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Niner Jet 9 Variable Control On-Demand Electric Assist

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    Received an nice piece of BLING from China today. It's a stem cap that closely matches the suspension bolts on this Niner Jet 9. Of coarse it has a small defect in it, but for 99 cents I say what the heck!

    The 12T MY1018 freewheel from China I received was defective. Luckily the seller says he will stand behind his eBay product and send out another one. I asked him to test it for correct operation before sending. Waiting on that now...

    After that arrives, the battery is the only thing left to buy before powering up.


      The replacement MY1018 freewheel has arrived. This one seems to freewheel just fine. I installed it and spaced the ISIS downhill bottom bracket with freewheeling sprockets to match the 12T/42T electric drive sprockets and the 30T/20T pedal sprockets

      Ended up scrapping the idea for a bracket that would hold the motor in place from rotating, because I came up with a wonderful simple solution. The 2013 Niner Jet 9 has two water bottle insert mounts on the lower down tube. I screwed the top mounting screw all the way in and rotated the motor up until it contacted that screw head, then I used a longer screw in the bottom insert with a locking jam nut. The bottom screw is simply backed out and tightened up against the motor, then the locknut is jammed adjust the frame insert. Super clean and simple. It isn't moving anywhere!

      Everything worked great on the initial pedal test ride. The motor freewheel simply spins freely with a faint clicking while I pedal. Only item left to purchase is the battery. Getting excited about powering up this new ride now!!!
      Last edited by Rider; 4 weeks ago.


        Still having a hard time finding the battery pack I’d like for this ride. Is there anyone in the SoCal area that can make a small light weight 36V battery pack with about 8-10Ah out of Panasonic-Sanyo GA batteries? My controller is limited to 25A and I want the pack to have a built in BMS. Preferred size is <3” wide X ~4” high X length pretty much open up to 12”. I know little about electronics or building my own battery pack.


          I decided to go with this battery:

          36V 16Ah/576Wh 10S5P with BMS made up of Samsung 3200mAh Li-Ion 18650 Cells; complete with 10S 3A 42V charger.

          It arrived quickly and weighs in at only 5lbs. 14-7/8oz. Measurements are: ~7-1/2" x ~3-3/4" x ~3-1/4"
          Last edited by Rider; 1 week ago.


            Now it's time to wire it all up...

            Most of the connections are straight forward, but a few clarifications are needed. The picture below is a page from the YIYUN YK31C 36V/500W (version) Controller Manual and pictures of the controller itself with the throttle I'm using. I used color pencils that match the wire color connections up the way I believe they should be connected.


            1) At the bottom of the manual page it states, "Fuse or circuit breaker protection is required between speed controller and battery pack." I assume that means between the first connection at the top of the page they call "Power Connector" or does the BMS take care of this?

            2) What does "VCC" mean in the "Ignition Switch" description? (Voltage Continuous Current? Just a wild guess.)

            3) The one connection I'm not sure of is the "Power Positive" GREEN wire coming off the throttle. I believe it needs to be a direct battery positive feed to give a correct reading for battery volt level. Is the "Indicator" RED positive such a feed? (I can and will check it with a volt meter once I hook up everything else, but it would be nice to know now if possible)

            The instructions says to connect everything "before" connecting the battery. My plan was to connect the battery and check each connection to juice levels first. I would hate to connect everything like it says, then connect the battery and find out the hard way I have something wrong. Although it is hard to make a mistake with such simple wiring.

            Any thoughts or suggestions are greatly appreciated.
            Last edited by Rider; 1 week ago.


              IT'S ALIVE!

              Pulled out a volt meter and checked the battery charge as received; it read 38.5V.

              Next I connected all the wires as indicated above except the GREEN throttle to RED Indicator Controller wire and both motor wires. The volt meter read zero for each of those. Pushed the IGN on button at the throttle body and the RED Indicator Controller wire turned full hot at 38.5V (BINGO!). Also checked the controller to motor RED wire and got 0V until I depressed the throttle lever; then up the voltage reading went (BINGO!). All appeared good, so I connected the rest of the wires, lifted the rear tire and hit the throttle. WE HAVE LIFTOFF!!! Of course an initial test ride was in order...

              VCC turned out to mean: Voltage Common Collector

              I went with the assumption that the BMS has a circuit breaker if problems arise and didn't put a manual fuse block between the battery to controller wires. If anyone knows this not to be true, please chime in. I'd hate to have the word ASSUME come back to haunt me as an acronym.

              I put rubber caps on all connectors not in use, including the charging plug coming off the battery.

              First impressions:

              1) As known the motor does make a noise similar to what I have heard many RC remote control cars make. It is not slient like a BBS02-B, but isn't intolerable for my intended purpose which is as an on-demand hill climb assist.

              2) For some reason I thought the throttle body and ignition on/off switch had three power level settings. Not sure why I had this in my mind (probably the 3 battery lever indicators on the throttle body), but it only has on/off. Not an issue when using a throttle as a variable power control lever though.

              3) I can hit 20mph in 5th gear. I can also hit 20mph in 3rd (1:1 on my S-A 5spd IGH) when not pedaling. The gearing setup was designed to be the 20mph speed limiter and it appears to be just about right.

              4) The throttle lever seems to stick in the on position at times, but a simple flick of the thumb sends it back to off. I think this is something simple to resolve and it might even stop after repeated use. Currently this issue is sporadic.

              I put the battery on the charger and hope to ride it over to my local mild MTB "loop" for a test ride climbing hills today. I will report back after a full test.
              Last edited by Rider; 1 week ago.


                First real test ride was a success! Did about 25 miles, of which about 10 was the Fullerton Loop; a mild MTB dirt trail with a few climbs. The assist let me climb hills I couldn't have without it with my current 30T X 20T sprockets. I'd really like to find a Sturmey-Archer C50 26T rear IGH cog for this eMTB. The Sturmey-Archer site says they make one, but I can't find one anywhere in the whole world. Lower gearing is the only real thing I came back from that ride with climbs wanting. Plenty of power if the gearing is better suited for the terrain.

                Because it is throttle only, I did find myself wanting to put it in 5th gear and ride to and from the trailhead without pedaling. That is hard to resist when it is available. I don't even have a throttle on my other eMTB that is now setup for road use, but it has 750W's of power at the push of the electric power level button which varies from 1 of 9 to 9 of 9 and it automatically bumps up the power until the speed of each level is met when needed.

                Successful, fun and great to be back on the dirt trails again is my first impressions. It didn't even have a full charge when I left and two of the three lights were still on when I finished. Next ride I will fully charge the battery and take a starting voltage and ending voltage reading for a better feel of power usage (no display). One thumb up and one thumb on the throttle so far!
                Last edited by Rider; 3 days ago.