Moped Li-Ion charger

Discussion in 'The Projects Forum' started by 570rm47, Aug 21, 2013.

  1. 570rm47

    Thread Starter New Member

    Aug 21, 2013
    This is part of another project my "Methanol Moped". Its going lots slower than i thought it would, still heaps of motivation and enthusiasm though. I want some power, for lights is a good start 60km/h and you cant see the pothole in the dark is freaky. I would like to use polymer Li-Ion battery's recycled from a cell phone i had 5 identical 3 left.
    My moped is 46cc retrofit kit for a bicycle, has the same engine as mine but has a newer revision the differnce being 21mm stroke distance and mine is 26mm. The magneto coil is still the same.
    I got started in the right direction with some foggy memories from school, thrashing google and an email to motrax i was Given this about the electrics.
    "A single diode will not be suitable. You will need three diodes to form a Weignbridge rectifier.
    The current draw should not exceed about 0.7 a or it will kill the engine."
    Any comments on this it confused me so i thrashed google some more and still am unable to find out what a Weignbridge rectifier is, i think a diode bridge aka bridge rectifier is still the solution so far.
    I got out the multimeter and tested the voltages coming out of the wire on the coil that is not used to fire the spark plug, this coil also doubles as the kill switch for the engine and get 5.6v at its lowest idle and 7.85v when im going as fast as i like to.
    Next was a trip to the local rewind professional he wouldn't help but offered to charge what seemed really unreasonable and way beyond my means for him to do it, fortunately an employee overheard and was persuaded to part with a bit of advice provided that some properly preped ethanol was forthcoming. He gave me a KBPC608 Bridge Rectifier which i then wired to a SLA 6v 7.2ah and 2 really cheap 5 LED torches that normally take 4 aaa's each. It seemed to work ok, forgot to turn the lights on daytime and it was bad.
    Tried to replace it with parallel pair of li-ion batterys 3.7 V 1100mAh 4.2 volt charge limit, more heat and Smoke.
    So i guess that i need to add a capacitor and then a zener diode another capacitor and a diode and then um well a li-ion charger wish i could steal the bits from the phones that i still have there screens are broken.
    Any ideas, I love links =) with a handful of design considerations that are a little out my usual auto electrical and electronic experiments( ) it is little more complicated than i suspected.
    I am unsure if it is appropriate but i will mention a couple of other threads i am starting and add links later, Moped Magneto coil rewind Magnet replace, Moped CDI.
  2. 570rm47

    Thread Starter New Member

    Aug 21, 2013
    Please forgive me terrible grammar it wouldnt all fit
  3. wayneh


    Sep 9, 2010
    This topic might fall under the automotive modifications ban here. We'll see when a mod comes along.

    In the meanwhile, it's very hard to follow what you need help with. Do you have some specific questions? Try to organize the details so that your grandmother could understand. Then maybe we'll be able to contribute.