My eZuma project (Elektra)

Discussion in 'Electric Motorcycles' started by MJSfoto1956, Sep 16, 2018.

  1. EvrythingAwesom

    EvrythingAwesom Long timer

    Joined:
    Mar 30, 2016
    Oddometer:
    1,406
    Location:
    Bahamas
    IMHO, no BMS is a big mistake. Done that. $$$$ battery pack destroyed.

    Do your 18650's have hi/lo protection?
    #21
  2. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    I haven't made a decision on which battery type yet, much less finalize the choice of controller (although I am getting much closer). I should add that there is plenty of evidence that a failing BMS can destroy packs too, which gets to the heart of the matter. Which battery chemistry were you using when your was destroyed? And did you follow the specific methodology outlined in the linked video?

    Michael
    #22
    EvrythingAwesom likes this.
  3. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    I don't dispute the data @ Battery University. But that is precisely the point: charge your batteries to the max and it will shorten their life, that fact is well documented. It seems there is general agreement that 4.1v is the "sweet spot" with regard to LiPos. So I guess we can split the difference.

    M

    P.S. In fact, the cell phone industry did a study looking at the effect of LiPo fully charged voltages in relation to cycle life. These tests were done under ideal laboratory conditions and of course the 80% depth of discharge rule was obeyed! Here are the results:
    • Charge to 4.1V gave over 2000 cycles.
    • Charge to 4.2V gave about 500 cycles.
    • Charge to 4.3V gave under 100 cycles.
    • Charge to 4.4V gave less than 5 cycles.
    #23
    voltsxamps and Lesharoturbo like this.
  4. EvrythingAwesom

    EvrythingAwesom Long timer

    Joined:
    Mar 30, 2016
    Oddometer:
    1,406
    Location:
    Bahamas

    Your data is for LiPo. Not mine.
    #24
  5. EvrythingAwesom

    EvrythingAwesom Long timer

    Joined:
    Mar 30, 2016
    Oddometer:
    1,406
    Location:
    Bahamas

    My 'cycles were all LIFEPO4's.

    I have some detailed essays on Lithium somewhere in the scooter forum.
    #25
  6. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    FWIW, I'm leaning towards 21700s. With a single 20s8p bank I can get 40Ah which would provide 320% greater range than my current AGMs. And that would still leave room for a second 20s8p bank which would then bump my bike into 80Ah territory.
    #26
    EvrythingAwesom likes this.
  7. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    So when you work on Chinese bikes you need to be ready for anything. When someone says Chinese bikes are junk they are not necessarily talking rhetorically. Take their plastic -- please! I have two Chinese scooters (one ICE, one electric) and a common issue is brittle plastic. While the panels are faithful to their Yamaha Zuma/BWS originals, the plastic used is not as flexible. That leads inevitably to broken alignment tab/pins. Rather than be dismayed, the determined wrencher finds work-arounds. Such as it was with my broken alignment pins. My fix is as follows:

    STEP 1: use cyanoacrylate (a.k.a. superglue) to reposition the broken tab/pin in its original alignment. Note: this will NOT be strong enough to fix the break, We simply need the pin to remain in position as we perform the remaining steps
    STEP 2: grind down the top of the pin flat with a Dremel
    STEP 3: drill out the pin all the way through its support structure
    STEP 4: drive a stainless steel screw all the way through leaving 10mm or more exposed under the support
    STEP 5: mix up a batch of plastic bonder epoxy and spread that goodness all over, letting it build up in the corners and crevices. Likely need to do several applications.
    STEP 6: let it cure then sand/grind any roughness smooth as needed
    STEP 7: re-install the panels and get back to work on your other tasks.

    Below are some pix of the final result which is "strong like ox".

    IMG_6424.jpg

    IMG_6425.jpg
    #27
    voltsxamps likes this.
  8. EvrythingAwesom

    EvrythingAwesom Long timer

    Joined:
    Mar 30, 2016
    Oddometer:
    1,406
    Location:
    Bahamas

    Does that require a rear shock absorber upgrade, or not?

    My eGrom's LiFEPO4 pack was only 26AH.
    #28
  9. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    Shouldn't. A 40Ah LiIon pack should weigh about 75% of my current AGM batteries! :p

    M
    #29
  10. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    #30
  11. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    Making progress on the design and layout of my battery pack. This is one of the concepts I am considering which just barely fits inside my existing battery box! Such a pack would deliver approximately 3.2x the range of my current 20Ah AGM battery pack. I'm hoping for 75 mile range with this, maybe a bit more. This design requires 320 18650 cells.

