Commuter bike planning/build thread

jmz

100 W
Joined
Jan 16, 2015
Messages
105
Location
Christchurch, New Zealand
Hi people, I'm making this thread to document the planning and construction of my first electric bike build, and to seek input on the design.

The candidate bike is this one here, a 700C commuter with a 19" frame, a Suntour swing shock fork, and dual mechanical 160mm disc brakes. I've had it for a few years, and I quite like it, the light weight and short frame contribute to snappy handling.

https://imgur.com/a/7sQle

I want to convert it for electric commuting. The roads are flat almost everywhere here, and my regular commute is 5km, so I do not require extreme speed, power or range, though more capacity than required for just the commute distance would be nice (and nicer on the batteries), as would extra torque for bike trailers.

As for relevant experience, I work as a power electronics engineer, so I have access to a full mechanical and electrical workshop, as well as all the high performance MOSFETs I could ever need.

My initial plan is for a 201rpm Cute Q100 build, running at 44-48V using hobby LiPos for a high discharge capacity relative to the small pack size I will realistically need, and get my existing rear wheel rebuilt with the motor. The multi-kW off road bomber will have to wait.

The big unknown is the controller. I am open to either COTS or DIY/open-source controllers, is there much of a consensus on the benefits of FOC for these small motors (i.e. will it enable higher powers/efficiency/effective bus voltage)?

Could possibly look at using a cheap OTS controller to start with, then experiment with rolling my own later. Other advanced considerations include integrated charging and monitoring, and also perhaps mechanical modification of the motor for heatsinking.

Does it look like the 160mm rear disc brake will present any problems with a Q100 motor? The space between the dropouts is 140mm, though I hear these can be pried apart some if required? I could take it as an opportunity to swap them out for some larger hydraulic brakes.
 
jmz said:
I've had it for a few years, and I quite like it, the light weight and short frame contribute to snappy handling.
If you really like it as a pedal bike, you may not want to convert it, but might want to find a second one or a similar one to convert instead. It may not ride the same after conversion, depending on what you do with it.

With a really small/light motor, pack, and controller, it may be close enough, but the bigger/heavier stuff you put on it, the less responsive it's handling will be.

Just a heads up from someone that's worked his way up from regular bikes thru bigger and bigger and heavier stuff, until now I ride the red monster CrazyBike2 that definitely doesn't ride well without it's motors. ;)


and get my existing rear wheel rebuilt with the motor.
I'd recommend keeping your existing wheel as-is, and building a new wheel with similar or identical rim/tire, so you can swap it back in if you need to (or want to, for comparison or any other reason).


I don't have any specific info about the Q100/etc., though--but there are several threads and posts about builds with them and/or discussion deciding whether or not to use such.
 
The Q series motors are a bit temperamental when it comes to choice of controllers. Stick with one that's known to work.

Personally, I wouldn't mess about with lipos. Those downtube batteries make a much neater installation and don't cost much; however, you always get caught in no-man's land between sped and power. 12S lipos puts you in the sweet spot.
 
I like the q100 motors. The q100H will give you about 30% more torque.

If you want a really small/light pack then a couple 6s 5AH lipos could be good for you. I recommend that if you are already getting a q100, just get the compatible controller from BMS. If you really want to go nuts you can upgrade the fets yourself, but I doubt you'd ever need to. 12s and a stock 15A controller will be plenty for that little motor.
 
jmz said:
Hi people, I'm making this thread to document the planning and construction of my first electric bike build, and to seek input on the design.

The candidate bike is this one here, a 700C commuter with a 19" frame, a Suntour swing shock fork, and dual mechanical 160mm disc brakes. I've had it for a few years, and I quite like it, the light weight and short frame contribute to snappy handling.

https://imgur.com/a/7sQle

I want to convert it for electric commuting. The roads are flat almost everywhere here, and my regular commute is 5km, so I do not require extreme speed, power or range, though more capacity than required for just the commute distance would be nice (and nicer on the batteries), as would extra torque for bike trailers.

As for relevant experience, I work as a power electronics engineer, so I have access to a full mechanical and electrical workshop, as well as all the high performance MOSFETs I could ever need.

