The HP DV4 (and similar models, not sure what all interchanges) have an optional extended 12-cell battery. The originals were rated as 8800mAh, which works out to 12 2200mAh cells inside - I bought a lightly used pack and opened it, found 12 LG 2200Ah 18650s, all in good condition. But used packs are always a crapshoot, especially if you know nothing about how it was treated in its former life.
So completely by accident I stumbled across *new* aftermarket DV4 packs on ebay, with an upgraded capacity (advertised, unconfirmed) of 9600mAh, which meant that if true, there should be 2400mAh cells inside. And the price with free shipping is, somehow, under $30. What?!
I bought two, and cracked them open. They may be complete garbage when used as intended as a laptop battery, but who cares about that, right? Here's what you'll find inside...
One thing to note, there was a sticker on the PCB inside that said "DV4 8.8AH", which may mean nothing fishy going on with the 9600mAh advertised rating. The internal circuitry would be the same whether the cells used were 2200 or 2400mAh, and these could have been from the same batch used to build the 8800mAh packs. Without identifying these particular cells, I'll never know.
From what I can figure '6K00112' is the model (I have 6 CJ cells from a different pack, and they are marked 6E00312) and CJ is the manufacturer... but I have no info on who or what CJ is, other than some hits for similar cells on alibaba and the like.
All cells from pack #1 were at 3.84v after they were all separated; pack #2 cells were 3.80v. All 24 charged up just fine in a XTAR WP6.
And finally, a tip for my fellow cheapskates who like cracking open laptop packs. Get yourself some of these:
Outside snap ring pliers, most commonly used for things like retaining syncros/gears/bearings on transmission shafts (remnants from my previous incarnation as an auto tech... *shudder*). Once you break open a small spot between the two halves of the casing, stick the pliers in and squeeze. POP! POP POP! And the pack is opened. No Dremeling, no hacksaws, no poking holes in the cells trying to use a screwdriver. Couldn't be easier, and on top of that you're much less likely to damage the goodies inside. Win/win.