HP/Compaq nw9440 Battery - 6 to 8 cell conversion

I bought 3 battery packs for my HP/Compaq nw9440 on eBay for a very good price due to the discount for buying 3. However, when they arrived, I found that they would not charge beyond 35%, even if left overnight.

Looking carefully at the tiny print on the original HP battery, I saw that it was 14.4V and that the batteries I had bought were only 11.1V, also that the new ones only weighed 3/4 of the HP one.

I contacted the seller with full details but got this reply "Dear friend, Thanks so much for your good news, what can I can I do for your now?" so as the time/packaging cost/risk of sending them back seemed not worthwhile, I thought I would see what I could do as a project.

I carefully cracked the case open of one of them, and they are 6-cell, with 2 empty slots for another 2 cells. The Li-Ion protective charge/discharge circuit board is marked with 0V, 4V, 8V, 12V & 16V connectors, so it's obviously designed to be able to take 8 cells.

However, although the 0V, 4V & 8V connectors are connected to the cells as expected, for some reason the 12V cell lug is connected to the 16V PCB connector, with the 12V PCB connector blank.

The next 2 things were to crack open a second battery and add 2 of the (same batch?) cells to the first battery, then (1) connect the 16V PCB to the 16V battery lug and (2) connect the 12V PCB to the 12V battery lug as well.

There is no sign of short-circuiting/heating/etc and the output terminals of the altered pack now have the same voltage as the original HP pack (actually slightly less, as I am working with the new batteries run down to indicated "0%" for safety).

But both times (1) & (2) when fitting the pack to the nw9440, it reported that the battery was "installed, 0% charge, not charging". I suspect there must be some jumper link/resistor somewhere on the board to change the configuration so that the Li-Ion protective charge/discharge circuit board doesn't think there is something wrong with its expected "8V to 12V" 4-volt cell being 2 cells totalling over 7 volts.

On the board, there are two 8-pin chips "4825P ACFFAF" and a 38-pin chip "SH366000AX 00021 N9W99".

Can anyone give me any clues what to try next?

Maybe I should just buy an 8-cell pack (at 4/5 of the price that I paid for these 3 packs!) and make myself a mega capacity pack by using 16 of the cells I already have to make it a 24-cell pack?

Thanks!

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HP/Compaq nw9440 Battery - 6 to 8 cell conversion