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Electric Brompton – custom build

Discussion in 'Electric Bicycles' started by benjy_a, May 19, 2012.

  1.  
    benjy_a

    benjy_a Finding my (electric) wheels

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    Background
    Ok for those who haven’t 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 can’t 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 don’t 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 – 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 – 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 didn’t 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 it’s 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; it’s going to be quite heavy but still tiny...fingers crossed it works out how I want; watch this space if you’re interested.

    Ben.
  2.  
    benjy_a

    benjy_a Finding my (electric) wheels

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    The build has started; I still don’t 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.

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  3.  
    benjy_a

    benjy_a Finding my (electric) wheels

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  4.  
    cwah

    cwah Pedelecer

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    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: May 19, 2012
  5.  
    benjy_a

    benjy_a Finding my (electric) wheels

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    Hi cwah, thanks for the input...

    The controller is in this position because in my opinion it is the best place. The cable runs will all be very short, there is no interference with the fold in any way, I only need to run 2 wires from the bag (battery) and will be using the Brompton Nano system of contacts on the front luggage block. There will be no extra wind resistance from this; it's really not a concern on the Brompton as the riding position is completely upright in any case - the bike is totally un-aerodynamic at the best of times! :D

    Cellman uses cylindrical A123 cells.

    As I mentioned before, the Ezee warranty of min 60% after 2 years does not make it worthwhile for me. 60% of 14Ah will probably not get me to work so the battery could be useless to me and still classed as 'good' under warranty. The Cellman battery has a greater chance of serving me for longer, albeit with some risk if it goes wrong but that's a risk I accept.

    Sorry to hear about your problems with your Lyen controller; he has many satisfied customers and I hope I will be a bit luckier than you. Ed has been very helpful so far with great communicaiton; I guess time will tell. I'm not going to be pushing this controller particularly hard so perhaps that will also help.

    Ben


  6.  
    jerrysimon

    jerrysimon Pedelecer

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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: May 19, 2012
  7.  
    banbury frank

    banbury frank Banned

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    Hi benjy_a
    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

    Frank
    Last edited: May 20, 2012
  8.  
    eddieo

    eddieo Banned

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    Sorry but I cant see a bike like this working day in day out reliably.....
  9.  
    benjy_a

    benjy_a Finding my (electric) wheels

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    Good point Frank, I have another slightly larger aluminium box which I'll have a look at fitting.

    Sent from my GT-I9000 using Tapatalk 2
  10.  
    benjy_a

    benjy_a Finding my (electric) wheels

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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.

    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.

    Sent from my GT-I9000 using Tapatalk 2
  11.  
    eddieo

    eddieo Banned

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    I am not very technical, but read a fair bit about ebikes and know that even the best suffer failure from time to time. So I am kind of assuming and I dont think unfairly, that what looks like to me a fairly highly strung set up, will not withstand day in day out commuting. A back up bike solves this.

    I have had loads of problems over the 3 years I have had bikes, I dont commute on them so no real headache except when one failed on holiday in Italy...

    I would use a cheap petrol scooter for 10 mile return, and leave a cheap bike at other end for 3 mile journey...but this has been suggested before. Also I dont understand why an illegal build necessary. A 250 watt bike (with spare battery?) moves my unfit 18 stone more then adequately, and is probably a lot lighter and more enjoyable and comfortable to ride then your build.
    Last edited: May 20, 2012
  12.  
    benjy_a

    benjy_a Finding my (electric) wheels

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    This is not an illegal build. Motor is 250w, I have a 36v battery (39v) due to being Lifepo4. Controller is programmable and motor will not be more than 250w nominal.

    I have stated several times that this is to be limited to legal speed limit and power. There have been discussions surrounding the potential power output of this controller / motor combination but I have stated several times that it is to be kept legal.

    The whole purpose is to produce a folding electric Brompton which has similar electrical capabilities as say an eezee or Wisper which are at the top end of legal.

    I do not want a moped thanks, your comments about unreliability have no more bearing on this build than any other electric bike as far as I can tell. Any importer / bike builder must decide on which components to use and then set the bike up accordingly to be legal. The nominal 250w limit is a fairly moot point and almost impossible to measure. Ebikes vary hugely in power output depending on the circumstances / terrain etc the more important and easily measurable limit is the 25kph.



    Sent from my GT-I9000 using Tapatalk 2
    Last edited: May 20, 2012
  13.  
    eddieo

    eddieo Banned

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    No need to get shirty you asked for my thoughts and got them!lol What will it weigh?

    and I dont really get the need for a bulky 6kg battery when one way commute is 13 miles? assuming you can charge at work end...
    Last edited: May 20, 2012
  14.  
    banbury frank

    banbury frank Banned

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    Hi I think you have ordered some very good parts to make a super RELIABLE bike for commuting
    with full control with the cycle analyst

    If you limit the amps to 10 A and set the speed to 15MPH

    It will be fully road legal

    I was trying to help with the heat problem

    Every thing else looks Fantastic

    Frank
  15.  
    benjy_a

    benjy_a Finding my (electric) wheels

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    Sorry didn't mean to come across as shirty. The motor and controller will add about 4.5kg to the Brompton. The battery is heavy but will be in the removable front bag so won't add to carry weight.

    Sent from my GT-I9000 using Tapatalk 2
  16.  
    eddieo

    eddieo Banned

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    I hope it works for you but its probably going to be about 22kg...I still dont get why a bulky 6 kg battery required for a 13 mile commute running legally, it makes little sense to me. Established tried and tested, bikes with warrenty and a spare battery would do the job just as well...anyway good luck its all fun!
  17.  
    benjy_a

    benjy_a Finding my (electric) wheels

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    Thanks, I hope it will too. I want the range to be 15-20 miles, some of it quite hilly, using max assist as much as I want (all the way coming home). Has to be a brompton as it has to go on a commuter train. There is no such bike available commercially with a warranty, trust me if there was I would have bought one. :)

    The battery is hefty but this choice has been discussed at some length following advice gratefully received from others on this forum.

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    Last edited: May 20, 2012
  18.  
    benjy_a

    benjy_a Finding my (electric) wheels

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    Ok, time to get back to the build. Thanks to Frank for the pointer about overheating; I have now fitted a larger aluminium box to house the controller. This will of course conduct lots of heat away and also allow some air gap. I will paint it black, I don't think it looks too terrible or much more cumbersome than the smaller plastic box.


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  19.  
    benjy_a

    benjy_a Finding my (electric) wheels

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    Hi Jerry,

    Yes I concur totally! I have had to shave off just 1-2mm here and there from my control box mounting to get it to still fold. You really cannot plan for these little details, just have to adapt as you go.

    One of the main reasons for me wanting the control box on the handlebars is that I will only need to run 2 wires - the main multi core feed to the motor and the power from the battery. These will follow the brake cable route on the Brompron.

    Ben

  20.  
    bazwaldo

    bazwaldo Finding my (electric) wheels

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    This looks to be a very interesting project, thanks for posting about it.
    I recently sourced a LiFePO4 battery direct from China which was advertised as a 12AH size and so far using my full size Bearprint Ebike it is comfortably completing a 26 mile work commute on 1 charge usually with 3 sometimes 4 lights still showing after stopping at home.
    If you are charging the battery at work the 14AH battery may be "overkill" and you might be able to manage with a smaller perhaps 10AH battery.
    According to opinion on the forum though charging with more capacity left will prolong the battery life rather than draining it each time and then recharging.
    6KG is pretty heavy and a smaller battery might do your distance and be easier to carry.
    Good luck with your project.
    Barry.

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