Electric Brompton – custom build

[jerrysimon]

Thanks great to read and see the pics.

Weight wise, its the penalty you have to pay to meet your requirement.

The wiring always takes ages. Plus I have found that although you test everything before you finally solder up and heat shrink, some other problem often results.

I also relate to all the motor spacing issues though mostly I have had sufficient room on the motor shaft to fit the required spacers. Also imagine how I felt when I had to spread the forks and file out the dropouts on my £275 Ti forks!

PS

I also have regenerative braking activated on this controller. I’m not too bothered about the extra little bit of range this will create but I am super impressed at the actual braking sensation. As it kicks in I get a nice gradual reduction in speed without having to cause any wear to my brake blocks or rims...if I need to stop quicker I just squeeze harder to activate the actual brakes. Brilliant!

I read I think on endless phere that regenative braking really isn't worth it AND that it puts more reverse torque on your dropouts so a good torque arm setup are essential!

Regards

Jerry

 

[benjy_a]

@Jerry,

Re the regenerative braking I'm in two minds about it. I am paranoid about the wheel nuts loosening and I'm checking every couple of miles at the moment.

There are 3 programmable levels of regen braking on the controller and I have is set to minimum which is really very mild...I will continue to monitor the situation though. My instinct is that its not putting that much stress on anything.

Ben

 

[benjy_a]

Ok I have just completed an 18 mile ride on the Brompton and I have managed to get the Cycle Analyst displaying somewhere near correctly. I can say that this motor is nowhere near as uneconomincal as had been expected. My old Juicybike battery managed the 18 miles and is still at 37.5V and much of the ride was uphill and against a strong headwind (maintaining 14mph up some pretty significant hills). I think I will have a range of a good 30 unassisted miles with my 14Ah battery.

I am using about 15-18Wh per mile; even with the controller programmed to 20A max the motor only twice peaked at that level (when accelerating from a standstill). On the flat (unassisted) it seems to draw about 2-3A increasing to about 10A on reasonable hills. This is no worse than the Bafang on my Juicy Bike. I think that this motor is a great improvement on the old Crystalyte 209 which was very inefficient from what I read.

So...if you don't mind the weight and drag of direct drive, this motor seems to be a fairly good solution for the higher performance electric Brompton.

 

[benjy_a]

I have now completed a fair few miles on the Brompton and I'm not entirely happy with the security of the motor in the axle. On the left hand side of the fork, the mount for the mudguard and the clip which holds the bike together when folded go onto the motor shaft. I see this as a problem for at least three reasons:

1) There is barely enough shaft to get the nut on properly.
2) The design of the wire clip on the shaft is such that it restricts the torque you can safely apply to the nut.
3) There is insufficient space to fit a proper anti-rotation torque washer.

I intend to re-mount the fold clip/mudguard bracket onto a stanless steel strip that I plan to attach to the fork leg with a strong, stainless steel T-bolt hose clamp. I considered riveting to the fork but I don't want to weaken the fork in any way. Removing this bracket from the axle will allow me to fit proper, strong steel anti rotation washers. I will post pics when completed.

Ben

 

[benjy_a]

I have now removed the fold clip/ mudguard mount from the front axle and mounted it onto a small piece of stainless steel. This is in turn attached to the fork very firmly with a t-bolt clip. As you can (hopefully) see from the pictures this has now enabled me to fit the nut onto the axle properly and I have also added a further anti-rotation washer to this side. I am now far happier that the motor is actually going to stay on the bike!

 

[benjy_a]

Electrical contacts have also now been added to the luggage block and bag frame so no wires to plug in...just attach the bag and off I go!

I did a first practice commute run today; 10 miles to the station in 36 minutes, average speed of 16.6 mph which I'm very happy with considering this is still with my old battery which really struggles up the steep hills.

The last stage in the project is the Cellman lifepo4 battery which I am still waiting for...really looking forward to finishing the project and using it daily!

 

[jerrysimon]

Good job Ben. Are you going to put a rubber cover over the nut ?

I guess its a different size to other stock kits that come with them ?

Regards

Jerry

 

[benjy_a]

Good job Ben. Are you going to put a rubber cover over the nut ?

I guess its a different size to other stock kits that come with them ?

Thanks Jerry...I do have some rubber covers but both sides interfere with the fold in different ways...both also would make the folded bike wider and I don't really see the benefit of them other than aesthetics. Is there any chance of water ingress through the threads?

Ben

 

[daniel.weck]

That's one hell of a front-heavy Brompton!

I now mostly ride with the lightweight Tongxin + A123 (2.3Ah) kit, which puts all the additional weight at the front, but with my alternative 8-Fun (Bafang) + LiFePo4 (10Ah) kit, I positioned the battery on the rear (inside a rack bag) to balance the weight distribution. This results in a safer, more predictable ride.

Well done with your DIY efforts though, keep us updated!!
Cheers, Daniel

 

[benjy_a]

That's one hell of a front-heavy Brompton!

I now mostly ride with the lightweight Tongxin + A123 (2.3Ah) kit, which puts all the additional weight at the front, but with my alternative 8-Fun (Bafang) + LiFePo4 (10Ah) kit, I positioned the battery on the rear (inside a rack bag) to balance the weight distribution. This results in a safer, more predictable ride.

Well done with your DIY efforts though, keep us updated!!
Cheers, Daniel

Haha yes it is indeed very front heavy. I don't have a problem with the handling but I do have to be very wary about potholes (even more than on a standard Brompton). I use a Brompton rear rack bag to carry all my daily stuff so its a bit more balanced than it looks. The lifepo4 battery I have on order will add even more weight but should make the bike go really well.

