Hardware - How to change the CMOS battery of an Acer Aspire E5-521 laptop

One day I noticed that my laptop didn't save the time, so I was almost sure that the CMOS battery was dead. To fix it I had to open the laptop. To do this I used a magnetic screwdriver set, which can be found on Amazon:

Once opened, the laptop looked like this:

I had to remove the mainboard completely to access the battery, because it was behind:

To my surprise, the battery was soldered, so I had to use a soldering iron to remove it. I ordered the battery on the Internet, it was a rechargeable 3V ML1220. In this video you have more info on how to do it.

Once I changed the battery, I also cleaned the fan well and put new thermal paste on the CPU. It's very important to use a good thermal paste to keep the CPU cool. I use Arctic MX-4:

Finally I assembled the laptop and checked that that it worked. Yes, the operation was a success, now it saves the time.

In case you have more doubts, here you have a full video showing how to service this laptop.