When i turned on my computer message RTC battery is low or CMOS checksun is inconsistent press f11 key to set date i have tryed f11 and had it pluged in all night still same message.

The RTC battery is a rechargeable Li-ion "clock" battery that's buried underneath the keyboard - it keeps date and time going when your computer is turned off. If you're getting this message, you should go follow the screen prompt, hit F1 to enter Setup, and set the date and time, leave the computer on for several hours to charge it (the clock battery recharges only with the computer turned on) and it should go away.

In the rare event that your RTC battery is bad, it's really up to you as to getting it replaced or not - it's a lotta work, and not all the battery vendors out there is competent enough to sell you the right kind of battery (installing a non-rechargeable Lithium battery will kill the thing outright, and there are actually people selling these....). Not having a working RTC battery doesn't really interfere with the workings of the computer - you'll just have to set date and time every time you start it, and you can do so manually or by downloading some freeware such as Atomic Clock Sync to automatically do it for you.

You need to replace the CMOS battery and reset the BIOS information.

I received an IBM laptop with same issue a few months back. The error message due to the drained out CMOS RTC (coin-cell battery), which retains and other BIOS settings.
The system is OK and all you have to do is to get the CMOS/RTC battery replaced by the a professional.
Good Luck!
CreativeTECH

Your RTC battery or CMOS battery is either dead or too low to keep the correct settings, windows will not operate correctly without the proper date and time kept. This battery has to be replaced for your system to operate. Below is the service manual that will advise you of the proper procedure to replace the battery. Once the battery is replaced, reboot the laptop, go to the BIOS screen and reset the date and time, then reboot as normal. In the case of your particular laptop, the laptop has to be disassembled down to the lower case and motherboard. The included service manual has the procedure for this.

http://tim.id.au/laptops/toshiba/satellite%201400%201405.pdf

hi friend,

Probably a dead Motherboard battery. Need to enter the BIOS screens and reset values. Especially the time and date. Maybe the boot order and if using USB KBoard enable legusy USB devices. This will occur each time your friend shuts down and reboots until the battery is changed.
Issue
When you turn your Toshiba computer on, you see an error message like: **** Bad RTC battery ****
**** Bad Checksum (CMOS) ****
Check system, then press [F1] key The Real Time Clock (RTC) battery provides power for the internal clock/calendar and for maintaining system configuration settings.
This error can occur when a machine has been left turned-off for an extended period of time (around a month), and is the result of a depleted RTC battery. Other symptoms include not being able to execute Windows Update properly, errors/problems executing application software (like Norton Antivirus), and the appearance of the Windows XP "Desktop Clean Wizard".
Resolution This condition is easy to fix in 3 basic steps: Reset the BIOS defaults
Set the correct date and time in Windows.
Charge the RTC battery Please follow the detailed instructions in the next section.
Procedure Set BIOS defaults Press the [F1] key as instructed in the error message:
**** Bad RTC battery ****
**** Bad Checksum (CMOS) ****
Check system, then press [F1] key In the BIOS setup screen press the [Home] key to restore the default values, then press the [End] key to save and exit, then the [Y] key to confirm and restart the system. Set the correct date and time in Windows As Windows starts-up, you may see an error message about an "Invalid System Time". Go ahead and click "OK" to clear the error dialog. Open the Windows Control Panel and open the "Date and Time" control by double-clicking its icon. Set the correct date and time, then click OK to save. Charge the Real Time Clock (RTC) battery To charge the RTC battery, connect the AC adapter and turn the computer on (both the DC IN and Power LEDs must be green). Leave the machine on for approximately 24 hours to ensure a full charge in the RTC battery. Please note that the RTC battery does not charge while the PC is turned off, regardless of whether the AC adapter is connected or not. Other Information: If, on subsequent reboots, the "Bad RTC Battery" error persists, it's quite likely that you actually do have a bad RTC battery. If that's the case, you should contact a Toshiba Authorized Service Provider to have the system serviced. Windows XP Desktop Cleanup Wizard The first time you reboot Windows XP after resetting the system clock, Windows XP may try to run the "Desktop Cleanup Wizard". Simply Cancel the "Desktop Cleanup Wizard" at the first dialog. If you do manage to clean your shortcuts from the desktop and want to recover them, you will find them in a folder called "Unused Desktop Shortcuts". You can recover them as follows: Double-click to open the "Unused Desktop Shortcuts" folder
Click to expand the "Edit" menu, and click "Select All"
Drag the selected items back to your desktop
Close the "Unused Desktop Shortcuts" folder. You can delete this folder if it is empty.

thank u for using fixya

regards,
sivaranjini

That means that after computer had been off for a long time the CMOS battery has drained, and CMOS (BIOS) settings had been reset to default.

Usually the computer will work fine after pressing F1, but you may get wrong date and time.

Try charging battery completely, often the problem disappears, if it does not , then the choice is between pressing F1 each time you start the laptop, or disassembling the laptop and replacing CMOS internal coin battery, located on the lower side of the motherboard.

Hello

Please reset cmos to factory defaults.
Then enter the bios setup and configure it and save changes.

I'd look at trying to replace the BIOS battery...
Check out this guide for dis assembly instructions :
http://www.irisvista.com/tech/laptops/Toshiba_Portege_R100/remove_system_board_1.htm

This is the REAL TIME CLOCK power supply inside your laptop.It maintains the system configuration and clock/calendar. Do not try to replace this yourself unless you are experienced,you could lose everything on the system and worse still these batteries can explode!! Connect the AC adaptor and let it charge for at least 24hrs. Press F2 to enter the bios. Set correct time and date If it Persists take it to a dealer to be replaced

plz try by changing the cmos battey