

Hi Shemozzle.

How much did you pay them? The shipping costs seems a lot though.

Thanks.
Pat

Hi Pat,

I won't know the final cost until they are delivered; it depends whether or not they attract customs interest.

Regarding the postage fees it is not something you can avoid, they have to be shipped halfway round the globe.

 

[shemozzle999]

shemozzle999
just tried sending a PM (very slow reply, apologies!) and it said your inbox full.
James

Hi James,

I have cleared down some of my messages, it should be OK now.

I now have your old Bafang kit running on my other Brompton; it successfully completed a few laps at Blenheim.
It needed a new wheel rim as the old one was slightly buckled, and the freewheel was sticking occasionally but if you bang the tyre with your hand in the forward rotating direction from a stopped condition it releases it and the hub washers needed slight filing to remove unwanted radii to ensure a tight fit on the forks.
The judges are still out on the frog battery I cannot be certain whether it is failing early because of a cell going down or the controller/bms is kicking in at too high a minimum voltage.
I will run it down on your system and then transfer it over to my other Brompton to see if it will still run.

Time to offer belated thanks to Catsnapper for the spoke order and Cyclezee for the thumb throttle whose usual rapid response made the build possible in time for Blenheim - thanks guys.

One of the reasons for starting this thread was to try and find a set of products for cheap Brompton conversion as we discussed at the hand over of your old kit - I am still working on it.

I have ordered a motor from MW motors, see earlier post, and will let you know how I get on.

Another couple of contenders on the motor front:

250w electric bike kit front drive brushless hub motor QB02-A / Aliexpress.com : Buy 24v 250w mini front hub motor for electric bicycle from Reliable 250w hub motor suppliers on UU Motor Technology Co., Limited

E-BIKE BRUSHLESS MOTOR 250W 36V FRONT MOTEUR AVANT | eBay / Chang zhou hua yu xin feng meachanical&electronic co.,ltd[/QUOTE]

Hi James,

Battery update.


On further investigation of the battery I ran it down on your system then tried it on mine, it also failed, so the low voltage cut out is working OK.

When I recharged it would not reach the charger voltage 29.4v.

I decided to look inside for problems (I would not recommend anyone should do this unless they have knowledge of electronics) the wiring checked out OK but when I metered the individual cells I found the first 2 fully charged but the remaining 5 under voltage.

The cells need to be balanced, luckily there is an inline connector on the balance wires from the battery to the BMS UNIT, so using a battery balance unit I use for RC modeling, I have connected up the first 4 cells and I am currently waiting for it to complete its balancing cycle.

I hope that when this is done I can recharge it to its full capacity.

So the battery is fine, just unbalanced.

 

[jerrysimon]

Having previous experience from messing about in the electric RC hobby environment is a plus for sure

Regards

Jerry

 

[shemozzle999]

Having previous experience from messing about in the electric RC hobby environment is a plus for sure

Regards

Jerry

Yes it helps Jerry but I would always advise returning the battery to the supplier for them to make these checks first.

It would be nice though if all ebike batteries/chargers had both means of charging like we have in the RC modeling game, it would only require an extra connector.

I should have twigged the problem earlier because the charger kept on periodically flashing the red light at the end of the charge cycle.

I think the out of balance voltage (>200mV) was too great for BMS in the battery to cope with.

 

[superDove]

Hi James,


I hope that when this is done I can recharge it to its full capacity.

So the battery is fine, just unbalanced.


View attachment 4201

I'm very happy to hear that, with fingers crossed, you've managed to get it up and running. I know it's been a hassle for you but I'm glad you got the kit rather than someone with less experience.

 

[shemozzle999]

I'm very happy to hear that, with fingers crossed, you've managed to get it up and running. I know it's been a hassle for you but I'm glad you got the kit rather than someone with less experience.

Hi James,

Well it took over 8 hours for the device to balance the rogue cells, I then re-assembled the battery and charged it last night - result 29.3v and after final charger balancing and a constant green light:



There are a couple of useful RC products that can be adapted but the normal maximum sized batteries used are 22.2v i.e. 6 cells.

The balancer shown can support 2 to 6 cell balance and the capacity controller (monitor) can support 1 to 7 cells (OK for 24v ebike batteries)



They are available on eBay:

CellMeter-7 Digital Battery Capacity Checker LiPo LiFe Li-ion NiMH Nicd RC | eBay

New Black RC 2s - 6s LCD Li-Po Li-Fe Battery Voltage Meter Balancer Discharger | eBay


If the ebike industry could have these developed for use with ebike battery configurations they could easily be incorporated into the battery cases, at minor extra cost and give the user more tools to manage the condition of the battery - less return to base.

Just need to go out and do a long run and find out the range - of course I will take my spare just in case I have been typing a load of old BS.

 

[shemozzle999]

Battery update (24v,10Ah)

Hi James,

I finally managed to run the battery down today.

I completed 22.6miles only lightly assisting in headwinds and inclines.

It dropped out at 23.8v (previously dropping out at 26.8v) showing only the red led on the battery indicator.

I have now recharged it back to 29.3v and it took 5 hours on my 2A rated charger.

This equates to approximatley 50% increase in range prior to the cell re-balance.

I hope it stays in balance for a while






p.s.
As the controller and battery BMS are set to cut out at 21v and the battery is constructed using 7 cells in series it equates to 0.4v voltage sag in each cell - I would be interested if this also applies to a 36v system.

 

[Deleted member 4366]

I reckon that there's loads of people that bought new batteries because of low capacity, when all they needed was to balance the cells.

I have one battery that wouldn't give any power, but when I checked the actual cells, all 10 were equal at 4.0v (not fully charged). The charging workd, but not discharge, so I bypassed the BMS for discharge, but still charge and balance through the BMS. The controller looks after LVC.

 

[shemozzle999]

I agree d8veh, same thing applies to aero modeling systems, we can charge our Lipo's through the pos/neg wires or charge, balance and discharge through the balance connector, no BMS in the battery. The ESC (electronic speed controller) protects the low voltage cut off but we need to ensure the motor does not overload or either the ESC or the battery goes up in smoke - hence the reason why the watt meters were made - we can draw up to 130A with our motors.
We have to match propeller size and rpm, much like wheel size and rpm in ebikes

 

[shemozzle999]

Good news / Bad news

The motor from China arrived today via Fedex, unfortunately it has been damaged in transit.

The motor has been dropped and the casing around the spoke holes is cracked.

It must have been dropped when being inspected as there are signs that the parcel had been opened and then resealed.

Jane is in the process of sending a replacement shell, this time via DHL. She has been very helpful and understanding.

So the review will be delayed but I can get on with the fitting and maybe run it up at the weekend.

Now in the process of making a claim with Fedex, wish me luck, I think I am going to need it

 

[shemozzle999]

Managed to fit the motor into the forks today - all good news- plenty of clearance on both sides of the forks using only the spacers provided.

The bonus is the cable exit is on the right side of the bike so no folding problems.

The speed readout under no load was 16.8mph on my bike computer.

 

[jerrysimon]

What are those retaining washers/brackets that seems to cover the front of the dropouts ?

Can we have a side on view please ?

Jerry

 

[shemozzle999]

They were designed and supplied by The Electric Transport Shop TETS in Cambridge. They are CNCed out of aluminium recessed to the shape of the fork ends with a slot milled in to fit tight on the flat of the motor spindle. When installed they stop the fork ends from spreading under load, effectively a torque washer.
Call Matt Widgery he might be able to supply them if you need some.

 

[shemozzle999]

Hi Ben,

I have been emailing MW Motors and it looks like they can supply SWXU motors suitable for a Brompton i.e. 340rpm versions.

I am awaiting their quote regarding prices as it is a public holiday in China at the moment.

Jane, their contact, has become a site member (Jane111008) and is willing to answer simple questions here about their products, but I suspect would prefer communication via their aliexpress comms channel.

I can confirm that this motor is a nightmare to try and get hold of. I tried for ages but gave up and bought the Crystalyte G Series in the end because I couldn't find one.

If anybody finds a source for the 300+rpm bafang then I would buy one now and have a spare front wheel.

Ben




Sent from my GT-I9300 using Tapatalk 2

 

[Deleted member 4366]

I think that the Q100 from BMSBattery or Greenbikekit is a better candidate. It's cheaper, smoother, lighter, quieter and the clutch disengages the hub when free-wheeling for less resistance. It comes in 328 rpm version. If you want more speed, run it with 12S lipos. You can also get the even smaller Q85, which is less of a stretch for the forks.

 

[shemozzle999]

I think that the Q100 from BMSBattery or Greenbikekit is a better candidate. It's cheaper, smoother, lighter, quieter and the clutch disengages the hub when free-wheeling for less resistance. It comes in 328 rpm version. If you want more speed, run it with 12S lipos. You can also get the even smaller Q85, which is less of a stretch for the forks.

Hi d8veh,

The SWXU has the same internal setup so apart from being slightly lighter (less robust?) I can not agree with your assumptions.

I don't intend to overvolt but use it in way it was originally designed for.

 

[Deleted member 4366]

Below are pictures of the motor internals. The SWXU is like a scaled down QSXWK - the same as all bafangs in principle. The Q100 is totally different inside. The motor part is a Tongxin clone, but instead of using the roller drive, it has conventional planetary gears. The clutch has the disengagement outboard of the gears, so the gears and motor don't rotate when free-wheeling. With the Bafang, the gears are still engaged and rotate slowly when free-wheeling. The rotor in the Q100 also runs much faster than a Bafang and is smaller in diameter - hence the smoothness and quietness. I hope this helps.

SWXU above and Q100 below

 

[shemozzle999]

Yes they run at double the speed increasing wear on the smaller gears.