The general lifespan of a Lithium Ion (Li-Ion) battery strongly depends on its age and usage. Because of this, most older laptops suffer from decreased battery capacity. A new battery pack (type: fpcbp17) for this specific laptop however can be difficult to purchase and expensive if you happen to find one. This article describes a simple, effective way and relatively cheap way of replacing the internal accu cells of this pack, reusing the charge logic and casing.

Warning: Dismantling Lithium-Ion (LiIon) accu packs can be potentially dangerous! LiIon cells are extremely sensitive for overheating causing explosion danger. Do not solder, or grind the cells more than necessary (1 second will do). Charge the reassemlbed pack in a safe environment first!

See the movie of an exploding Li-Ion accupack!

The specifications of the Lifebook B142 / B112 battery are the following:

type: fpcbp17
voltage: 10.8/3200mAh

You need the following tools:
* soldering station, preferably with a variable temperature
* tin
* some pieces of signalling wire
* small iron saw, or dremel multi-tool

The original batteries were of type LG18650P but I had difficulties purchasing exactly the same type in Europe. Luckily, other types will do the job just fine, or probably even better as they might have a higher capacity. Mounting this higher capacity batteries should be no problem, as long as the electrode material is the same. Depending on the material (graphite, in this case) the output voltage is different (3.6 to 3.7 volts). As a consequence, the charge logic should also be different (charging with 4.1 or 4.2 volts). Charging a 3.7V battery with 4.1V should not be a big problem, but doing the opposite: charging an 3.6V battery with 4.2V leads causes overcharged cells. Therefore you have to make sure not to exceed the 0.5V charge difference.

I purchased the batteries from an Ebay store run by a dutchman in Shanghai. These are Li-Ion cells of the type CGR18650D, made by Panasonic. They have a capacity of 2350 mAh, which is much more than the 1600 mAh (3200/2) of the original cells, leading to much longer battery life. You can find the datasheet of the CGR18650D cell here.

Start with opening up the old battery pack. There aren't any screws unfortunately, so you have to force it open. Be careful not to damage the cells or the charge logic inside. I used a dremel multi-tool, but a iron saw can also do the job. Start at the corners first, and work to the inside. After that you can remove the top of the casing. The cells and the chargelogic should be separated from the case together. Be very careful as the charge logic has a very thin pcb that can break very easily. When this is done, you can desolder the 3 wires from the charge logic. Write down what wires is supposed to go where...

The new cells don't have any lead to solder the wires to, and it's difficult to solder directly to the terminals. Therefore, I needed to grind off a little bit of the metal of the terminal. I again used the dremel tool for this. Pay extra attention not to overheat the Li-Ion cell by grinding to long. I also used in little protecting household pan in case of emergency. I guess you can't be too cautious here.

The original batteries were packed quite tigthly in the battery case, so there isn't much room for extra wires. The batteries should also be fysically connected (not just electrically). I soldered on of the wires a little to the side of the cell, and the positive lead directly to the terminal.

This procedure should be repeated for a series of three batteries first, then for the other series of three batteries. Finally the two series should be connected as well to get the double capacity (2 x 2350 mAh = 4700 mAh) and the same voltage (3 x 3.6V = 10.8V).

Next is to connect the leads to the terminals of the sixpack. This is relatively simple procedure. Fortunately you wrote down which wire is supposed to go where on the charge logic.

Now you can solder the charge logic, cutting of the wires to the smallest possible length. Be very gentle with the pcb. Also check if the position of the connector of charge logic matches the gap in the case.

The last step is re-assembling the battery pack. Don't use to much force when reinserting the cells. If there isn't enough space, it simply will not fit and the charge logic will probably break. You will have to check where the bottlenecks exactly are. Unfortunately the case cannot be restored in its original shape so you have to use your imagination for this. I used scotch tape, which isn't probably the best solution, but it did the job for me.

I charged the batteries for the first time in the open air, as I didn't know what would happen. Luckily, everything is okay. When booting my Linux operating system, the capacity wouldn't first exceed 74% but gradually went all the way up to 99%. Linux reports the battery life starting at over 1000 minutes, but almost immediately drops to about 280 minutes, which is over 4 hours, and again quite pleasant to work with.

1. Introduction
2. What you need
3. Opening the old battery pack
4. Soldering the cells
5. Reassembling the battery pack

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