Laptop Battery Rebuild

Discussion in 'Community Discussion' started by velocityg4, May 22, 2008.

  1. velocityg4 macrumors 601


    Dec 19, 2004
    Just two months ago I bought some third party battery to replace an ailing one on my Acer Aspire 3000 series laptop. Well it has already failed, shows as charging but does not charge. I was going to replace the controller board on this new board with the board from my old battery since the old battery just had a severely diminished capacity, 10-15minutes.]

    Anyways once I cracked open the newer 8-cell battery I noticed that the two cells in group four had no voltage output while the other groups are steady at 4.14V. Now I am thinking rather than a bad control board that one of the batteries in group four was initially defective so when being used the one good battery must have been discharging faster and probably completely while the other groups were not causing the batteries ultimate failure. Though I do not know if the control board just did not charge/discharge the battery groups evenly since at each 4 volt grouping a negative lead runs from the battery to the controller.

    My plan now is to build a new 8-cell battery if I can find Lithium Ion replacements, I read some about rebuilding laptop batteries. But I want to use the charge controller from the old 4-cell battery since I know it is good. So would this work? The 8 cell group totals over 16v just like the 4-cell. However there is one problem each 8 cell group outputs 4.14V while each battery of the 4 cell is 4.17V. Would this difference be negligible and would the charge control board handle 8 batteries?

    8-Cell Battery

    4-cell battery

    8-cell controller

    4-cell controller
  2. 0007776 Suspended


    Jul 11, 2006
    I don't know enough about it to answer your questions, but if you bought the new battery 2 months ago why didyou open it up instead of having it replaced under waranty?
  3. RedTomato macrumors 68040


    Mar 4, 2005
    .. London ..
    You're asking on the wrong board. There aren't many EE here - ask in a specialist EE forum.

    I'm no EE but here are my thoughts: I think battery controllers monitor voltage levels, so two cells in parallel should look roughly the same as a single cell.

    Except of course, each cell may be slightly different, but the controller will only see the average of the two cells.

    The difference between 4.11 and 4.17 is negligible to this non EE. It's only 1.2 % difference. Your battery controller may taper off charging slightly too early or slightly too late, but it's probably no big deal.

    My final thought is that at the moment, you have two non-working batteries and a pile of components. If you can make a working battery, great. If it doesn't work, you've lost nothing by trying.

    One note of caution - don't leave it out of your sight while charging, as lithium batteries can be rather flammable if treated wrongly.
  4. velocityg4 thread starter macrumors 601


    Dec 19, 2004
    The U.S. reseller only guaranteed it for 30 days and the battery does not even list the manufacturers name. A google search on the serial number came up with a company based in some east Asian country, I have no clue as to which. There was no mention of warranty, support number and what appeared to be the online chat system was in some east Asiatic language. Since the battery only costs $45 it is not worth the trouble to wait weeks for a replacement.

    I am doing this rebuild for the fun factor.

    What I think I will do at the moment is to take the four good cells out of the 8-cell battery and align them like the old 4-cell battery then use the 4-cell controller. From further reading it seems that the controller is just a smart charger and possibly a voltage regulator. As for finding cells online all I can find are 3.7 volt cells which seems to be what most laptop manufacturers use.

    I am well aware of the fire hazard and will only have the battery installed while I am using the computer. Otherwise it will be stored in a less flamable location.

    Then again I may just use the cells for a really light and long life RC Car/Plane battery pack.
  5. Laptop Battery macrumors newbie

    Nov 14, 2010
    Hi! I had my battery rebuilt too but then I realized that taking care of our laptop battery is really necessary especially when you use your laptop almost 24/7. Nice post! Thanks for the heads up!

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