My initial plan is for a 201rpm Cute Q100 build, running at 44-48V using hobby LiPos for a high discharge capacity relative to the small pack size I will realistically need, and get my existing rear wheel rebuilt with the motor. The multi-kW off road bomber will have to wait.

The big unknown is the controller. I am open to either COTS or DIY/open-source controllers, is there much of a consensus on the benefits of FOC for these small motors (i.e. will it enable higher powers/efficiency/effective bus voltage)?

Could possibly look at using a cheap OTS controller to start with, then experiment with rolling my own later. Other advanced considerations include integrated charging and monitoring, and also perhaps mechanical modification of the motor for heatsinking.

Does it look like the 160mm rear disc brake will present any problems with a Q100 motor? The space between the dropouts is 140mm, though I hear these can be pried apart some if required? I could take it as an opportunity to swap them out for some larger hydraulic brakes.
Your commute requirements are minimal and a mini-motor system will work fine. There is no need to over-complicate.
My two mini-motor powered bikes have gone though numberous revisions over the years and the trend is to simplify each time.
Things I thought were necessary in my first builds, like Cycle Analysts, watt meters, fuses, big battery packs, custom balancing harnesses, etc., I have found not to be needed.
Here are is a list`of observations of general mini-motor builds and some of them Cute specific.
1)For under 900 Watt systems, frt. mounted minis work very well. They don't make enough power to cause traction problems.
In the same vein, low power allows safe mounting in regards to the fork drop-outs. I don't even use a torque arm with my quality, alloy, MTB forks.
2) If you are set on rear mounting, go with the CST, which allows the retention of the donner bike's cassette. The DNP free wheel is rather kluncky shifting and it seems to be a shame to put a heavy set of gears on a sm. lite motor.The mounting width of the CST is 137 m/m(w/ a 9-speed cassette) and the wheel requires much dishing to center.
Motor selection for your bike;
A number of considerations here. The CST is either fast(328) or slow(201) wind. The 201 in a 700 wheel on 12S will top out around 34 Kph.
A Q100H(260 wind) will top out around 39 Kph and if you truely have no "killer" hills to contend with, this is what I would recommend. Since this is not available in CST form, it would be a frt. mount. One nice thing about the BMS Battery Q100H is, it is black, which would match your bike better.
Vendors? Sort of depends on which controller. The BMS Battery sine-wave controllers are nice, but with a Q100H and 12S lipo, there are some issues. First off, they will not reconize the Voltage of 12S, making the "battery gauge" and LVC useless. Also, the Q100H will benifiT from slightly higher current than the standard Cute, 20 Amps vs the 15 to 17 Amps normaly applied to the regular Cute. The SO6S is a soft 15A and the very large S12S is 23 A. If your intent is to use PAS as primary mode, it might be worth it to work around these problems with the S12S, as the sine-waves work very well with PAS.
If PAS is not your intent, I would recommend changing vendors and go with this kit;
http://www.elifebike.com/peng/iview.asp?KeyID=dtpic-2011-43-GR8W.234ME

Specify this controller;
http://www.elifebike.com/peng/iview.asp?KeyID=dtpic-2014-3K-SPSC.5TSNR
with the 810 meter. It is not the fancy display like the SLCD-3, but is has cruise, 3-speed switch, a perfect LVC for 12S(41V) and on/off switch. Unforunately, the "H"(called the "F" by Elifebike is only available in silver).

Batteries; Turnegy 6S 5000 mA from Hobbyking are the ones to use. You should get at least 4. I would keep it super simple and use a pair at a time. 5000 mA will take you close to 10 miles with moderate pedal and you can carry the other pair to switch on longer rides. The advantage to using only a pair at a time is, you can easily take them out to charge and if you do hit the LVC, you can swap and know you have the exact same range to get home. Also, our fav. 12S charger(the Thunder 1220)may be cost prohibitive to ship to you and you will probably have to use a 6S + 6S charger from HK. Also, from HK, you can use the 14G silicone wire(easy to work with, especially with 4 m/m bullet connectors)with this low-power system. Add a $5 2-wire Voltmeter from Ebay.
Look for a bag to utilize your center space, the standard large bag may be too big for your 19" frame. Put everything, batt.s, controller and extra kit wire in the bag for a very neat install.
Any questions, feel free to ask.

