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Battery project

  1. Aug 22, 2015 #1
    so i want to make a ebike battery out of 18650 cells, i've done all the research about series and parallel and balance charging but what is still unknown to me is i know i want 36v coming out of the battery and i don't know how to find the amps that the battery is capable of putting out, is the amps based off of the battery or how much the electronics it is wired to PULL from it. (so does the amps depend on the battery or how many amps the electronic, my motor 500w 36v, needs.
     
  2. jcsd
  3. Aug 22, 2015 #2

    Bystander

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    Specs. on "18650" read 2-3 A max. discharge.
     
  4. Aug 22, 2015 #3

    meBigGuy

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    The amperage the batteries are CAPABLE of supplying at the output voltage is one specification. The load may or may not CONSUME all that current capability at the operating voltage.

    So, if the batteries are CAPABLE of supplying 10amps at 36Volts, and the load only CONSUMES 8 amps at 36V, then the batteries will simply provide the 8amps that the load consumes. But, if the load needs 15A at 36V, then the batteries are under-rated for the load and something needs to give.

    The Ampere-Hour rating of a battery is specified/measured at a specific load current. Drawing more current than that load will result in an actual lower Ah capacity (not just a shorter battery life)

    For example, a 2400mAh 18650 is rated at 240ma. It will lose half its capacity if you discharge at 4A. It becomes a 1200mAh battery. That is in addition to the fact that it discharges faster because you are drawing higher amperage. Again, this is a actual reduction in Ah capacity,

    Here is a curve from http://www.candlepowerforums.com/vb/showthread.php?84980-2400mAh-LG-18650-cell-discharge-graph

    18650_2400mAh.jpg
     
  5. Aug 22, 2015 #4
    so if i get 40 18650 cells in 4 paralleled and 10 serial how many amps is that capable of pushing out.
     
  6. Aug 22, 2015 #5
    and also a lot of people have a balance charging circuit board of some sort. where can i get one. and how do i wire it for my 36v, 4 paralleled, 10 serial 18640 cell battery pack
     
  7. Aug 22, 2015 #6
    keep in mind i have a 500w esc and motor 36v
     
  8. Aug 22, 2015 #7

    berkeman

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    Wow. It is just too dangerous for us to encourage you to do this project with so little education in electronics. Best case you end up with a system that doesn't work very well. Worst case you start a fire that hurts you or somebody else. (Do not ask me how I know about fires in battery powered systems...)

    This thread is closed. Please take a basic electronics class (in person or online), and learn the basics so you don't need to rely on Internet advice that you don't understand. Please be safe and smart.
     
    Last edited: Aug 22, 2015
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