Where are laptop batteries made?

Circuits never die. It locks itself and sets itself "Permanent Failure" flag then blows the fuse when it dedected some issues,like when 1 cell died in battery. one died cell will make battery extremely unbalanced , it will heat pretty much then battery will lock itself

Same thing can happen when battery is over discharged. Or when you overload the battery. It will blow fuse , then battery will enter pf mode.

And last warnings ; the battery can die even when upgrading firmware of battery (especially lenovo / IBM batteries with custom firmware ).

If you have a Lenovo/IBM battery. Dont try this. It will OK to disconnect cells . but when you reconnect new cells , it will enter pf mode and blow the fuse when you triggered a power reset of circuit / smb controller.

And when you trying to recell a battery , first disconnect GND at end of the cells , when you builded all cells , connect GND last. Because removing gnd will immediately power down battery controller. If you disconnect cells randomly , battery will dedect imbalanced cells and it will enter the permanent failure mode.(And if you have a battery with a external eeprom (like bq2040/2060) backup eeprom first in case battery gets locked , just rewrite backup to battery then powercycle the circuit)

Sorry for long post and bad english. These are all my information about SBS 1.0 and 1.1 compatible batteries.

The notebook battery pack has a microcontroller in it to manage the charging and discharging. It is not only controls the power flow from charger and to the computer, but also safe guards the process to avoid overcharge/over-drain and overheat the pack. The pack is talking to a embedded controller in notebook through SMBus to manage the power flow.

There are two different approach the manufacture take for protections:
1) When a fault condition happened, cutoff current flow until the condition is removed.
2) When a fault condition happened, cutoff current flow, register the fault and disable the battery until the battery pack is reset.

One of the fault is: If the battery cell(s) voltage is dropped under a preset level, lock up the battery circuit to prevent them being charge and discharge. This fits exactly the condition as when you remove the old battery cells to replace with new cell(s). That is why the pack failed after replacing cells. When this happen, the type 1) battery may allow a very low rate to charge the pack for determining if it is a "short" condition at battery or just a over-drain. If it is not a short, the pack will recover after "hours" of low current charge and bring the battery pack back to alive again. However, the type 2) will mark a bit in the microcontroller EEPROM memory and lock it up to prevent being charged or discharged so it won't cause further damage. The pack became "dead".

In case of the over-voltage condition on cell(s), the pack may has a fuse as the "secondary protection". The fuse is blow not by the "over-current" rather break by intentionally heating the fuse to make it "burn". (this type of fuse has three terminals and a "heater" resistor in it) If this fuse is blow, the pack is bricked. The over-voltage may happen if you charging the cells without monitoring voltage on each cell-sets carefully. (Or, think higher voltage will charge faster). This fuse normally is located between MOSFET and highest cell terminal, or MOSFET and the positive pack terminal.

The re-celled pack also may need to have a jump start. This is for restart the microcontroller after lost power by removing cells. The jump start is done by apply a voltage at pack positive terminal. You may seen this method on some blog or YouTube clip by shorting from battery positive to pack positive terminal.

Most of the battery packs do have a usage counter to track the charge/discharge cycles. It is recorded in the EEPROM memory as well. And, some of them also use it to reduce capacity or lockout pack after certain count. Replacing the battery cells does not reset the counter normally. A special software and/or a fixture will require to do so. The SMBus at battery pack interface can be used to unlock the battery pack. However, most of time you would need a adaptor to do so. And it likely is password protected which be difficult to break-in. So, after re-pack, it may still at the same condition as before.

Therefore, doing this hack may kill the remaining life of your low flow battery pack. It is also dangerous trying to maintain the power on the pack while replacing the cells for bypassing these issues. (Especially when soldering is required). A short can cause fire or damage the PCB in the pack. All these protection measures have their purpose.

Play safe!