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Newbie build report: BMC V4 50+ V. Parts, details, gotchas


1 µW
May 13, 2014
Dear Endless Sphere Community,

I would like thank you all from the bottom of my heart for accumulating amazing open information on these forums. I am really stoked about this technology and without you I would not be able to get anywhere. Thank you for existing and pioneering and advancing this amazing mode of transportation.

That said, the least I can do is share a brief story of my build, parts, details, and gotcha's for other newbies.


Oh and if you are in a TL;DR mood, here's the list of parts., in all kinds of formats! Includes BOM with some details, pricing, brief notes and comments.

PDF: https://dl.dropboxusercontent.com/u/13889588/ebike report 5-13-14/parts.pdf
ODS spreadsheet: https://dl.dropboxusercontent.com/u/13889588/ebike report 5-13-14/parts.ods
XLS spreadsheet: https://dl.dropboxusercontent.com/u/13889588/ebike report 5-13-14/parts.xls

My goal from the start was "fun, reliable, efficient and affordable commute vehicle". For me fun meant fast, unassisted 20+ mph fast, and reliable means taking daily 6 mile commutes without having catastrophic technological breakdowns. After scouting the Endless sphere forums and blogs for months I decided that a 48V battery and a geared hub motors can be appropriate for an efficient and relatively fast ebike.

The research process was a hodge podge of different ways to rummage the Internet. Started with obsessive research backed by understanding of electricity basics. Watched a bunch of youtube videos. Read a lot of articles. This one, for example, pushed me in the drection of getting a geared hub motor: http://www.electricbike.com/hubmotor/. Thank you, electricbike.com. Once I decided on the motor and the battery the urge kicked in to just order stuff and start working on it, let it sort itself out! Some mistakes were made as the result. Particularly, mistmatching connectors between the motor and the controller caused a lot of grief down the road, but this was also aided by general laziness while addressing the mistakes after they were made. Neither of the problems was fatal but some significant headaches could have been completely avoided if some obvious things were questioned. The following lessons were (re)learned by yours truly, and allow me to reinstate this for all newbies: 1) do your f***ing research! 2) don't be lazy, take your time to do things right! bandaids will only take you so far, the patched up mess will bite you down the road, and at the worst possible time. 3) you may spend a little more time and money than you think you will. Anticipate it and be ready to deal with it, should you venture into the endeavor.

Of course, I cannot write about the process without mentioning amazing help from Ilia of electricbikes.sf and Tyson of vesselbikes.com. Ilia and Tyson have both been extremely generous and enthusiastic about sharing their knowledge. Thank you both, if you are reading this. Ilia has helped a lot with choosing components and putting them together and providing some key pieces of gear I was missing. Tyson has done a professional job of the hub wheel build. Thank you Ilia, Tyson, and everyone else involved and getting involved in this amazing community.

I could go on forever rambling in my newbie post, but I think I will start going over the parts, going in some sort of logical progression, and hopefully the gist and details of the build will emerge. Keep in mind this is written from a newbie's perspective. I was helped by experienced e-bike builders but still made a lot of oopsies while ordering parts and putting them together, and I will try to include it all so others doing the same thing will know what to watch out for.



Motor: BMC V4 Torque

As was mentioned the electricbike.com article really made me lean towards the hub motor. I wanted to build a bike that was fast and not too expensive. Excellent climbing performance and general tags of speed and efficiency? Sign me up for a hub motor.

BMC V4 geared hub motor does deliver. Relatively quiet, reliable, plenty fast running at <50% rated current. Everything about it so far has indicated a well engineered product. Additionally it was, repeatedly, due to newbiness, exposed to misaligned or disconnected phases and randomly disconnecting Hall sensor signals (the phase current, though, was probably limited by programming to 50% of max rating). It survived all of this abuse with no signs of degrading performance. When everything is properly connected runs like a bee. Fast, quiet, relatively small, covert and not too heavy. Very reliable piece of technology, expecting it to last.



Rim, Freewheel, Spokes -> Hum Motor Wheel Build
Parts from: http://ebikessf.com
Built by: http://www.vesselbikes.com

Even if you ask someone else to build the hub wheel for you, like I did, there are still plenty of opportunities for silly mistakes!

