Laptop Complementary Metal Oxide Semiconductor CMOS battery and its faults with diagrams

Explanation of everything related to the laptop's CMOS battery and its faults .Real Time Clock (RTC)

1. Complementary Metal Oxide Semiconductor battery

The rated voltage of this battery is relatively 3.3 volts

2. Working principle

The Cmos battery supplies the board with a voltage of 3.3 volts while the computer is turned off, while the same voltage value comes from the mainframe of the computer when it is running.

4. Analyzing the Real Time Clock (RTC) circuit diagram.

Picture of the scheme

- Schematic analysis:

The diagram shows the circuit and its components consisting of resistors, diodes, capacitors, etc.

- The first step in removing the damage is to replace the battery with a new one and make sure that it is working, how is that to make sure that the clock and date remain set after turning off the computer and turning it on again.

If the first step does not succeed, we proceed to the following:

- The second step

Examine the components close to the battery socket or use its scheme, as in our case, to find the source of the damage.

5. Electronic items to be checked in the circuit:

All suspicious electronic items that you colored yellow must be checked as shown in the diagram. These elements are detailed:

RTC Socket CN5

Transistor Q27

Resistance R215

Resistance R254

Diode D15

Diode D16

- Capacitor C222

Of course, after examining these elements, especially the integrity of the socket, the transistor and the diodes, we must make sure that the activation signal called RTCRST # _EC arrives. This signal is coming from one of the big IC KBCs called KeyBoard Controller.

An illustrated picture of the schematic

 It should be noted that among the CMOS battery faults that constantly occur, is that while trying to turn on the computer, the screen appears black and the computer is on or the computer does not operate at all. In this case, we must take some steps in order to address the problem, and these steps are:

- We remove the computer battery and also remove the power cable, ie all the power sources that supply the computer with electrical current. Then we press the power button for about 30 seconds until all the excess power on the motherboard is discharged, after which we return the power cable or the battery or both together and turn on the computer.

It should also be noted that the schemes adopted in this article are diagrams for the Acer computer. We adopted them for explanation, but the principle is the same.

For those who want more details and more explanation, welcome to your comments.