Note, if you go with PAS, make sure you order the Hidden Wire Sensor.

PS, there will be no disc clearance issues with the Cutes and going from a 12S/1P to a 12S/2P pack does not increase the "torque. The advantage of a larger pack is it is easier to keep the cel discharge levels more moderate. If you use a LVC of 41V, this will stop to discharge at 3.65V, right before they start to go wonky and stray.
 
Excellent information, thank you.

I'm not after PAS, a half-throttle would be ideal. Front drive is also acceptable.

I'm a little confused about the nomenclature used by the vendors. Elifebike specifies the following:

36V-261rpm-silver
24V-261rpm-black

Is the 'black' version a 1/3 faster wind then? The silver one at 36V-261rpm is the equivalent of the 261rpm Q100H then (standard to rate no-load rpm at 36V?)? Is its power-handling ability on the same level as the Q100H? Are either of those controllers programmable/adjustable?

The 4x LiPo suggestion seems good, if I can afford it (which is to say, if HK will ship to NZ)
 
Yes, the 24V Q100H would be faster than the 36V version, too fast for the 700 wheel.
And yes, the Q100H and and the Q100F are the same motor.
The controller with the 810 display has a 3-speed setting. With my 328 in a 24" wheel @ 12S, that works out to 23 Mph, 19 Mph and 16 Mph. The cruise works in any setting. These are very nice controllers, very smooth and quiet. Mated with my Cute, the system is dead quiet.
Make sure they know you want the 19 Amp/500 W controller, as the 17 A/ 350 W unit would be the default with this kit.
Or you could order the 500 W box and keep the 350 W one for a spare. If you are going to have a spare, it should be a controller. Use one of the extra power wires from the controller to power the Voltmeter and it will turn off at the handlebar mounted 810 display. A mini Voltmeter can be velcro mounted anywhere, even on the center bag between your legs. The "gas gauge" on the 810 display will not read correctly with 12S.
To deactivate the cruise, you might want to use one of these;
http://www.elifebike.com/peng/iview.asp?KeyID=dtpic-2014-19-JMEJ.3MWYN
I prefer the thumb throttle and just 'flip" the lever to cut the cruise. Safe enough on low power.
Speaking of power, the "H" w/ a 19 A controller will not be a slug. From a standstill, it will spin the wheel in gravel or on wet pavement if the throttle is wicked open, FUN.
Hobbyking ships everywhere, and you will need them. Aside from the batteries and maybe a charger, you will want a meter of #14 wire and a couple bags of 4 m/m connectors. The center bag is important IMO. Otherwise, you will have loops of extra kit wire exposed and after awhile, you will want to shorten them and that means changing out all the connectors which leads to.....save all that for your next build :D If you place both the controller and the batteries in the bag, the only external wire runs will be the Phase/Hall motor cable and the throttle wire. Very stealthy.
Lastly, be aware that you will have to file the drop-outs slightly deeper to fit the motor, and that means you will never be able to to back to the stock wheel. That is true with 99 % of the hub motors.
 
It looks like HK will only ship LiPo <4000mAh to NZ.

Does this suggest something like a 2s2p 3000mAh 6s combination? The flexibility of more packs might be good, but also getting a little unwieldy.

Is there a recommended charging solution for 4x 6s packs at once? (5A charging for 1C max charge rate?), or alternately just 2x ?
 
This seems like it would do the trick, however I'm not sure what the deal is with the balancing connectors and external balance boards. Does a 6s balancing connector not fit directly into these?