Rim, freewheel and spokes were purchased from ebikessf.com store. Not being very experienced in the way of the bicycle I was not sure about trying to do the wheel build myself. Ilya referred me to Tyson of vesselbikes.com, who has done a professional job of putting all the parts together. The wheel build came out great. I had to do a small mod to the rim, because rim had a smaller hole, probably for Presta valve. I drilled into it to make it big enough for Schrader to keep things consistent with the other wheel. (Don't need to keep track of which tubes I have to purchase if I just stick to Schrader). What I didn't do was grind and polish the edges of the expanded hole, which probably contributed to a few mysteriously flat tubes down the road, especially in the initial absence of the inner liner. Also, due to my newbiness I did not specify the connector types for phase and Hall sensor wires when requesting the wheel build. As the result these ended up being all different from the ones on the motor controller, which delayed the bicycle build and caused a lot of trouble down the road. This seems like an obvious thing to check, looking back at it, but... live and learn, what can I say! In a hurry made some adapters to connect things, and those were pretty janky at first too. Once it was properly dealt with everything worked great. More than a month of regular use, the wheel looks and feels fine. The parts selected by Ilia are living up to the expected performance and the build by Tyson appears to be impeccable.


Torque Arm: 135° Angle Torque Arm for 14mm Axle

Torque arm was custom made in minutes by Ilia, who started with the off-the-shelf part that he cut and polished to fit my bike perfectly. What else can I say? The dude is awesome. Thank you, Ilia! No wheels are flying off my bike and everything remains tight, so I assume the torque arm works.


Motor Controller: Infineon 18 fet 4110, 36-75V, 60A
Controller: http://em3ev.com/store/index.php?route=product/product&path=38&product_id=83
Program Cable: http://em3ev.com/store/index.php?route=product/product&path=41&product_id=101

Seems like a no hassle controller. Of course, knowing that BMC should be run at 25A to be used reliably makes this 60A controller one of the overkills. There is an upside to this. Given that the motor has a large area for heat dissipation and that it is configured to run at ~40% of its current limit suggests that 1) the controller is expected to stay cool 2) the controller is expected to last. The controller does appear to stay cool - cool enough to be kept inside the EM3EV's neat triangle bag, where it fits snuggly right next to the battery. I have never observed the bag the be warm while riding it, but it remains to be seen whether extermely hot weather can cause issues or damage.

My newbie mistakes here were not paying enough attention to the connectors. On a whim I picked 5mm bullets for phase wires, without checking which kind is more common in the field. Fitting 5mm male connectors for the motor phases were actually included with my order, and had I paid any attention to the fact when ordering a wheel build from Tyson I would have avoided some major headaches later.

Programming of the controller was done by Ilia. Using the oh-so-great software to program the controllers is a bit of an arcane art, it seems. If you attempt to do it youself make sure to allocate a good portion of your time to figure it out.




Ignition switch: http://em3ev.com/store/index.php?route=product/product&path=38&product_id=83
Full twist throttle w/ cruise control: http://em3ev.com/store/index.php?route=product/product&path=41&product_id=94
E-brake: http://ebikessf.com/node/144

Ignition switch works straightforward. E-brake was also straightforward, once I got it. (Did not research enough when making my first order to know that e-bikes need an e-brake! doh...)

Full-twist throttle seemed like a good idea when researching. Later I had a chance to try an ebike with a thumb throttle and it seemed nice, and got me worried about full twist being a good choice. After using full twist for a month I am kind of used to it. When wearing gloves it is very convenient and gives you good control. Cruise control button provides a basic acceleration-based cruise control when plugged into to the motor controller. This works fine when going full speed by yourself, but you may be having a hard time trying to match the cruise speed with that of unmotorized cyclists you are riding along with. You will need a more precise cruise control setup to have a fine control of a velocity below the build's top speed.

Some experiences made me reconsider the safety of a thumb throttle. When riding properly the e-brake is the kill switch for any out of control behavior by the electric beast. In the event throttle remains twisted but e-brake remains unreachable you may find yourself struggling to get a hold of the situation. My experience with the situation happened while I was walking my bike next to me, thinking it was turned off. With its relatively light weight and no terrain or solid restrain to keep it grounded.. the machine can be quite impulsive. The outcomes are either... you get a hold of the situation, after a few moments of struggle, and have your fingers find the e-brake. -or- the machine darts off a short distance, before your fingers/whatever is holding the throttle get released and everything abruptly stops. That last part relies on the spring action of the throttle to remain in perfect working order, and I intend to keep my eyes on that thing. No issues whatsoever there, yet; fingers crossed. Going back to other types of throttle, I imagine them to be more safe, in general. I would love to hear what others have to say.



