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Is Your Clock Battery Losing Time?
Copyright © 1992. Barry A. Goldblatt. All rights reserved.
There are over 300 million computers in the US today and each one requires a battery of some sort to maintain the date, time and critical startup information. This includes computers manufactured by Apple, Dell, Hewlett-Packard and a host of of others.
It’s impossible to accurately predict the number of failures because of the wide variety of batteries and system boards used in desktops, laptops and file servers. Sooner or later, every system will require a battery replacement. Some batteries used in computers produced as late as 2000 are no longer made and require a retrofit replacement. Local availability can also an issue because retailers typically don’t stock a full selection. Still others provide replacements only when the customer pays a labor charge. Labor charges can vary from as little as $45 to as much as $125 for on-site replacement, plus the cost of the battery.
What Are Computer Clock Batteries?
Computer clock batteries preserve the computer's setup information as well as the date and time shown by the system clock when the system is turned off. Setup information can include the amount of RAM, the monitor type, hard disk drive specifications, peripheral addresses and system performance options.
Computer clock batteries can last three to four years or longer. This is true even for small lithium coin cell batteries. Some manufacturers use products from Dallas Semiconductor, BenchMarq, Odin, TwinHead, et al,. These are “smart” batteries and integrated clock battery/CMOS modules which can last up to ten (10) years. Battery life can be affected by circuit design, usage and temperature. High temperature is a leading cause of premature failure in computer clock batteries. Systems with high performance processors like the Intel 486 and Pentium, Motorola 68000-series, Motorola PowerPC series, a modem or network interface card (NIC) and a CD-ROM generate far more heat inside the case than their predecessors.
It’s also worth mentioning that some industrial computers and Macintosh desktop models draw AC power even when the system is turned off via the CPU power switch. If a Macintosh is left unplugged or the current is interrupted by a surge-suppressor that is turned on and off daily, the clock battery drains faster. Macintosh computers with a high-energy 3.6 Volt lithium battery (i.e. a Tadiran TL2150) will maintain system information for quite some time, even if unplugged. However, Macintosh systems that use the Rayovac 840 alkaline battery (the Performa series, for instance) may only last a few months.
How To Avoid Clock Battery Failure
ONE OF THE FIRST WARNING SIGNS OF COMPUTER CLOCK CMOS OR PRAM BATTERY FAILURE IS A LOSS OF TIME BY THE SYSTEM CLOCK! If you see that your clock is losing time, document your system setup information and replace the battery as soon as possible. If you turn your computer on and off each day, you are more likely to experience an outage -- a weak battery may fail completely after you shut the system down.
I recommend that IBM compatible users print out their setup information, place it in an envelope and tape the envelope to the bottom of the case. This ensures that critical information, like hard drive specifications, is available when needed. Various software utilities perform the same function, but there is nothing less expensive and more sure than printing this information out and having it where you can find it.
If Your Clock Battery Fails
Newer computer systems can usually reboot using the default settings as long as the system hard disk has been detected by the BIOS. Older IBM and clone systems don't have this feature so the user is forced to enter the disk properties (heads (HDS), cylinders (CYL), sectors per track (SPT), write-precomp (WP) and landing zone (LZ) information into the CMOS setup screen so the BIOS can find the operating system. Newer systems us only the heads (HDS), cylinders (CYL) and sectors (SPT) information. CAUTION: ENTERING INCORRECT HARD DISK SPECIFICATIONS CAN RESULT IN LOSS OF DATA AND POTENTIALLY DAMAGE THE DRIVE!
Macintosh systems keep this information in a PRAM file that is stored on the disk. Typically, the only things that Macintosh users need to do to restart they system after replacing the PRAM battery is select the "Chooser" icon then set the screen type (color or black and white), the printer connection, the network connection information (if any), the date and the time. If the Macintosh doesn't start up correctly then the user may have to "zap" the PRAM to get the system running again. For complete information on this process visit http://docs.info.apple.com/article.html?artnum=2238.
Can I Replace The Clock Battery Myself?
The answer, in almost all cases, is an unqualified “YES.” Most clock batteries either snap into a specially-made receptacle (lithium coin cells) or can be easily unplugged (Rayovac 840, et al) from the system board. If the new battery is replacing a coin cell that is soldered to the system board a jumper must be changed to make the system recognize the new battery. Beyond that, it’s just a matter of restoring the system information, restarting the computer and going back to work.
Battery Do’s And Don’ts
NEVER attempt to solder wires directly to a coin cell! The battery may explode and spray toxic chemical paste into your eyes. If you replace a coin cell battery, don’t just throw the old one in the trash. Place the battery in an old 35mm film container or other enclosure and tape the lid shut. Coin cells are just the right size for a toddler to taste-test and are very dangerous if swallowed. Lithium brick and cylindrical cells should also be placed in a sealed container before disposal. Check your local regulations before you attempt to dispose of any quantity of this type of battery.
Alkaline cells may be disposed in landfills unless prohibited by local ordinance. This type of battery is the least harmful to the environment. Please remember NEVER to place any type of battery in an incinerator or dispose of by fire. It can explode and cause serious injury.
The increased use of personal uninterruptible power supply (UPS) systems has placed a large number of lead acid batteries into homes and businesses throughout the U.S. These batteries, in general, have a service life of 24-36 months. DO NOT place lead acid batteries in landfills! Please be responsible and take the battery to a recycling center. For more information on recycling visit http://www.call2recycle.org/.
What To Look For If You’re Buying A New Computer
Check the system out thoroughly! If the system board uses a coin cell battery, check to see if it's in a cup that provides for easy replacement and isn't soldered directly to the system board. If it is soldered, check to see if the manufacturer provided a connector for an “external” battery with an enabling jumper. If the coin cell can't be easily replaced or jumpered-out for use with an external wire-harness battery, look for another system board. Taking a system apart just to replace a coin cell battery can be VERY expensive. Using coin cells reduces production costs for manufacturers but can increase the cost of ownership to the buyer. Finding this out before you purchase can save you time and, perhaps, as much as a hundred dollars in unnecessary cost.
You can maximize your productivity by planning ahead to avoid this preventable failure. Take a few minutes to document your system setup and make computer clock battery replacement part of a systematic preventive maintenance program for your computer.
Barry A. Goldblatt is a consultant and nationally recognized authority on computer clock battery failure. His companies, Resource 800 and Epower2go, Inc. have been selling computer battery products by Rayovac, Tadiran, Dallas Semiconductor and other manufacturers online since 1992. Is Your Computer Clock Losing Time? was first published in 1992 and is known as the article that "started it all."
The author's writing credits include articles for newspapers, magazines and web sites throughout the U.S. including Technical Photography, Audio-Visual Communications, Computer Currents, Texas Computing, Home Office Computing, QST, P.A.R.K. (http://www.k5prk.org/), Ham-Com (http://www.hamcom.org/) and ARRL Online (http://www.arrl.org/).