BIOS time resets to 1985 when battery runs out?

[fleamourian]

My ThinkPad sometimes left unattended runs down the battery completely, & then has the annoying habit of a long hang then having to enter BIOS to reset the time/date. I thought replacing the CMOS battery would solve this, but it didn't. Should I have charged the CMOS battery first use? I just replaced & used laptop as normal, it is one of these eBay batteries.

[RealBlackStuff]

Quite possibly a dud eBay battery.
Use a multimeter to check that the CMOS battery has 3.0Volt. If not, get another one.
Use the + on the red wire and the - on the black wire of the battery.

[nikki605]

Replacing the CMOS battery should have fixed it. After replacing the battery, you should have only had to set the BIOS clock one time.

I would double check the battery's voltage with a voltmeter at the connector to make sure the wire pigtail has a good connection. Make sure that the plastic connector is firmly seated on both pins. Lastly, (and the hardest) you may have to open up the TP and remove the system board to inspect the two CMOS battery connector pins - make sure they are both still soldered to the board. There have been reports of solder cracks or broken pins.

[fleamourian]

Just to check, the little white plug can only be inserted one way, yeah? I have black wire on the right & red on the left. Have arranged to go round a mates Mon/Tue & borrow his multimeter.

[RealBlackStuff]

correct.

[fleamourian]

Left battery charging for 16 hours & no problems so far!

[rkawakami]

The CMOS (backup) battery is not rechargeable. It supplies the proper voltage (3V) until it isn't able to do so; somewhere around 7 years on average.

[fleamourian]

Well that's what the eBay supplier also states:

"...these are not by design made to be rechargeable. Seems that the eeprom chip requires that they are not rechargeable, as in those days of the manufacuturing as you state the year of the eeprom firmware date of 1985 would indicate the battery has lost it's effective voltage in maintaining the firmware and clock settings in the bios. So with the basic input/output firmware (bios) not set, one should first check the battery voltage on the cmos backup battery and then if the conclusion is that the voltage is lower than +2.5v, the current won't trigger the Amtel eeprom chip...Although we do test these for voltage at incoming and prior to post, first lets make sure on your end that it does test as it should, 3.3v or higher. This way we know if their is not a hardware failture in the Amtel chip."

Maybe if I leave the laptop with flat battery for 16 hours odd then try booting.

[Robbyrobot]

Maybe if I leave the laptop with flat battery for 16 hours odd then try booting.

Why would you do that? If the CMOS battery is low or dead, it has to be replaced. All it is is a CR2025 or CR2032 cell in a holder - I pull off the metal straps welded onto the battery as contacts with pliers and use plastic electric tape to attach them to a new battery. Never had any problems, although many people don't recommend this method.

At any rate, you're going to have to check the voltage of the present CMOS battery with a cheap multimeter (should be 3.0 volts or slightly above) to see if the battery is bad (which is probable) - there's no other way to proceed. Charging the main battery won't have the slightest effect on the CMOS battery.

[fleamourian]

Yes, you are right. The eBay seller has replaced it with a branded battery, Panasonic, rated at 3.31v. The other was only registering 'bout 2.5v & was unbranded. I have a box of CR2032 batteries lying around. Maybe try that trick one day.

[doctor bloomquist]

These eBay CMOS batteries are only good for 1 trip. Make sure you get a couple or next boot the time displacement circuits will be fried and you'll be stuck in 1985! Stranded with stonewashed jeans, keytars and shoulderpads!

[Robbyrobot]

These eBay CMOS batteries are only good for 1 trip. Make sure you get a couple or next boot the time displacement circuits will be fried and you'll be stuck in 1985! Stranded with stonewashed jeans, keytars and shoulderpads!

Don't confuse the poor guy, Doc. CMOS batteries from Ebay are no better and no worse than any others, and if the CMOS battery dies, nothing happens except that you have to enter the time and date every time you boot the computer.