Battery: 50V 18.5Ah Samsung Triangle Pack from EM3EV (high discharge model)

58V top voltage battery from EM3EV. Another component I have learned to trust. This is a high discharge model. According to Ilia, to run BMCv4 reliably it should be run limited at 25A, 1/2 of the rated current. Which makes the high discharge model, even with its 40A BMS bottleneck, an overkill. However, due to it being a high discharge model it is expected to last longer as, in theory, continuous discharges at 25A should not qualify as abuse. I feel under-equipped and under-motivated to track the daily degradation of the cells for the moment. After a month of use the battery is still running strong, good steady discharge from 56V-50V. Never took it below 48V, but noticing slight decrease in power when taking it close to that range. I probably should do more research about how low the cells can and should be taken.

The frame triangle really is the best place for the battery. Sometimes I attach a milk cart to the bike rack and load it with groceries, which basically simulates having a battery there. It feels wrong. The bike feels a lot less stable, and at higher speeds a lot more dangerous. Heavy stuff should be low and in the center.


Battery charger: http://em3ev.com/store/index.php?route=product/product&path=35&product_id=123

Battery charger works well. Kinda loud, but doesn't take too long to charge. I spend ~5Ah on a typical commute. With this charger it takes ~1hr to charge the battery to full. The charger is rated for 5A, so 1hr x 5A = 5Ah, which is, roughly, the energy involved! Makes sense, I think.

The loudness is enough to make one conscious of it in an office environment. My office happened to be well ventilated, so I put my charger in the bottom of a drawer with only wires sticking out. The noise is significantly reduced. It gets warm but no signs of issues yet. There have not been failures to charge the battery. There have not been fires or a need to wait and let anything cool. Everything just works, and this is how I want my daily battery use and charging to be.



Tires: http://www.amazon.com/gp/product/B00AYA86ES/
Tubes: http://www.ebay.com/itm/400575173415
Tube liner: http://www.ebay.com/itm/190936586066
Inner Liner: came with the bike

Before actually trying an e-bike I thought one could get away riding racing bike tires on an e-bike. I now imagine that would be either really slow or really dangerous. Newbies, really do try an e-bike before buying parts! My hybrid bike's frame, though, would not allow for a tire much thicker than default 40mm thick. So I ended up with with a 700 x 43mm tires from Continental. (700C tired were suggested by Ilia to achieve higher speeds). The tires are good and relatively cheap. They wear slowly, expect them to last for months. If you have a random flat and find yourself drifting on your rear wheel the tire may get damaged. I don't do extreme mountain biking with my e-bike, and typically I spend most of the commute going at max speed on a well asphalted road. The tire can handle occasional offroading without issues, though I rarely go full speed when trying to offroad.

I had Sunlite tubes before. (company/brand was folrmerly called Pyramid, I believe). They don't pop easy and they last. I had a few unexpected flats on my rear tire though, when just starting to use the e-bike. Sometimes that happened when landing on the the rear wheel after a hop; other times it came out of nowhere. These probably happened because of not grinding/polishing a drill job on the rim. Once that was cleaned up, inner and outer liner installed, everything works great. Had no flats for a 1+ months. The outer liner (between tire and tube) is SpinSkins Duro - apparently an economic version of SpinSkins Race but still $35 a pair. They are very light, but don't know how much that matter when the bike itself is kinda heavy. Don't know how much better SpinkSkins Duro compares to a cheaper Mr Tuffy and such. I think I picked SpinSkins because I could not find mr Tuffy to match my less common 700C x 43mm tire size. Either way, SpinSkins seem to be working. No flats = happy rider.

Cycle Analyst 2.3: http://em3ev.com/store/index.php?route=product/product&path=41&product_id=103
Spoke magnet: $6 spoke magnet from a store



Cycle analyst is a solid piece of electronics. What it does it does well. One hurdle was matching the internal resistance of the controller, which was 0.71 megaohm, on the low side. While trying configure the CA with Ilia the device kept resetting resistance repeatedly when entering a low value. After perforing RTFM procedure it turned out there was a "high range" mode in Cycle Analyst, which means higher range of resistance you can input, and appears to result in more accurate current measurements when using low resistance. So, if you run into a problem... sometimes the answer is right there. In the manual. Read it. No one will judge you!




