kingb said:
Turbo - Thanks for the detailed response.
I am beginning to reconsider a bit - I definitely want distance over speed, and the main purpose of having a motor on my touring bike is to get up hills without killing myself.
What is the max speed of your 12v bike, and how does it do on hills?
Something like that sounds ideal to me, as long as it can get me up long stretches of highway slope (such as on the HWY 1 in oregon and northern california) with pedal assistance like I was on the flats. I could definitely see getting a low voltage motor and 4,6, or even 8 of those linked batteries. And for when I feel like just cruising I could coast along under 20mph with the motor
kingb said:
I would really like to hear about your 12V custom build, sounds like the way to go for maximum Ah. Plus I am trying to figure out a solar setup (my other thread), 12v would work nicely with some panels ive been looking at.
Sorry it took me so long to get back with you but the last few days have been hell on earth and I haven’t had almost any spare time whatesoever. Finally got a slice of free time so I’m replying to you now. Better late then never.
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Before I get into some of the details on my 12V system build, I first off would like to point out that almost all of my builds regardless of voltage level with few exceptions are designed specifically to closely match the human and electric motor power together in a true symbiotic relationship where human power output and electric motor output closely match each other. In some of my lower power builds (100-300 watts mechanical output power) the electric motors output is less then peak human power output when the rider (me) is standing up on the pedals and really “jamming it” for maximum human pedal effort output but is about the same or more than normal sustained human pedal power output. In other cases the electric motors power output is about the same or slightly more than maximum effort human power output and is thus substantially more then normal sustained human power output.
At least for me personally, 500-watts or so is about what my peak maximum human power output is and 150-200 watts is what I can sustain for 1-2 hours and if I’m on long distance trip 100-watts or so is the effort level at which I can personally pedal all day long at. My personal maximum effort “stand up on the pedals and jam it” power output occurs in the 60-70 RPM pedal cadence range and my most comforrable pedal cadence range for sustained normal human output over distance is in the 90-100 RPM pedal cadence range.
Thus with my builds to accomplish my primary goal of matching the electric and human motors together in a true symbiotic relationship I select a gearing ratio between the motor and the pedal cranks such that when the motor is at its peak power output “sweet spot” in its curve at full throttle the matching pedal cadence is at or just over 60 RPM so both the human motor (me) and the electric motor both produce their peak output together. Then at slightly higher electric motor RPM when the electric motor is producing less then maximum power output but is opperating at maximum or near maximum efficiency on the downhill side of its curve I want a matching pedal cadence that is in my normal sustained comfortable pedaling range of 90-100 RPM or so.
If you set-up an e-bike in that way and then run the combined power of both the electric and human motors through a normal bicycle gearing system you then can then effectively do everything that a normal pedal bike can do as far as gearing down to climb steep hills or gearing up on the flat to go faster. But you either don’t have to pedal or if you do pedal its like two (or more depending on the electric motors power level) people were pedaling not just one so you can climb hills a little faster not having to gear down quite as much and go a little faster on the flat being able to run steeper higher gear ratios.
It’s like riding a tandom without your stoker not weighing quite as much as normal and possibly beign a really strong cyclist (think Lance all pumped up on artificial enhancements if you are using a 500+ watt motor) and even better the stocker don’t talk back or complain and is a slave to your electric motor throttle switch.
That kind of gearing set-up between the human and electric motors power output combined with a motor of limited power (not much more then 250-watts peak output) is at least in my mind the most critical factor in making a long range set-up and is far more important then the voltage used. If a 12v system is set-up that way or a 144v system is set-up that way it makes little difference for the end result. Usually though a higher voltage system means a faster spinning motor and thus more reduction is needed to match it to the human power output. And if you are using a set size battery cell the higher the voltage the more sells you have to carry as a bare minimum to make the system work. If your carrying a huge battery of 2+Kw for long range capabilities it really doesn’t matter all that much, its when your just doing a short run that a lower voltage system can allow you to carry a smaller lighter weight battery without getting into rediculously small cell sizes.
