1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Help with Reverse Engineering Li-Ion laptop battery BTY-M6D

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by P.Vlad, Feb 28, 2016.

  1. P.Vlad

    P.Vlad New Member

    Joined:
    Feb 28, 2016
    Messages:
    2
    Likes:
    0
    Hi guys,
    I'm quite the newb when it comes to electronic circuits therefore I need your help with this. (also after some pondering I figured this is the right thread to post instead of "repairs")

    Background: Laptop power jack is wrecked went to the repair shop, they tried to replace it but failed, the motherboard got/was damaged. (pretty common failure to laptops due to greedy companies soldering the jack directly to the motherboard with no additional support).

    The laptop can still run on the battery as it is a separate circuit. Therefore I would like to hook up a DC power supply to the battery. This gets complicated because of the additional data exchange between the battery and the laptop.

    So I am trying to remove the Li-Ion cells from the battery and connect a power supply. I can only draw the visible part of the battery setup, and I can only guess the output of a single cell, but most likely your guesses are better:

    https://drive.google.com/folderview?id=0B-0UNw6xiR-aWHpJUjlkMzZOWEE&usp=sharing (for pictures, could not upload on the forum :O kept getting errors)

    upload_2016-2-28_20-15-37.png

    Here are the questions:
    - What does MV and JV stand for ? this might help figure out what the PCB does with this inputs (note that blue one is actually white, and this 2 wires are also physically thinner then the black and red).
    - How could I replace the Li-Ion cells with a DC power supply (or two) and trick the PCB into thinking it always has 100% full battery, and what would be the required stats of the DC power supply?
    - Would it be possible to use the original laptop power supply, It is a 19V 9.5A 180Wh monster while the battery overall output is 86,6Wh ? (Like having a mega battery)

    Any thoughts are much appreciated,
    Thanks.

    *Fixed the diagram.
     

    Attached Files:

    Last edited: Feb 28, 2016
  2. alec_t

    alec_t Well-Known Member Most Helpful Member

    Joined:
    Jul 10, 2011
    Messages:
    9,283
    Likes:
    1,222
    Location:
    Cardiff, Wales
    Welcome to ETO!
    MV and JV are nodes which the charge/discharge ciruit monitors to ensure that over-charge and over-discharge don't occur and cause a fire risk.
    BTW the centre 3 cells are shown with reversed polarity.
     
  3. cowboybob

    cowboybob Well-Known Member Most Helpful Member

    Joined:
    Oct 22, 2011
    Messages:
    3,037
    Likes:
    478
    Location:
    James Island, SC
    Welcome to ETO, P.Vlad!

    MV and JV leads may also be involved in "balancing" the recharge of the battery sets.

    Read this thread and see if anything clicks with respect to your situation.
    http://www.electro-tech-online.com/threads/power-laptop-with-ac-adapter-through-battery-port.89885/

    As you can see, in some cases, the Brand of a laptop has a bearing on your question (some laptops look for a very specific battery ID before they will operate correctly).

    Get back to us if you're still unsure.
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. Les Jones

    Les Jones Well-Known Member

    Joined:
    May 15, 2015
    Messages:
    1,451
    Likes:
    189
    Location:
    Lancashire UK

    Hi Alec,
    I disagree with you on the centre three cells being reversed.

    Les.
     
  6. P.Vlad

    P.Vlad New Member

    Joined:
    Feb 28, 2016
    Messages:
    2
    Likes:
    0
    Hi All, thnx for the replies,
    maybe I can rephrase,

    what would be the voltage on JV and MV when the battery is full?
    or is it that only the potential difference between JV and MV matters?
     
  7. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,515
    Likes:
    942
    Location:
    Canada, of course!
    A normal Lithium cell is 4.20V when it has at a full charge. It is not "full" of anything.
    Therefore if -V is 0V then JV is +4.2V, MV is 8.4V and +V is 126v when the battery has a full charge.
     
  8. alec_t

    alec_t Well-Known Member Most Helpful Member

    Joined:
    Jul 10, 2011
    Messages:
    9,283
    Likes:
    1,222
    Location:
    Cardiff, Wales
    Post #1 has since been edited. The original circuit (to which I was referring) is in the post #1 attachment.
     
  9. Les Jones

    Les Jones Well-Known Member

    Joined:
    May 15, 2015
    Messages:
    1,451
    Likes:
    189
    Location:
    Lancashire UK
    Hi Alec,
    I didn't think you would get something like that wrong. I must have looked at the picture before its was corrected. I have also noticed that I must of missed the comment in post #1 "*Fixed the diagram" Sorry about that.

    Les.
     
  10. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

    Joined:
    Oct 30, 2010
    Messages:
    9,935
    Likes:
    1,099
  11. Les Jones

    Les Jones Well-Known Member

    Joined:
    May 15, 2015
    Messages:
    1,451
    Likes:
    189
    Location:
    Lancashire UK
    My feeling is this is beyond the ability of the OP as he could not even work out the voltages on the tapping on the battery that are used to monitor individual cell voltages.

    Les.
     
  12. fishkur

    fishkur New Member

    Joined:
    Oct 30, 2017
    Messages:
    2
    Likes:
    0
    Sorry to dig this up, but I have the exact same battery with the exact same problem. Had the same thought about fixing, hence ending up here.

    Curious if a solution was ever found, though I doubt it looking the the OP post count.
     
  13. Diver300

    Diver300 Well-Known Member

    Joined:
    Oct 19, 2007
    Messages:
    3,078
    Likes:
    101
    Location:
    England
    I would suggest three separate, isolated, Li-Ion chargers, one across each parallel group of cells.
     
  14. fishkur

    fishkur New Member

    Joined:
    Oct 30, 2017
    Messages:
    2
    Likes:
    0
    True, maybe just keep the cells topped up with an external charging circuit. Actually, am I overthinking the smart battery setup? Can I just ditch the Li cells and supply 4V with dummy cells...or will the SMBus sense that something is amiss?
     

Share This Page