Rear Lights
LEDs: http://www.ebay.com/itm/221248178486
Enclosure: http://www.autozone.com/autozone/accessories/Blazer-2-x-4-in-red-bulls-eye-light/_/N-262p?itemIdentifier=377739_0_0_
Other materials: wire, hot glue, duct tape, double sided tape

Who doesn't like shiny lights! These were definitely on the very bright side, but it is better to be seen very well than not to be seen at all. Things were put together while inspired by a video by pendragon8000 where red star LEDs were used: https://www.youtube.com/watch?v=6twweNDAvKY. I was messing with these 3W star LEDs before and for the most part they are very resilient and not too picky on the power source. They don't burn out when connected directly to a battery, as long as you keep input voltage below 5V per LED. Instead of trying to come up with a decent enclosure myself I found a good fit in the form of a $3 garage door clearance light from Autozone. Default incandescent (eeew...) bulbs and holders were removed; only enclosure remained. I considered using tinfoil as a reflector to be placed behind the LEDs, but ended up cutting a small pad out of an old torn up sun shade for a car. The material holds shape but is also soft and a bit puffy on the non-reflective side. Stays in place by itself but even better with some hot glue. Star LEDs were attached to the reflective surface with double sided tape and hot glue around the edges. 6 LEDs are wired in series and connected 12V output from a voltage regulator in the front of the bike. The enclosure itself is waterproof so I was worried about LEDs getting toasty. So far there has been no problems with that, though I have not spent much time riding the bike in extreme heat. The LEDs are bright and powerful and they do get warm, but continued use shows no signs of heat damage, things melting and moving out of place, etc. Seems fine.





Front lights, 12V regulated power
Original headlight: http://www.ebay.com/itm/221367694932
Front light mount: Cycle Analyst Handlerbar Clamp
DC-DC converter: http://em3ev.com/store/index.php?route=product/product&path=41&product_id=90

Definitely an important component but I could not justify to myself spending $100 on a headlight. So I started with a $15 Chinese light off of eBay. Input voltage was advertised as 12V-60V, and it indeed worked well with my 50+ V battery. The default mount is not so great but Ilia sold me a Cycle Analyst mount and installed it. The light was bright and worked well, until... rain. The lights are not waterproof and sometimes I learn things the hard way. After a ride in the rain the front light stopped working. As I open it up to take a look I start to hear faint hissing. I lean closer and the hissing intensifies. By instinct I move my ear away right before a loud pop. A capacitor explodes right next to my ear! Darn! 15 minutes later the ringing subsided and I become reassured I'm not losing hearing in one of my ears. Upon a closer examination a rolled up tape shot out of the capacitor like a confetti tape. Cute, but not when terrified of becoming deaf.

So with the front light already opened up I begin experimenting with putting all kinds of stuff inside the enclosure. I replaced the explosive voltage regulator board with a 5mmx x 2.5mm x 1.25mm DC-DC converter from EM3EV. This regulator now supplies power to the front and rear lights at 12V, and is itself powered by the high voltage output of Cycle Analyst. The voltage regulator works great even after repeatedly shorting its output (doh!) Love components that can take some abuse! For the front light I have 3 of the original star LEDs in series. I sealed ventilation holes in the enclosure with hot glue and tape, leaving only a small horizontal gap at the very bottom of the case, likely a drain for dust in the original design. Cut a hole on the side and added a switch that turns front+rear lights on/off. I bought a $2 usb car charger but no matter what I did it would not fit inside the front light enclosure. So I removed the charger casing, hot glued all of the circuit board surfaces and covered it with tape. The charger is now squizzed in the gap in the mount below the lights, with some tape to keep it secured.

So there you have it, fellow makeshift engineers. $15 dollar headlight provides an excellent enclosure and LEDs. Add some hot glue, tape, $2 usb charger, $10 for DC-DC converter you have a rain-proof light with a usb charging port and enough 12V power to drive the rear lights. Don't use the unmodified headlight in the rain. Things will explode and can make you deaf! Seriously. Heating concerns still apply, as there are now 3 star LEDs and a voltage regulator inside a tightly packed enclosure. Nothing happened yet after months of use. Make sure to not put too much voltage on any star LEDs. Stay below 4V, you will be ok.



Sucky mirror: https://www.dx.com/p/oqsport-305d-quick-release-flexible-bicycle-rearview-mirror-black-258891
Decent mirror: http://www.ebay.com/itm/271251590982

Do not buy sucky mirrors. Spend a little bit more and get a decent handle bar mirror. Sucky mirrors will shift due to vibration while riding, becoming a pesky annoyance.



Sheathing: bought in ebikessf.com physical store

Sheathing is an excellent way to contain wire chaos involved in an e-bike. The one in the pictures is made from nylon, I think. You sometimes see it in computer power supplies and such. Working with sheathing pieces is very easy, but to cut them to the right size they have to be cut with a red-hot razor blade (If you do it be prepared for nasty fumes that get released). Ilia was the man with the tools and the know-how.




