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12V and 5v(USB) battery pack build. help.

Discussion in 'Power Electronics' started by Pexy, Jun 13, 2019.

  1. Pexy

    Pexy

    139
    3
    Feb 21, 2016
    Greetings!
    My brother asked me if I could build him a battery pack with 18650 cells that he got from work.
    He wants a 12V output and a 5V usb output. There are 8 cells in total.
    I was thinking of doing something in these lines:
    1) Connect 2 batteries in parallel and then 4 pairs in series.
    2) Get a 4S BMS for charging.
    -something like this: https://www.ebay.com/itm/3-4S-BMS-P...7QbTzAPwEeS2zlA6ZarHvIYWIaxgtcFvGB5SzJxzp1l4c
    or this: https://www.ebay.com/itm/3S-4S-5S-3...818b:m:mU0FwbeSu6Qs1LoApTvfXxA&frcectupt=true
    3) Use a 12V and a 5V regulators on the output of the BMS to have a regulated 12V and 5V USB outputs.
    - something like this for the 5V:
    https://www.ebay.com/itm/4-USB-Buck...m=333205758397&_trksid=p2047675.c100005.m1851
    - something like one of these for 12V:
    https://www.ebay.com/itm/XL4016-DC-...7a50:m:mKFxXwzaQeLUQA8Maz0fJpQ&frcectupt=true

    Am I going in the right direction and would something like this work?
    Do you have any recomendations. What would you change and why?
    All suggestions are welcome.

    Thanks,
    Sven
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,367
    1,903
    Nov 17, 2011
    Sounds reasonable.
     
    Pexy likes this.
  3. Audioguru

    Audioguru

    2,615
    591
    Sep 24, 2016
    The very cheap No-Name-Brand Lithium battery charger and protection board from China is listed at 40A!
    Does it work? Will it cause an explosion and fire?
     
  4. Pexy

    Pexy

    139
    3
    Feb 21, 2016
    Yes i don't trust it to handle 40A but I do trust it to handle around 5Amax that will be some what limited by the output regulator.
     
  5. Audioguru

    Audioguru

    2,615
    591
    Sep 24, 2016
    A protection board is supposed to protect against high load current. This one doesn't.
    What about the extremely high charging current? A mother disaster.
    Why doesn't ebay say the manufacturer's name?
    A car is also dangerous. Would you buy a cheap Chinese no-name-brand car??
     
  6. Pexy

    Pexy

    139
    3
    Feb 21, 2016
    Ok can you then recomend me a different board?
    As for the charging I was thinking of using adjustable balanced rc toys battery charger (IMAX clone).
     
  7. Audioguru

    Audioguru

    2,615
    591
    Sep 24, 2016
    I buy Name-Brand American Li-PO battery chargers from my local hobby shop. They are made for radio-controlled models and do not cost too much.
     
    Pexy likes this.
  8. hevans1944

    hevans1944 Hop - AC8NS

    4,250
    2,001
    Jun 21, 2012
    Gee, are those available now here in the USA? Can I get one with an autopilot so I can snooze while it moovze? I would rather have a Kia Turbo Sport, but mebbe Chinee be all better, huh?
     
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