Laptop battery repair. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Laptop battery repair. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells

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The most vulnerable part of a laptop in terms of the number of failures is the battery. Despite the fact that you are using a regular AC adapter, the battery efficiency gradually decreases - less and less time is left for autonomous work. Eventually the battery will have to be replaced. But, the battery is a very expensive component, if a new laptop can now be purchased for $800 and much lower, then the battery costs about $200. And besides, infrequently on sale you can find exactly the battery that you need, especially if the laptop is already with age.

In fact, repairing a laptop battery is easy and inexpensive. The fact is that the same removable battery pack is not so much a battery as it is a removable unit. Inside this box there is a rather complicated and expensive electronic unit and the actual battery, made up of cylindrical Li-ion cells.

So, we remove the hopelessly discharged battery from the laptop. Then we open the case. This can be done with a mounting scalpel or a fitter's knife, very carefully separating the halves of the body. The knife should enter the case no deeper than 1-2 mm, otherwise its electronic filling may be damaged.

After removing the cover, we will see a printed circuit board connected to the battery compartment with three petal contacts and two mounting wires. This board is essentially a battery charger circuit, as well as a controller that monitors its condition. Usually with this board everything is in order. Problems are most often with the wear of the battery cells that are located near it. Without removing the elements, measure the voltage on them with a multimeter. The voltage on each element should be 3 ... 3,5 V (the battery is discharged), in any case, not be lower than 3 V.

Most likely it will become clear that the elements need to be replaced. At the same time, it should be taken into account that the newly installed elements must be of the same type as those that were before, both in capacity and in type. It is advisable to generally replace everything at once with elements from the same batch, or at least close in release date. Typically, "laptop" batteries use CGR18650HG, CGR17670HG, CGR345010G or similar cells for an operating voltage of 3 ... 4,2 V. Such cells are on sale charged up to 3,6 V. 3,1 V. As a discharge load, you can use a resistor with a resistance of about 10 ohms with a power of 10 watts. You can make a battery of five parallel-connected two-watt resistors of 47 ohms. Connect this load to the element and follow the multimeter for a decrease in voltage.

I do not recommend installing charged cells, as this will lead to a malfunction of the PC charger (in the same board). When connected, the board will try to charge them, but there will be no charging current. and this despite the fact that the memory of the board has data that the battery was discharged. As a result, there are two possibilities. Either the controller decides that the battery is defective, or there will be a malfunction in its program, due to which it will accept this level as discharged, and the charging process will be disrupted, which will lead to overcharging of the battery cells. Of course, this may not happen if the electronics of this particular battery is smart enough, but it's not worth the risk.

So, the elements have been prepared, now we will change. Old elements must be disconnected from the board in a certain order - starting from plus to minus, and the installation of new ones must be carried out in the reverse order. That is, when installing new elements, the element associated with the common minus is first connected, then we connect the remaining elements in series.

Now that everything is checked, you can assemble the case and fix the cut cover. The method of attaching the lid can be on plastic glue or simply wrap it with one layer of adhesive tape.

Perform the first charge by carefully monitoring the temperature and sniffing the battery for a burning smell. If something is not right, immediately turn it off - it is possible that the elements were connected incorrectly or the charging controller board was damaged (if the case was opened carelessly).

Author: Antipov A.P.

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