Dell Latitude C400 laptop have. Yesterday, I found that the date and time is not changed after the system startup. I think there is some question as CMOS CMOS is updated the date and time, when the laptop turned off. I want to know how to replacethe CMOS battery. Please suggest. Thank you in advance. You must disable the laptop, then remove the chassis thelaptop, then find the location of the battery. Next is to carefully remove the battery because the battery on the motherboard of each seat is different, the method is to remove the battery there are many, there are three other common external button to remove the battery to the battery holder just press the button next to it, then start the battery. Check and reply. I have complete replacement. Save time and money, has also been the experience. I refer to the original battery BIOS asked where they answer me, I try to change themselves, they do not do it, and then ask him to change, and even then, first open the fan behind the board of directors, then the fan to remove the battery on the radiator, put the heat sink to open, replaced the battery, it is easy to fill. Dell laptops can contain additional internal battery of the clock power, CMOS, curriculum vitae and functions of sub-battery. Types range from button lithium batteries nickel-cadmium (NiCd) and Nickel Metal Hydride (NiMH). These can be welded directly on the system board (or sub-card) or attached using a wire harness and connector sub-Miniature. Locations of these devices vary from model to model, but in most cases, these devices are located under the keyboard. All the best. In general, the life of the CMOS battery is, but 5 years. you must open the keypad can see the CMOS battery, and has replaced the direct tension down. Nothing to do with the BIOS password. You must use extreme caution when you remove the keyboard on a laptop because the keyboard assemblies are connected to the system board in a flat “ribbon” cables. Check and reply. Your laptop must be booked at screw hole CMOS battery, which does not affect the seals, do not destroy the principle of quality assurance can take a screw, you use the appropriate screwdriver, take the screw to the appropriate Below, you can remove a small cover, remove the battery and put new on it. Do not be affixed to the screw-seal was taken down, it will destroy the joints, leading to the failure of your warranty. If the warranty period, you can change the backup battery as well. You can change themselves, but I do not understand your CMOS battery at that specific location of the machine, so I suggest you please aid professionals, such as suppliers or service center that specializes in the repair of laptop. The size depends on the person, and not necessarily the same laptop.