    NESE Modules 20p pack.v3b.1440.jpg
    #31
  12. ctromley

    ctromley Long timer

    Joined:
    Oct 18, 2012
    Oddometer:
    1,089
    Location:
    PA
    Looks OK in general. The little PCBs are presumably bypass regulators to prevent over-volting a module perhaps?

    One thing I don't see, either in your setup or the UConn approach (which I just scanned lightly, didn't get into it deeply), is fusing for individual cells. The chances of a cell failing short are small, but it does happen. When it does, all the other cells (15 in this case) simultaneously dump all the current they can through that shorted cell, which lights it on fire, which spreads to the other cells and eventually to the whole pack. Your vehicle and all your work will literally go up in flames.

    The way you prevent that is by having a common + or - bus for the cells in a parallel module, and each cell connects to the bus through a fusible wire. (This is what Tesla does.) It's not a hard concept or difficult to implement, but no one in the scooter/ebike space seems to do it. Now you have some tidy little 8-pack modules there - if you open the case do you see what I'm describing, or just all the cells spot welded directly to common electrodes? Or maybe all cells joined to nickel strips that might act as fusible links? If the latter, what are the specs of the nickel strip (I hope it's pure nickel, or it won't age well) so you can determine its ampacity and thereby know if you're getting decent fail-short protection?
    #32
  13. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    Somewhat. Described in better detail here:



    The UConn team uses a very cool module from Lithuania with internal fusible links as you describe, a rather robust, albeit expensive, design if I might say so (see: https://www.energusps.com/shop/prod...with-temp-sensor-3-6v-20ah-18c-325?category=3). The solderless modules I am considering (ironically also from Lithuania) in this sketch do not, but as you guessed have tin-plated copper strip connecting two blocs of 8 cells in parallel. I am considering fusing these 16p packs between their serial neighbor, but that might be overkill with the BabyBloc modules. TBD.
    #33
  14. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    This is a rough sketch of what the top end of a 40Ah 3.6V 16p pack would look like using a combination of two N.E.S.E. modules in parallel + one BabyBloc balancer.

    NESE + BabyBloc combo.1200.jpg
    #34
  15. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    I need some advice. My Chinese CNC swingarm has provision to attach the rear shocks at various points as shown in the photo below. So far so good. However, the ID of the mounting holes are an odd-to-me 8.9mm (0.035"). And therein lies the problem. My shock's clevis mount uses M8 threads (8mm). That leaves 0.9mm for the shock to rattle around, which over time would destroy the swingarm mounting point. I ordered some 10mm "shoulder" bolts which are grade 12.9 and are designed just for this kind of thing. Should I ream out the 8.9mm holes to 10mm? Should I turn the 10mm shoulder bolt down to 8.9mm? Or should I try something else?

    M

    IMG_6439 (1).1280.jpg
    #35
  16. webmonstro

    webmonstro A Aventura Continua....

    Joined:
    Jul 21, 2008
    Oddometer:
    1,134
    Location:
    Portugal
    I would open the holes to 10 mm . The bolt will remain stronger and if you ever need a replacement bolt you can just get one off the self

    Nuno
    #36
    Hannda and firstshadow like this.
  17. voltsxamps

    voltsxamps Advolturer

    Joined:
    Mar 20, 2016
    Oddometer:
    1,707
    Location:
    +positively grounded-
    Are you able to find a bushing .9 mil in thickness to eliminate the play?
    #37
  18. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    I would love to find a 0.45mm wall thickness bushing (man that would be thin!) -- that would be the easiest solution by far. AFAIK, such things only exist in China for those "in the know".

    M
    #38
  19. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    here's an alternate battery design using 20700's in a waterproof junction box, which would allow me to swap battery packs. 72V @ 42.4Ah. This design requires 200 20700 cells.

    320x240x110 junction box aliexpress3.1280.jpg
    #39
    voltsxamps likes this.
  20. MJSfoto1956

    MJSfoto1956 Been here awhile

    Joined:
    May 12, 2017
    Oddometer:
    488
    Location:
    Boston, MA
    I might add, there is room for one more 1s10p module, split in the empty middle section. That would make for a 21s10p pack delivering 75.6V @ 42.5Ah.
    #40