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Okay, all that background information put forward, in specific answer to your questions
As far long range capability. The 12v build of mine you specifically asked about uses two 6354 RC motors that were custom modified by installing longer motor shafts and hall sensors. The longer motor shafts so the motors could be mounted in the bike frame by hanging them by their shaft ends between two parallel side plates with the longer shaft ends allowing for sprocket mounting and extra bearings on each end by which they are hung in the side plates. The hall sensor addition being necessary in order to run them on an e-bike controller (Kelly does make some that will work with a low voltage 12v system, they are the only ones I know of who do) to avoid having to use RC motor controllers and having to rig up a custom throttle assembly from a servo tester. Each of the two motors is capable of putting out slightly over 300-watts maximum power output and about 150-watts maximum efficiency output. That is watts out not watts in. So running just one of them (switch off the motor cotnroller on one of the two) I can run at high effeciently at low power by doing my part pedaling into the motor pushing it into its peak efficiency zone where it not only is more efficient but also consumes less power altogether. This allows for some pretty incredible long range capabilities for an e-bike as explained earlier.
When climbing hills I can switch on both motors at which point with them both in their peak power output range they together exceed what I am capable of even when putting out my own maximum effort. Which means that even without me pedaling they will climb any hill I could climb on a pedal only bike by gearing down and standing up on the pdals and pedaling as hard as posible at maximum effort and will do it just as fast if not faster and unlike the human motor they don’t tire out quickly doing that and can continue that pace for as long as the batteries last. Add into that the human also pedaling strong, maybe even at maximum effort while hill climbing and you can really climb some hills.
So far with that bike I have climbed the “Homestake Pass” just to the east of Butte, Montana several times riding the shoulder edge of I-90 (look it up on google earth) and although I can most assuredly tell you that I didn’t fly up the pass and it did slow me down I have had no trouble climbing it and it took me a heck of a lot less time and effort then the one time I biked over that pass on a pedal only bike. That isn’t the steepest hill I’ve climbed with it either, but it is the largest over all mountain pass I have climbed with it. Some of the small hills have been steaper but not near as long or as much over all elevation change.
As far as speed, on the flat with one electric motor running and doing my part on the pedals and pushing the motor into its maximum efficiency zone I average about 20-mph or so. That is when I’m running for maximum range. If I want to go for all out speed switch both motors on and pedal hard and I can push it above 25-mph but still under 30-mph but its incredible how much that extra 6-8 mph eats battery juice up and can cut down the range to a 1/3 or so of what is possible doing only 20-mph with only one motor switched on and keeping the pedal RPMs up strong and pushing the electric motor into its most efficient zone by taking on some of the load yourself.
Running both motors while geared down climbing a big hill doesn’t cut range down all that much because although you may use a little over twice the power per the same amount of time to climb the hill you climb it nearly twice as fast so its generally well worth it especially if you get easily annoyed climbing only at normal human power output speeds of just a little over 5-mph, constistently maintaining 10-mph or so while hill climbing “feels” much better and doesn’t get annoying making you feel like your crawling up the hills. But if you try to go fast at 25+mph on the flat instead of being content with about 20-mph with one motor combined with strong sustained human pedaling you start using up more then twice the battery power in the same amount of time for only a marginal increase in speed so it substantially reduces the over all range.
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As far as 12v low voltage builds in general:
They are rather difficult to accomplish and you have to pretty much build them almost completely DIY from the ground up. It’s a little easier if you use a brushed motor but their reliability and efficiency is often considerably less then brushless technology and they often weigh considerably more for the same power output compared to brushless.
If you want to go brush-less like I did on that build your basic two options are to either find a large brush-less car radiator fan off of a high end import Cars/SUVs which are sometimes equipped with fairly powerful brush-less three phase motors with hall sensors for their radiator cooling fan(s), we are talking junk yard diving to find a good one in running condition that can be modified to serve as a mid-drive motor.
Or use an RC motor repurpossed and modified to serve as a mid-drive motor.
I was unable to locate one of the car radiator burshless motors that I liked and most of them I would have had to extensivly modify more then I would with an RC motor so I went with the RC motor option on my one 12v brushless build so far (all of my other 12v builds have been with brushed motors).
