Understanding Cell Arrangement in Laptop Battery Rebuilding

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SUMMARY

This discussion focuses on the arrangement of 3.7V 1800 mAH Li-Ion cells in a laptop battery pack consisting of six cells. The voltage outputs are clarified, with VP providing 11.1V when measuring the total voltage of the series configuration. The roles of VM and VH are identified as balancing points between cells, with VM measuring 3.7V and VH measuring 7.4V. The conversation emphasizes the importance of understanding cell arrangement for effective battery rebuilding.

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  • Understanding of Li-Ion battery chemistry and specifications
  • Basic knowledge of electrical circuits and voltage measurements
  • Familiarity with battery management systems and balancing techniques
  • Experience with soldering and circuit board modifications
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cadaver
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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?
 
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cadaver said:
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:


View attachment 36565

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?

I think you should redraw the circuit on paper so its easier to understand, you should see what's going on better.
 
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 - ?
 
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.
 

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