There is no denying that this is a heavy beasty of a Brompton but it seems to be doing what I need it to so far.

 

[benjy_a]

So I now have over 500 miles on the Brompton and wanted to give an update as to where I am with it.

With regards to the top speed and performance...the G209 I have found is actually very slow as supplied to the UK. I know that I previously said I was happy with the speed at 36v but I have changed my mind. The reason for this is that I have been running the programmable controller at 120% which has given me around 15.5mph on the flat and good hill performance which was perfect for me.

I have now discovered that it is very bad for the controller to run like this all the time. Apparently it stresses the electronics very badly and also runs very inefficiently and the 120% setting is intended as a short burst function which is not how I'm using it.

So...I have programmed it back to 100% to protect reliability and the performance is woeful considering the weight of the setup. I would be be better off with the Nano motor which probably gives a similar performance without the weight penalty. Basically I think that Crystalyte has wound the motor too slow for a 16" wheel at 36v and standard 100% controller duty; it would probably be fine in a 20" wheel.

So....my solution...I have upgraded my Cellman battery order to 48V. I will limit the speed (if I need to) and current to remain road legal but I will be able to run the controller at a more efficient 100% duty. I anticipate using a peak current of 5-10A which will also reduce heat in the wiring etc.

I will of course update fully when I get my new battery in a week or so...the project continues!

Ben

 

[cwah]

Some guys on endlessphere do use 120% frequently:
Endless-sphere.com • View topic - 120% on lyen program 3 speed switch.

No report yet of blown controller from the 120% setting.

 

[benjy_a]

Some guys on endlessphere do use 120% frequently:
Endless-sphere.com • View topic - 120% on lyen program 3 speed switch.

No report yet of blown controller from the 120% setting.

This is the advice from Ed Lyen himself....I'm not risking it as I need absolute reliability on my commuting machine.

"Here is the answer to your question on the 120% setting:The controller forces the MOSFET transistors to switch on and off faster than usual. It will cause much more stress to the MOSFET. You so only consider to use it like a turbo charger for the engine. It is like having the turbo charger spinning at over 10K RPM. "Boosting" is continuously will have the potential to cause premature failure."

 

[benjy_a]

My new torque plates....custom made by local metal worker. They cut the slots too long but I'm happy that the axle has no chance of twisting out now...the plates look very strong and there is absolutely no play in the width.

 

[benjy_a]

 

[shemozzle999]

Hi benjy_a,
It is a shame they made the slot too long.
If you removed one of the spacer washers it might be better if you mounted them on the other side of the fork .
You would have to manually spring the forks to get the locating pin on your plate to fit in the hole in the fork.
The advantage of doing this is if the nut comes loose your torque plate will still be clamped in position and hold the wheel in place (if the slot was the right length).
Either way your addition is a good thing and a must do for Brompton conversions - well done!

p.s. If you ever get some more made with the right slot length I would be interested in buying some.

 

[benjy_a]

Hi benjy_a,
It is a shame they made the slot too long.
If you removed one of the spacer washers it might be better if you mounted them on the other side of the fork .
You would have to manually spring the forks to get the locating pin on your plate to fit in the hole in the fork.
The advantage of doing this is if the nut comes loose your torque plate will still be clamped in position and hold the wheel in place (if the slot was the right length).
Either way your addition is a good thing and a must do for Brompton conversions - well done!

p.s. If you ever get some more made with the right slot length I would be interested in buying some.

I agree it is a big shame...it was one of those awkward situations...nice old guy, local business and I didn't feel right to demand he re-make them from scratch; I also did not really feel like paying to have some more made. Perhaps I'm just too polite but there you go...

Having said that I don't think the wheel is going to fall off. I regularly check the wheel nuts as I am paranoid anyway. I will be using regen braking when I get my lifepo4 battery so will be checking every journey for a while. The wheel is also never off the ground, always has (a lot of) weight on it so again; will not drop out of the forks even if the nuts come loose.

So for now I've decided to live with them as they are. I will get more made correctly should things ever move. At least I am comfortable that I have averted the primary danger of torquing out the fork dropouts. Incidentally I thought about putting the plates on the inside but it's not practical. You would need to bend the forks a lot to do this because the pin at the top is chunky and goes all the way through the fork. This would be a nightmare to remove for a puncture so better on the outside overall.

If I get some more made I will let you know, but these are for the Crystalyte motor which has a 7.5mm flat section.
Ben

 

[shemozzle999]

I agree, look after your supplier, they are hard to find nowadays.
Let us know how you get on with them.

 

[benjy_a]

Cellman battery has arrived...it's extremely well made. I have no chargers for it yet but I have taken it for a quick test as it has some life in it. First impressions are pretty awesome. Unloaded speed with controller at 100% is about 20mph which translates to 15-17mph on the road. I will have to play around with the current setting when I get the charger....I think 10-12A (peak) will be about right to remain legal and give great performance.

This battery is 728Wh which should easily give me 40-50 miles range even using constant full throttle in this very hilly area!

As you can see it fits in the rear pocket of the Brompton C bag perfectly.

For size comparison (hands are fairly standard size )

 

[jerrysimon]

Wow that is some looking battery. Nice sizing for the bag. Is it made of of pouch or A123 cylindrical cells ?

Regards

Jerry