The controllers must be matched to the batteries, particularly in a lithium-ion pack. More than with any other battery chemistry, lithium-ion requires very special handling to avoid overcharge (and over-discharge). If you change the cell type, you will make erroneous the controller's assumptions about what electrical terminal behavior corresponds to a given charge state. This could be Ghostbusters bad.
If you can find cells with the same ratings as the original, and you still want to proceed with a recelling operation, it isn't particularly hard, but you must observe a couple of rules to ensure safety:
1) Never short the cells.
2) Make sure that you connect the cells exactly as in the original (you knew that, I know).
3) Do not solder the cells. Use a spot-welder to connect the tabs together. Lithium-ion cells are exceptionally intolerant of heat.
If the cells were ever over-discharged, some controllers will set a nonvolatile bit to prevent recharge. Even after recelling, the controller may refuse to initiate a charge cycle. If none of this deters you from recelling, and you get stuck at this point, post again, and I'll outline a "CPR" procedure (it is a bit scary).
If you can find cells with the same ratings as the original, and you still want to proceed with a recelling operation, it isn't particularly hard, but you must observe a couple of rules to ensure safety:
1) Never short the cells.
2) Make sure that you connect the cells exactly as in the original (you knew that, I know).
3) Do not solder the cells. Use a spot-welder to connect the tabs together. Lithium-ion cells are exceptionally intolerant of heat.
If the cells were ever over-discharged, some controllers will set a nonvolatile bit to prevent recharge. Even after recelling, the controller may refuse to initiate a charge cycle. If none of this deters you from recelling, and you get stuck at this point, post again, and I'll outline a "CPR" procedure (it is a bit scary).