12v brushless motor controller options you are pretty much limited to either RC motor controller (usually sensor-less) or Kelly does make a few e-bike type controllers that will work down to 12v (requires motor to have hall sensors).
You should realize that it took me over a year to build that bike sourcing the components and modifying them and making them all work together.
24volt system is about the lowest voltage your going to be able to find off the shelf reasonably available motors and motor controllers for without having to resort to modification and fabrication to get it to work. And you can certainly go higher then that and still get everything to work out. Voltage actually doesn't matter so much If you limit the amps enough on the controller and use enough reduction to gear the motor to closely match the human pedaling so that the human and electric motor work together in a symbiotic relationship and unless you are willing to really dig into it you probably shouldn't try to do a build at a lower voltage system then that especially for your first build.
Part of the reason for going lower voltage on many of my builds was so that when I don't have to go a long distance I don't have to pack the weight around of as many of those batteries I've mainly been using. 24v system means I only have to take two of them if I don't need the others for range, thats only 14 pounds of battery where as compared to a 48v system I have to take four of them for twice the battery weight at 28 pounds even if I'm just only going a couple miles. Obviously with a 12v system I only have to carry one of them that only 7-pounds if I’m not going far enough to need more then that in battery capacity.
The other part of the reason was for night time riding lights. 12VDC automobile lights are very bright, cheap, and plentiful especially with all the LED versions out nowdays along with all the stuff to make them work – switches, relays, flasher units, pulse flash at initiation and then solid on brake light controllers for improved safety (made for improved safety on motorcycles but work great for e-bikes as well).
Of course that doesn’t just apply to 12VDC systems although more expensive and not quite as plentiful of selection there are a lot of big rigs that use 24VDC electrical systems and a lot of LED lights and wiring components available for them as well.
Long story short, unless you are really into it and really want to put in a whole lot of effort to make a 12volt system work and it really is worth it for you a 24volt system may actually be a better choice. You can still get lights and such for that voltage level you just have to buy big rig 24V compatible LED lights which are more expensive with less selection then 12V automobile lighting systems but still more and better lights for less money then e-bike lighting systems designed to run on 36 and 48 volt systems and you can find e-bike motors and controllers for 24 volt systems and you aren’t completely out in custom DIY from the ground up really hard to find components “no mans land” like when you try to build a 12 volt system.
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If you really do want to put in the time and effort to build a 12V system. Alien power systems does sell a 80100 RC motor that has already been pre-modified with hall sensors so you don’t have to mess around with that annoyance of custom work to be done. I can’t guarentee that it will run good on only 12 volts since I haven’t actually tried it but it should be able to take more amps then the 6354 RC motors I’m running and thus quite possibly is capable of getting the same power levels I am using only with just one bigger motor instead of two smaller ones. Mated to the largest size highest amperage controller that Kelly offers in its low-voltage 12v-24v controller series it might just be the trick.
I am also planning on doing another 12 volt build using one of the motors LightningRods is using in his kits and also selling just the motors alone. It could be a while though before I get the motor from him and am able to put it in operation in a build. But again since I haven’t actually done it yet myself I can make no guarentees.
Only brushless motor set-up I know of that works for sure in a 12 volt low voltage system is those 6354 motors I picked up online and then modified. I’m sorry but I can’t remember exactly which site I bought them off of but they were 200-Kv motors with the larger shaft size (two shaft sizes available in that motor size the larger of which is the same shaft diameter that is used in the larger 6374 RC motors which is where I got the longer shafts which were replacement shafts for the larger 6374 motors) that were advertised as being suitable for running on 4-6 cell Li-Poly RC packs and a 4-cell Li-Poly RC pack is a 14.8 volt pack so not a huge stretch from their specs. to run those motors on 12 volt system.
Then of course you can always run a 12v brushed motor which aren’t too hard to find and you really don’t even have to have a controller with them and can use just a simple on/off switch with the lower powered ones without issues. Problem for a long range set-up with them is their efficiency and reliability are a whole lot lower then a modern brushless motor and thus in most cases you would probably be better off with a brushless 24v system then with one of them.
Good to know about the range estimates too. 