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10327
 
Rather than mess about with lipos, what about getting the 201 rpm Q100H and a 48v battery. The cost is nearly the same, and you'll get a neater installation. Speed will be about 20 mph with good power. It'll go a bit faster than that, but power will drop off. The 260 rpm one would be a bit to fast with a 48v battery at about 26 mph. The motor is too small to hold that sort of speed, so it'll get hot and so will your controller. It's even a bit marginal with 12s. It's very important to match the speed and power of the motor. You can't expect to get more speed by just getting a faster winding. If you have a lightweight bike, you're light-weight and you like to pedal very hard, it can still work. This is the battery:

https://bmsbattery.com/ebike-battery/685-48v10ah-bottle-09-e-bike-battery-charger-battery.html

Don't underestimate how useful PAS is. It only takes a couple of minutes to fit the sensor, so it's not a lot of trouble. There's a new type of PAS sensor now that clips in the BB on the left side.

https://bmsbattery.com/ebike-kit/705-dual-hall-sensor-12-signals-easy-assembling-pas-ebike-kit.html?search_query=pas&results=61
 
jmz said:
It looks like HK will only ship LiPo <4000mAh to NZ.

Does this suggest something like a 2s2p 3000mAh 6s combination? The flexibility of more packs might be good, but also getting a little unwieldy.

Is there a recommended charging solution for 4x 6s packs at once? (5A charging for 1C max charge rate?), or alternately just 2x ?
You can make a 2S2P pack using (4) of these;
http://www.hobbyking.com/hobbyking/store/__21358__ZIPPY_Compact_3700mAh_6S_25C_Lipo_Pack.html

That would be 12S/7400mAh-That would be good for 8 to 14 miles, depending on how fast you go and how much you put in with your legs.
Not the best bang for the buck though.

The only affordable balance charger that is currently available is this one:
http://www.hobbypartz.com/75p-1220-charger.html
I don't know about shipping to NZ.
Otherwise, you would have to split your pack to use a 6S + 6S charger. It doesn't matter about the Ah's, so you don't have to break the parallel connection.
At this point you might want to think about a different chemistry. I'm strickly a Lipo guy, so I'm not sure what to recommend.
You might search the post's of D8veh. He has recently switched from Lipo to building packs with cells from BMS Battery.

Edit;
D8veh posted while I was Typing, so you might want to take his advice, on the battery anyhow.
I don't totaly agree on the speed winds, but I guess everybody's experience is different.
 
Seems reasonable. So, all up, something like:

https://bmsbattery.com/ebike-battery/685-48v10ah-bottle-09-e-bike-battery-charger-battery.html

https://bmsbattery.com/ebike-kit/630-q100h-36v350w-front-driving-ebike-hub-motor-ebike-kit.html (201rpm)

https://bmsbattery.com/ebike-kit/705-dual-hall-sensor-12-signals-easy-assembling-pas-ebike-kit.html

https://bmsbattery.com/ebike-kit/552-s12s-500w-torque-simulation-sine-wave-controller-ebike-kit.html

can you simultaneously use PAS and a throttle on these just fine?
 
Looks good, at least you will get the black motor :D
Can't answer your PAS question, but remember, you will want the hidden wire sensor.
And if you are going to build your own wheel, you might want to get the spokes and spoke wrench from BMS Battery and source the rim locally.
I like the Alex rims.
 
Reading up on the S12S, what is up with the requirement for a speed sensor? Shouldn't that be entirely redundant if the controller is getting signals from the halls, as well as knowing the pole count/reduction ratio? I have a magnetic reed sensor already hooked up for my cycle computer if that is required to be repurposed for this (according to the manual it can handle 1 count/rev?)

What about S-LCD3 vs S-LCD1? BMSbattery notes somewhat ominously that "Not all parameters can be set by S-LCD3. Please leave us a message on which parameter you want to set."

d8veh, have you tested that particular PAS sensor with the S12S? (https://bmsbattery.com/ebike-kit/705-dual-hall-sensor-12-signals-easy-assembling-pas-ebike-kit.html)
 
jmz said:
Seems reasonable. So, all up, something like:

https://bmsbattery.com/ebike-battery/685-48v10ah-bottle-09-e-bike-battery-charger-battery.html

https://bmsbattery.com/ebike-kit/630-q100h-36v350w-front-driving-ebike-hub-motor-ebike-kit.html (201rpm)

https://bmsbattery.com/ebike-kit/705-dual-hall-sensor-12-signals-easy-assembling-pas-ebike-kit.html

https://bmsbattery.com/ebike-kit/552-s12s-500w-torque-simulation-sine-wave-controller-ebike-kit.html

can you simultaneously use PAS and a throttle on these just fine?

