Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Laptop battery rebuilding

  1. Jun 19, 2011 #1
    So I am in the process of rebuilding my laptop battery for higher capacity cells. I would appreciate it if someone can help me understand the arrangement of the cells. From my research, each cell is 3.7V 1800 mAH Li-Ion cells. There are 6 of them in the battery pack. In this arrangement:


    Untitled.png

    I will guess and say that the VP is receiving 7.4v and VG is the ground. But why is VH and VM receiving both positive and ground of 14.8v? And what do they stand for?
     
    Last edited: Jun 19, 2011
  2. jcsd
  3. Jun 19, 2011 #2
    I think you should redraw the circuit on paper so its easier to understand, you should see what's going on better.
     
  4. Jun 19, 2011 #3
    It is exactly how I drew it on the image above. From what I see in the battery case, there are wires going from the battery terminals to VH, VM, VP, VG which are solder points on the circuit board. I'm just trying to figure out how can one input receive both + and - ?
     
  5. Oct 28, 2011 #4

    bam

    User Avatar

    pardon me for posting to an old thread, but i came across this in a search...

    i'm a little confused by your diagram. i don't understand how it would be putting out 14.8v. if your battery is putting out 14.8v i would think you have 4 cells, or pairs wired in parallel then, wired in series (4 * 3.7 = 14.8) do you mean 11.1v?

    VM & VH would be used for balancing afaik. if it's an 11.1v battery, VM would be between the first and second cell(s) in series, and would read 3.7v. VH would be between the second and third, and would read 7.4v. then measuring the VP (B+) you would see 11.1v.

    those numbers would be appox. if an individual cell is below 2.8-3.0v it's possibly undercharged. above 4.2-4.3v it's possibly overcharged. so you may be getting a slightly different voltage reading.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook