Had a ruined Toshiba Satellite that I've already stolen most of the electronic components out of. The battery was good, was a 4s1p(14.4v) Li-Ion pack with an onboard charger in the housing. I disassembled the cells and re-assembled them in a 3s1p configuration. I pulled the charger and re-wired it to use one Deans connector to charge in 11.1v while using a Blinky balancer to keep the cells in check. Much to my surprise a full discharge(on my Bantam E-Station BC6) and charge pushed 2600mah into the cells. Much higher than the rated capacity. Two of the cells are a perfect 4.2v max, the third is 4.15v which is acceptable. The fourth cell, the one left over, is also a 4.2v max so I may pull the weak cell in favor of it. The only modification I had to make to the Halo was trim a little tab from the battery door. Everything else fit. I had to leave some play in the pack because it had to go in at an angle. It doesn't just slide right in. The third cell has to be centered over the other two after they are clipped in so the door will close. Once in, the fit is perfect.
Disclaimer- Lithium batteries are HIGHLY reactive and extremely dangerous. If you cross the wrong wire, you melt your hand and burn the house down. They must be wired correctly and charged correctly or they will explode(most of the time they just melt and flame but explode sounds better). If you aren't excellent with a soldering iron and have a very good understanding of how these batteries work, I do not suggest you toy with them.