The PAS works like a sort of cruise control. Whenever you're pedalling, you get the power level that you set in the display from zero to max. At any time, you can use the throttle, which takes over from the PAS as soon as you operate it.

The S12S is a little too much for the Q100. If you use level 5 or full throttle at low speed, you could damage the motor. It could be possible to cut the current down in the advanced settings, but nobody has yet reported whether it works.

As well as the stuff in your list, you need:
A throttle. I prefer the plain thumb throttles.
A LCD. The S-LCD is the nicest.
A wheel-speed sensor.

I've been using the BMSB ready built wheels for years. I've never had a problem with them. I believe that they're perfectly adequate and it saves a lot of messing about finding the right spokes, etc; however, you have to finish off the spoke tensioning. They only seem to do a loose build, which you can't use until you've tightened all the spokes. If you order a complete wheel, the shipping cost goes up quite a lot.

The controller can get a speed signal from the halls, but the motor free-wheels, so you'll see the speed as zero whenever you go downhill or are otherwise coasting.
 
Yea I really wish they'd hire a dedicated wheel builder. That seems to be their weak link. I often get wheels with a couple spokes rattling around. I love their parts, prices, service and packaging, but not their wheel builds.

If people don't know that they need to properly tension their spokes then I can imagine people would have problems after a while with wheels getting very out of true or even broken spokes from uneven tension causing large loading on a few spokes. Throw in the spoke wrench, I think it's only $1. Best deal in town :lol:
 
Because of the extra shipping cost that would add to a shipment to NZ (looking at ~150 already not including a wheel), I was planning to get my existing front wheel rebuilt locally, using my existing rim. I should be able to pay less than the extra shipping, and get a better result. My front wheel's hub is on its way out in any case, too much off-road use I think, but the rims are still in great condition.

According to the S-LCD3 manual, parameter C5 can be used to limit current to a fraction of the maximum available controller current, so I'd rather have the ability to oversize the controller (for reliability and efficiency). Unsure at this stage whether this refers to phase current or controller draw. I also plan to investigate the use of oil cooling with ATF, these motors seems to respond quite well to it.

Still haven't heard from anyone if this part (https://bmsbattery.com/ebike-kit/705-dual-hall-sensor-12-signals-easy-assembling-pas-ebike-kit.html), the 12-count PAS sensor, is known to be compatible with the S-series controllers?

Many thanks, build looking good!

https://i.imgur.com/qy4p4WJ.png
 
jmz said:
Because of the extra shipping cost that would add to a shipment to NZ (looking at ~150 already not including a wheel), I was planning to get my existing front wheel rebuilt locally, using my existing rim. I should be able to pay less than the extra shipping, and get a better result. My front wheel's hub is on its way out in any case, too much off-road use I think, but the rims are still in great condition.
<<<<I believe your orginal rim is not suitable for ebike usage. Aftermarket double-wall rims are not exspensive. >>>>

According to the S-LCD3 manual, parameter C5 can be used to limit current to a fraction of the maximum available controller current, so I'd rather have the ability to oversize the controller (for reliability and efficiency). Unsure at this stage whether this refers to phase current or controller draw.
<<<<The S12S limits current only in PAS. They are realible enough if left alone. I don't think you can improve on the basic platform and when used with the Q100, none is needed. Actually, one mod is very kwel. one member installed the S12S internals in and earlier case that is much smaller. The size of the S12S is it's problem. >>>>
I also plan to investigate the use of oil cooling with ATF, these motors seems to respond quite well to it.
<<<I have used various Q100 models for several years at up to 15S Voltage in enviourments much hotter than that you will see, and contrary to what some will say, these motors are not prone to over-heating. I experimented with oil-cooling with the Q100 two years ago and it was a total fail. There is no way to install a external(to the bearing)oil seal and even with a double sealed bearing, it rapidly puked the oil out. That was ok on the chain side, but rendered the rear disc useless. Had to take the motor apart to clean the oil out. These motor are mechanicaly limited, not thermo. limited. Starting at 13S and/or currents above 20 Amps, they start to shutter and growl as the gears are being strained beyond their limits. The weakest link on these kits are the crimp-on phase wire bullet connectors. They are best replaced or elimitnated by soldering the wires.>>>

