My Jeep Comanche E-Bike

[Russell]

This is my third ebike build and like the previous two follows the same basic formula; a 700C/29er frame with a small geared front motor. My first bike (viewtopic.php?f=6&t=8579) simply rode too stiffly on rough rodes and trails, the second (viewtopic.php?f=4&t=10458) with its steel frame and big tires was my favorite and I rode for it thousands of miles. Still with the straight, stiff fork I needed to keep the front tire pressure quite low (<30 psi) to get any real “suspension” from it. I also wanted disc brakes which leads me to this third build.

I picked up a new Jeep Comanche 29er mountain bike on eBay for about half of list price ($150 delivered). It has an inexpensive Zoom suspension fork with STEEL lowers making it perfect for a front motor. The fork has no adjustments whatsoever and limited 65mm travel but for the road and for what I want it does the trick. Here’s a pic from the Manufacturer’s (Kent) site;

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After transferring a number of parts (wheels,crank,fenders,brake levers,shifter) from my now decommissioned Raleigh ebike and the Topeak bag and controller from the Kona Smoke I sold the bike looks like this;

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I really like the way the bike turned out especially considering the low investment. On the road the bike rides smoothly with the front suspension providing just enough give when hitting ramped curbs and pot-holes.

-R

[thewmatusmoloki]

Nice clean looking ride Russell. I like.

[Russell]

Thanks.

It's the cheapest bike I've ever bought and the paint job leaves a lot to be desired but the frame is well made. I ride a large frame and did have to swap out the seat post for a 400mm one but otherwise it fits me well. It was easy to upgrade with my used parts and now it's more a "hybrid" bike for the road than a mountain "29'er" but that suits the riding I do. A long 114cm wheelbase helps make it stable and the short travel front suspension fork takes the hard hits which my arms used to have to absorb on previous rigid fork bikes. Overall it does make a good basis for an inexpensive ebike conversion.

-R

[motomech]

Russell,
25 questions
You were last using the Ebike kit mini-motor[best left un-named, I guess], why did you go back to the GM?
Is that GM the one you rebuilt using parts from a Bafang?
Did you try mounting the motor with the stock disc? Clearance issues?
Are you are still using the Ecrazyman controller[can't tell from pic., it looks a little large], is it un-modified, something around 17 Amps?
Still using 12S of Lipo.?
That triangle space sure looks inviting, is it because your pack is small that you resist going there?
Thanks

Gary

[Russell]

Motomech,

I used the E-BikeKit mini-motor for several thousand miles and it performed very well. Speed was just right with the 51.2V LiFePO4 battery I had but that battery died. I sold the motor/wheel for a number of reasons but mainly because I was converting the Kona Smoke bike on which it was being used back to original condition for resale. The plan was to use just my Raleigh ebike with the Bafang but the bike was too punishing on the roads around here so I scrapped it and moved the parts to the Jeep.

The motor on this bike was purchased from Golden Motor but it is a Bafang so that's what I often call it. The first Mini Motor they sent me had a damaged case so they sent me another complete motor. That's another reason I'm using the Mini, because I have a spare motor core I could drop in if this one is damaged.

I tried the stock 160mm rotor but the caliper hit the outward bound spokes (heads facing in). I had to go all the way up to 203mm to clear the spokes. If I had built the wheel with all of the heads facing out it probably would have cleared.

I'm not presently using the Ecrazyman sensorless controller. It works quite well with the geared motor but not as good as the Universal 9-FET controller (in sensored mode) from BMS Battery you see attached to the seatpost. This is a nice controller that doesn't get much press here. It can operate in sensorless mode to help get me home should a hall sensor go out, it has cruise (which I don't use), and it has a DYNAMIC LVC circuit, not a fixed LVC voltage, which adjusts to the battery being used (more on this below).

Yeah my only battery as of now is a pair of 6S 5000MAh Zippys. Because I don't have any cell level protection on the pack I rely on the LVC of the controller to keep the overall pack voltage from going too low. This is when the dynamic LVC circuit of the BMS Battery controller comes in handy. I haven't seen any documentation on it but it appears to sense an unusual delta V as a weak battery at which time it cuts power. I ran the battery to the limit yesterday and today and it does work to keep the pack from dropping too low for its own good.

I'm still trying to decide on a larger battery to buy. When I do buy it though it will go into the rear trunk bag. I pedal a lot and need water so I don't want to loose the WB cage

-R

[motomech]

Russell,

Ah yes, I remember the motor with the damaged housing now. It was decent of GM to send you another. Frankly, with the procession of motors you have used, it's a little difficult to keep track. A bit like the peanut in the shell game

The Hightecbike kit[MXUS]that I have came with all the spokes as "inners", but still, the spoke heads just clipped the stock[placement]caliper. I spent more time carefully grinding clearance on the caliper than I did with the wheel fitment.

Interesting about the LVC feature of the BMS Battery 9-FET controller, I had no idea. I will be using my C.A. for LVC, so I will probably stick with my stock Shenzhen controller. I have a Holmes Hobbies Mini-Stealth controller[23A actual] as a spare that I might try out sometime. Perhaps with the C.A. current limiter.