Smartphone holder: http://www.ebay.com/itm/Waterproof-Bicycle-Bike-Phone-Mount-Holder-Case-Mobile-for-iPhone-5S-5C-S4-Mini-/390666578331

This is a decent waterproof smartphone holder. Why not have GPS navigation on your ebike? One defect here is that the phone-holding part does not feel like it attaches very securely to the mount. A little bit of good tape makes it feel safer. (Yes, a lot of problems get solved with tape) The phone fits very snuggly inside the holder, but if you jam too many things inside like audio and charge connectors at the same time you will have problems. I did that and broke one of the zippers. Still, going to get another one of these smartphone holders and try to treat it better, or find better ways to get cables in there. Ideally there would be no audio cable and everything will be wireless. I dislike bluetooth due to weak audio quality. Wifi-based alternatives like AirPlay or similar will either be way more expansive or take some time be DIYed. For now I am stuck with an audio cable going to my smartphone.

U-lock, tire tool, spoke tool, riding gloves, etc.

If are new to bicycling in general these are very good to have.

Past issues:

Mismatching connectors between the motor controllers have caused a lot of grief (I ordered 5mm female bullets for the controller, and without specifying it ended up with 4mm male bullets on the motor). Initial workaround adapters were janky, were breaking themselves, fixed in a hurry, repeatedly, kept getting worse. Part of the problem was that there was barely enough phase wire length between the controller and the motor. The result was lots of tension that was pulling my adapters appart. Eventually I got really frustrated, arranged everything as neatly as I could and hot glued everything. This may not be a very exchangable setup in its present form but having motor connections getting loose during the ride is unacceptable.

Current issues:

Currently having an intermittent problem of motor briefly shutting off. It happens both when throttling manually and also when using cruise control, even when my fingers are nowhere near throttle or brakes. It tends to happen when going on rough terrrain or when going against a strong wind. My guess is vibrations cause e-brake to trigger momentarily, even with no fingers involved. It only lasts for a moment and I can resume throttling almost immediately. Just feels a bit interrupting.

Conclusions, lessons learned, curiosities:

- $3000 ebike is not going to save the world's transportation problems.
- It solves some of my transportation problems. Particularly it addresses the feeling of being a sucker to big oil when going to a gas station and swallowing the bullshit reality they work to maintain, ride after ride. The experience is now limited to 1.5 times a month, on average.
- One becomes curious about how much the vehicle would cost if it was put together in a place closer to India and China...
- The vehicle does fit excellently well somewhere between having a car or going everywhere on a bicycle
- People don't mind me taking it on trains where other bicyclists carry bikes. Most people don't suspect it is motorized. This makes my goal of low profile a success.
- It is very rewarding to put together a vehicle where every component can be traced and most things self-serviced or cheaply replaced
- It is waaayy cleaner and easier to keep running than a 2-stroke gas bike conversion. However, you lose the ability to annoy the entire block with your loudass BRRORWWWOOOOM ROOOOOOOOOMW. And lets face it, ebikes are a lot more expensive than gas conversions of equivalent power. Electric is the future, though.
- Overall the vehicle is very easy to maintain. Normally I pump some air into tires once a week. Because the bike's frame only works with brake pads I have to change those every now and then. Other than a mandatory recharge after every ride, that's about it. It remains to be seen how long it takes for the motor to show signs of wear, but having bought one from the super awesome store in the area makes me feel less dreadful of the wear. Spokes have not come loose yet, and neither have the nuts, washers, etc holding the motor. (Torque arm must be working)
- One caveat in maintenance is getting a flat in your (rear) hub wheel's tube. This will be punishing should it happen far from home/repairs station, especially in an unfamiliar environment. So far I have not ventured on the vehicle outside of a densely packed urban environment, which has provided means of carrying the fallen bird back home. Whatever adventures you are planning make sure you have a plan for either fixing all flats in the field or have a rescue ship bring you back to the mothership. Either way, to avoid flats utilize whatever heavy duty tube and liner you've got at your disposal. Take your time to install it right. You don't want to open those tires often.
- Generally speaking, try before you buy. Whenever you can.
- Do your research but also talk to people. They know things about technology that you don't find in spec sheets. This can save you a lot of resources and can result in a better, safer build.

That's it, hopefully someone finds this writeup interesting or useful. Lemme know what you think!


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crezzy2k1 said:
Nice write-up man!

Thank you! It took some time but once I got going I could not stop. Hoping to give at least a little something back to the Sphere :)
I agree, nice right up!.

Thanks for taking the time to put it all in writing. I got a lot of info out of it.