Still haven't heard from anyone if this part (https://bmsbattery.com/ebike-kit/705-dual-hall-sensor-12-signals-easy-assembling-pas-ebike-kit.html), the 12-count PAS sensor, is known to be compatible with the S-series controllers?

Many thanks, build looking good!

https://i.imgur.com/qy4p4WJ.png



IMO, these inexpensive kits are best left alone and enjoyed for what they are. But I don't have the skills and expertise for advanced projects. But it seems to me, that those types on advance skills would be better used on custom projects
 
https://i.imgur.com/rnHtPdJ.jpg

Why yes, that is a large pile of heavy gauge teflon-insulated Litz wire, and enameled copper...



"I believe your orginal rim is not suitable for ebike usage" <- what does this mean, not strong enough?
 
You can probably use your present rim if it has 36 spoke holes. Wheelbuilding is not difficult, and it's a useful skill to have. There's loads of Youtube videos on how to do it, or use Sheldon Brown's guide.

That PAS should be compatible, but for the sake of a few dollars, it might be worth getting one of the conventional type too - just in case.

Nobody has yet confirmed that the current limiting in the controller works. Hopefully, you can enlighten us.
 
Progress. The battery pack arrived, rest of the bits to follow tomorrow.

https://i.imgur.com/Qs1l9zt.jpg

A few problems with shipping, namely, being given the wrong tracking number, getting stuck in customs with no way of knowing what shipment is mine, and the seller being away for Chinese new year.

The pack looks pretty good, although I had to add some padding tape to stiffen up the connection between the mounting plate and the end-cap. Mounted on the existing lugs for the bottle holder. Mounting the controller will be more interesting.
 
It lives!

https://www.youtube.com/watch?v=JPTd81sTnKY

Not a particularly tidy installation, plenty of electrical tape and zip ties, but it's quite functional.

https://imgur.com/a/R3l3h

I decided to replace the DC bullet connectors with some locking MC4 PV connectors. I would like to do something similar for the motor phase connectors, as I don't require anywhere near the 1m of (rather inadequate looking) cable that it came with.

Before covering the hall sensor connectors with electrical tape, I individually insulated the contacts.

I'm unsure about the installation in the dropouts. The wheel ended up slightly tilted, and it looks like I could have got more of the locking nut to fit inside the dropout. The wheel is also somewhat out of true. Perhaps I would have been better off building my own wheel.

The thumb throttle is installed on the outside of the grip. I can operate it with the edge of my hand. No room for it with the bulky combo brake/shifter. Putting it on top of the shifter might work. The controller is held quite securely by the zip ties.

The performance is unexpectedly good! Hauls all the way to (indicated) 38km/h without any pedal input, I haven't yet explored what the combination of human and bike power can achieve. The motor was only a little warm after this kind of riding, and the controller was cold. I had set what I thought was a 25A/1.25 current limit according to the parameters, but that may be operating on the $CONTROLLER_MAX-0.5*n schedule instead. Pulls over 1150W. I will have to watch the torque on the nylon gears more than anything, I would love to see what it could do with some steel gears.

Even with an external speed sensor, it isn't currently reading the speed when freewheeling. I also had to guess at the motor pole count, which is set to 12.6 * 16 poles = 208 (no spec I could find anywhere), does anyone here know?

Haven't tried the PAS yet, it may yet make the throttle redundant.
 
It looks pretty good apart from the upside down battery. Is there a reason you did it like that?

There's a parameter that you can set to change the source of the speed sensor. I can't remember which one it is, but you can find it in the manual.

Do I understand correctly that you have a Q100H running at 25A?
 
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