Concerning a larger pack, why wouldn't you add more bricks to your two Zippy's?
I'm in the process of putting together a Lipo pack at the moment. Like you when you did yours, I'm doing a bit of soul searching as to which configuration, 12S, 13S[I also have a spare 48V Li-on charger not being used] or 14S. And like you, I'm going to go with 12S for simplicity's sake. The Turnigy 6S 5000 mAh [20C] from the USA warehouse for $42.63 ea. seem to be the best overall deal at the moment and 22 to 23 m.p.h. is fast enough for me.
Now the charger decisions

At any rate, I would like to take this opportunity to thank you for your reviews. I've read every one, at least twice[even with the messed-up text]. Your voice of sanity and ability to resist the upward power spiral has brought me back to Earth more than once.

BTW, poor paint job not withstanding, the burnt orange color w/ the black accents look great.

Gary

[Russell]

I haven't done all that much wih this bike except ride it (1,167 miles as of today). I know folks on this board love their high-powered e-bikes but I will say again that a small 250W geared motor is the perfect motor for a human-electric powered hybrid bicycle. I built a more powerful e-bike which I can ride like a scooter if I wish but for cycling fun I always choose this Jeep/Bafang bike because it is more like riding a conventional bike...only faster.

What makes this bike more fun is the little high-speed Bafang motor which on a freshly charged 12S LiPo pack will accelerate me up to 29 mph with the low to mid 30's easy to reach on any down grade (somewhat limited by leg speed w/42-12 gears). Yes, being a higher speed motor in a 700C rim it definitely lacks low speed grunt so I do need to keep it above 14 mph under load lest it (audibly) protest, but that's where the human power comes into play. With enough gears in back (...yes I use them) I can keep the motor in its' happy place and get plenty of exercise doing it.

One thing I have done is upgrade the battery from 2x6S 5AH Zippys to 2x6S Turnigy 8AH NanoTech LiPos. http://endless-sphere.com/forums/viewtopic.php?f=14&t=40636&start=15#p600251 So far I am impressed with these batteries; internal resistance is quite low which translates into little voltage sag under load and they stay very well balanced. I probably wouldn’t need to balance them at all ‘cept I’m kind of anal about it so I do it every few charges anyway.

Another thing I have done is play with controllers. The controller I used initially was a BMSbattery “universal” 9-FET controller. I like this controller since it has an adaptive LVC that works on both 36V and 48V packs. It also works sensorless but not very well with a freewheeling geared motor. For fun I tried my Ecrazyman 6-FET 18A sensorless controller again but while it originally impressed me this time around on this motor it needed a light touch on the throttle on take-off or it would hammer. Also as I noted the first time I used it will hammer a bit if the throttle is pulled abruptly after coasting without power for a while. The controller I’m running now is a 48V KU93 9-FET (also from BMSbattery). I enjoy using the (8-sec) auto cruise feature and the LVC provides some level of protection for my LiPo pack. Initially when I switched to this controller I cut one of the shunts to run at 15 amps but the motor felt very lethargic. I've run small slow-wind geared motors at 48V/15A with good results however this faster wound motor does seem to need more current to get it going. Also since I was into the throttle for a longer period of time at 15A I saw no difference in power consumption so I tweaked the controller back to 20A. Today I tried this controller sensorless and was truly impressed. The only price for this performance is a slight but noticeable lag between applying the throttle and response from the motor. I also got it to “burp” once under load up a hill when I let go then reapplied the throttle…but that was it. It is difficult to tell this controller is running sensorless, it’s that good!

This brings me to the reason I ran the controller in sensorless mode today. In search of some FREE power I replaced 6 ft of the stock puny motor wiring with 3.5 ft of 12AWG cable.

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I wanted to get out and test the mod and the controller in sensorless mode so I didn't make up a hall sensor cable. The cable swap is a small change but I could instantly detect something was different the first time I pulled the throttle. The geared motor runs pretty quiet however at low speed/high load conditions it does generate some noise and today after the mod it was significantly louder and it did feel stronger and seemed to pull better up hills. After a few rides I'll try it sensored again to see if there is a difference. In the future I'd like to get my hands on a controller with IRFB3077 FETs to see how much of a difference the low RDSon resistance of those devices makes in the real world.

-R

[Russell]

I finally broke 50 MPH

Yeah it was downhill and only for an instant at the very bottom but it stands as the record speed on any of my e-bikes.

top speed down a 13% hill

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Getting up the hill with the little (high-speed 9.1 RPM/V) 250W Bafang on 12S LiPo at 20A was another thing. The hill in question is the steepest I know of in the area rising at a steady 13% for 1,000 feet. I tried it with my other e-bike sporting a (8.3 RPM/V) Bafang BPM, first at 20A then at 27A, (both on 12S LiPo) and crested the hill at 10 and 14 MPH respectively while pedaling vigorously. It was with some trepidation that I approached what looks like a wall rising in front of me spinning fast in the seldom used 30T front chainring at about 20 MPH. That speed dropped quickly and at 10 MPH the motor was below its' happy place and loudly protesting. I thought about turning back but instead downshifted to the lowest gear combo (30T/30T) and pedaled with part-throttle at 7 MPH to the top of the hill. I turned around, flew down the hill and completed the remainder of the 34 mile ride.

-R