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Electric Brompton Ė custom build
Ok for those who havenít seen my other posts on this subject I need a bike to commute 10 reasonably hilly miles to a station, fold small enough to then go on a busy London commuter train and then take me another 3-4 miles at the other end to get to work. I want an electric bike to do this because I canít stand the thought of a 10 mile ride home after a 12+ hour night shift! Money constraints are not really a factor in this project (within reason) but I do not want to waste money on anything I donít need. I am planning on downgrading and possibly getting rid of the car completely if this works.
The ideal package (for me) is impossible with the technology available to me Ė i.e. a bike which is very light, folds as small as a Brompton and has as much power as the top end full size electric bikes on the market Ė maximum legal power; I do not want a light assist bike....what I want is a small, foldable electric bike which will fly up hills at the legal maximum speed and get me home with no fuss....it needs to do this reliably, several times a week and with a range of 15 miles (assuming a recharge at work).
So I quickly realised the sacrifice I had to make was in relation to the weight. I cannot go for a larger bike due to the constraints on the train so my project is based on a Brompton M3L folding bike. None of the kits or conversions available quite suits the bill for me. The Electric Wheel Company Nano Brompton does not have enough power for what I want; neither does the CH White bafang based conversion which I have ridden. I started to look for a supplier of the Bafang 8fun SWXK high RPM (300+) but failed miserably to find one; I had intended to run it with a higher power controller to spice it up but had to give up on this idea.
So...I turned to Crystalyte who have a kit for the Brompton on their website which is showing with the now discontinued 209 motor (this is the motor used in the US NYCE Wheels Brompton). However, I didnít like the look of the fact that it is supplied with a 12A controller and 9Ah battery which is just going to be far too weak and dreary and in fact worse than the Nano Brompton as itís so much heavier.
So; the Crystalyte G209 is the replacement for the old 209 and fits the Brompton forks without modification; I decided this is to be my motor but I will drive it significantly harder than 12A and with a battery to suit this. As its brand new there is nothing on the internet about this motor so this is a bit of a leap of faith to say the least. On the plus side, it is being delivered to me already built into an official Brompton rim by Crystalyte which makes things a whole lot easier.
I have gone for a Lyen Mini Monster programmable 30A controller with 3 stage power switch, throttle, cruise control module, PAS and Cycle Analyst (which I already have). This is to be set initially at 12, 16 and 20A on the 3 stage switch. The G209 motor should be able to handle high current easily as it is direct drive; at 30A it would theoretically be over 1Kw.
So, this setup will eat batteries when going up hill; I considered 48V with a speed limiter but ruled this out (with advice from others on this site) on the grounds of inefficiency. I have settled on Lifepo4 technology and have ordered an A123 Lifepo4 14Ah battery from Cellman (Emissions-Free) which weighs a hefty 6kg but has a nominal 39.6V which should give plenty of oomph. I have deliberated for a long time over this choice of battery but I am happy that it makes sense for what I am trying to achieve. It will have to withstand 2 charges per day, high current draw, possible deep discharging (depending on how efficient the G209 is!) and I want it to last as long as possible as it is of course expensive. I ruled out Lipo as I think it will just not last as long as I need...I seriously considered the Ezee 14Ah with 2 year warranty. However this warranty is for 60% capacity after 2 years...now 60% of 14Ah will just not be enough for what I need and 2 years is not really long enough for me to spend nearly £700 (as I need 2 chargers) on batteries.
I have also bought a Magicshine 808 bike light head and a DC-DC converter from Ed Lyen; I will have a nice 900 lumen light running from the main battery.
So...the build is soon to begin and I will post some pictures of how I intend to put all this together on the bike; itís going to be quite heavy but still tiny...fingers crossed it works out how I want; watch this space if youíre interested.
The build has started; I still donít have the battery or motor but I have started installing some components to the Brompton. Brake levers, cruise control module, 3 level power switch and throttle have all gone on the bike with few problems. I have fitted a box ready to take the Lyen controller and DC-DC converter. This is going to be a very tight fit but I intend to do away with all the connectors and hard wire everything to save space inside the box. I will attempt to post pictures....I have decided to locate the controller on the handlebars. This minimises cable runs and I think is the best place for it.
As you can see it's early stages but everything looks OK I think...none of the cables have been run properly yet.
Really nice bike on the brompton. I'm really keen on knowing how this G209 does perform. My actual conhismotor DD uses around 25wh/km... but I have crazy acceleration peak of 3000W. I'm trying to limit the max current because I can't really use my bike for very long with that.
Have you decided to put the controller in this position in order to cold it down? Because I think that if you go faster than 20 mph, you'll have quite a lot of wind resistance from the controller. But as you're only travelling at low speed it's probably not a problem.
And last point, for the battery, 6 kg does seem quite heavy for 39.6V14AH. You're at 92.4wh/kg. So just slightly lower than a ping. (around 97wh/kg). I thought cellman has the prismatic cells that are at 133wh/kg?
The Ezee battery pack offer is actually quite good. Don't really remember the price but just think that he is the only seller that propose warranty to its battery:
- Cellman doesn't propose any warranty
- Lyen doesn't propose any warranty
- Ping has 12 months warranty but you have to ship it back and the shipping cost is almost half the price of the battery.
When I received my controller from Lyen, it died within 30 seconds of cycling. I had to send back the controller to lyen and he charged me the shipping cost to send it to him, the repair cost and the cost to ship it back to him.
I'm quite upset with Lyen now, because for me the warranty was implied...
So I hope you won't have problem with your controller because quite a few people on endlessphere had had problem with his controller.
Anyway, that's really a nice start and I'm looking forward to see more on this build
Last edited by cwah; 19th May 2012 at 18:20.
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Ben looking good. Interesting we are both doing conversions on our Bromptons. I am looking for 5+ miles one way ultra light carry weight of the bike with very light assistance for in and around the pretty flat terrain of Cambridge, whereas you are looking for something that will take you 14+ miles and power you up hills.
The real challenge I am having during the build, is to make sure nothing compromises the fold. Just a new part or a wire in the wrong place and the whole fold is jeopardised
Its only when you do stuff like this, you realise just how thought out every detail is and how well the Brompton design is right down to the cables runs and their positioning on the bike!
Last edited by jerrysimon; 19th May 2012 at 22:00.
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You need to look at the controller in the box there is no way for the heat to dissipate It will cook the controller it will probably MELT the plastic box As you are going to do 10 miles in one run It has time to heat up
If you cutout large windows and line with a fine mesh it may work
Sorry to be the bear a off bad news it looks so neat
Last edited by banbury frank; 20th May 2012 at 06:57.
Electric bike Suppler
Conversion kit specialist
Sorry but I cant see a bike like this working day in day out reliably.....
Good point Frank, I have another slightly larger aluminium box which I'll have a look at fitting.
Originally Posted by banbury frank
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I have to say this is a particularly pointless point to make :banghead:.... I would love constructive advice as I have had from others.
Originally Posted by eddieo
Just saying it's going to be unreliable doesn't really mean anything. There's no reason for it to be any more unreliable than other electric bikes with high quality components.
I look forward to hearing your reasoning behind your comment.
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