Connect with us

Laptop battery fix

Discussion in 'Power Electronics' started by bushtech, Mar 12, 2021.

Scroll to continue with content
  1. bushtech

    bushtech

    1,013
    157
    Sep 13, 2016
    laptop.jpg
    Opened my laptops battery. All batteries read about 4.08V apart from Batteries 3-4 and 11-12 which read 1.48V and which I want to replace.This battery pack now unobtainium from manufacturer. So 6 batteries for 11.1V 5200mAh and 56 Wh. How do I figure out what maH these individual batteries are? 5200/6 = 867mah? Seems rather low
     
  2. Bluejets

    Bluejets

    4,604
    977
    Oct 5, 2014
    bushtech likes this.
  3. dave9

    dave9

    1,027
    271
    Mar 5, 2017
    6 cells, nominal 3.7V each, so 11.1V/3.7= 3 in series
    6 cells / 3 in series = 2 parallel runs of 3 in series
    2 parallel to reach 5200mAh = 5200mAh/2 = 2600mAh per cell.

    You do not need to get 2600mAh rated cells, could use a bit higher or lower, and remember that was only their original rating not the now old degraded capacity remaining so even if you bought a couple 2600mAh cells, they won't match the rest in true capacity.

    You should replace all 6, same make/model, should use decent major brand capable of (ideally) over 10A drain rate.

    However once you rebuild the pack, you will probably need to run a calibration routine in your laptop bios or windows app to get the right runtime estimates for the new pack.

    That kind of math is mostly reserved to crappy chinese jumpstarters and power banks. Any pro battery pack from a reputable company should be rated like the laptop, or tool batteries, etc are, where it is the mAh capacity at the series voltage it outputs. Unfortunately the madness is spreading, more reputable companies are now considering rating in this unorthodox manner to try to look competitive with the faux generic product specs.

    There are some generic brands making a compatible C4500bat-6, but unless you find someone who did a teardown, there is no assurance ahead of time about what cells are in it, even whether they are new or used, so buying major brand cells from a trusted source to rebuild yourself, is the surest way to end up with a better capacity and lifespan.
     
    Last edited: Mar 12, 2021
    Harald Kapp and bushtech like this.
  4. bushtech

    bushtech

    1,013
    157
    Sep 13, 2016
  5. bushtech

    bushtech

    1,013
    157
    Sep 13, 2016
    @dave9 Max. continuous discharge (Continuous)15A(at25°C), 60% at 250cycle
     
  6. dave9

    dave9

    1,027
    271
    Mar 5, 2017
    Those should work, though I might see if I could find some cells with tabs already welded on, unless you have a spot welder to DIY as you're not really supposed to solder directly to the cells themselves.

    I mean I am assuming that is how the original pack was set up, don't see any battery contacts for each cell or at the ends built into the casing?
     
  7. bushtech

    bushtech

    1,013
    157
    Sep 13, 2016
    Yep, the old batteries use tabs but not really fussed as I've soldered leads onto 18650's successfully many times.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-