Site Search

Site Info

Home » Forums » Forum Archives » Other Computer Problems » Topic # 509

od 486DX2 PC not booting
bernard delr Jul-25-02 00:54 AM
i received a "cmos battery low" message during bootup, after shutting down it won't boot again. i get a blank screen but power indicator is on. i hear beeps... help! please....

1. RE: old 486DX2 PC not booting
Twinhead Jul-25-02 06:11 AM
In response to message 0
LAST EDITED ON Jul-26-02 AT 01:51 PM (EDT) by lbyard (admin)
Your CMOS battery is most commonly one of a rechargable type.
Open the case, and see if there is a blue or grey "rugged" plastic foiled cylinder on your mainboard.
It consist of three NiCd buttoncells in a crimp-foil.
Mostly near your keyboard or power connector.
Newer 80486 Mainboards have a Lithium cell.
This is a CR2032.
A coin shaped silver colored cell with CR2032, 3V and a + on one of its sides.
That is easy to exchange since they are clicked in a plastic base.

If in case of the older type, and there is a white-grey powder-like material on the metallic sides, the battery is history.
If no powder-like material, switch on and leave on for at least 12 hours in attempt to recharge it. (Disconnect the loudspeaker if annoying)

In case of dead / history battery:
If you are capable of handling a small soldering iron, and have built computers already, you can disassemble the pc, take out the mainboard, desolder that battery and get a new one.

Do not do this with lithium batteries! Never, NEVER apply heat to or near a lithium battery!!! They can explode!!! See http://duxcw.com/faq/cmos/cmos.htm. Larry


Most common fetchable by electronics shop and Telephone shops.
They are similar to rechargable batteries in the handset of many cordless phones.
See for a 3,6V type with as much as MAh possible (Should also be fitting in the original place!)
You can do the next if not fetchable:

Take three AAA rechargable batteries, solder the + and - together like this schematic:

Wire#1 to +Batt#1- to +Batt#2- to +batt#3- to Wire#2

Insulate the whole thing well.
Solder the other end of Wire#1 to the + pole on the Mainboard.
Solder the other end of Wire#2 to the - pole on the Mainboard.
Reassemble the PC.
switch on and leave on for at least 12 hours to recharge it. (Disconnect the loudspeaker if annoying)

After this, you have to reset the parameters to your CMOS and you can use it again.

2. RE: old 486DX2 PC not booting
bernard delr Jul-26-02 01:41 AM
In response to message 1
thank you so much!... it's a great help... i'll start working on it.. thanks again...

3. RE: old 486DX2 PC not booting
lbyard Jul-26-02 01:09 PM
In response to message 2
Never, NEVER apply heat to or near a lithium battery!!! They can explode!!! See http://duxcw.com/faq/cmos/cmos.htm. Larry

5. RE: old 486DX2 PC not booting
lbyard Jul-26-02 01:58 PM
In response to message 3
The following is quote IN PART from Panasonic’s OEM web site (http://www.mbi.panasonic.co.jp/oembatteries/english/e_ion/out_eion/atteion.htm). I strongly suggest going to the web site and reading the rest of it before handling lithium batteries. Larry

“Misuse of the battery may result in the battery generating heat, exploding or igniting. Be sure to observe the following safety rules.
* Do not dispose in fire or heat.
* Do not immerse the battery in water or sea water or allow it to get wet.
* Do not use the battery with the positive and negative terminals reversed.
* Do not connect the positive terminal and the negative terminal of the battery to each other with any metal object (such as wire). Do not store the battery with metal objects such as necklaces or hairpins.
* Do not pierce the battery with nails, strike the battery with a hammer, step on the battery, or subject it to other strong shocks.
* Do not directly solder the battery.
* Do not disassemble or modify the battery. The battery contains safety devices, which if damaged, may cause the battery to generate heat, explode or ignite.
* Do not place the battery in or near fires, stoves or other high-temperature locations. Do not place the battery in direct sunlight.
* Do not use or store the battery inside cars during hot weather. Doing so may cause the battery to generate heat, explode or ignite. Using the battery in this manner may also result in deterioration in performance and service life.”

8. Replacing Old Motherboard Lithium CMOS Batteries
lbyard Jul-26-02 02:57 PM
In response to message 5
A few years ago when a lithium battery (most of them are blue cylinders) that was soldered to the mother failed, we would very carefully remove it with pair of pliers and diagonal cutters. If left on the motherboard, it will most likely leak. When it leeks it can permanently damage the motherboard. The ooze will actually eat the copper traces on the board. Usually, motherboards with these batteries have a connector for an external battery. External lithium batteries than will plug into the connector are readily available. They do not have to be 3.6 volts. Most are 4.5 volts. Many are have a four-pin connector to match the header on the motherboard, but one or two of the middle sockets may be filled in to key the plug to the correct polarity (don’t count on it; trace-out the battery to the plug. Also, motherboard books are often wrong about which pin does what/is which polarity—must be a language translation problem) and many of the headers have all four pins or three of them. The workaround is to bend over the pins that are in the way. In many cases the same header is used to discharge the CMOS memory and it probably does have a jumper on it, which will have to be removed. The header and battery are often near the keyboard connector on AT/Baby AT motherboards. Be sure to record the CMOS setup info before removing a battery. The parameters (heads, cylinders, etc.) for old drives were often entered into the CMOS. Old drives often used compensation settings as well. And some old computers have odd (sometimes tricky) memory settings that are not seen anymore.

Another solution is to get a four-cell AA cell battery holder with the four-pin plug. These holders are or were readily available. I still have some in stock. They have adhesive on the back and were commonly stuck onto the side of the power supply. In fact, in the old days these battery holders were what was used for the motherboard CMOS in many computers. Four ordinary AA penlight batteries were used and will usually keep the CMOS charged for a couple of years or more. I have soldered a few these to the motherboards that did not have a header. One has to determine the Plus and Ground traces and find a convenient place to attach the battery holder wires (after cutting-off the plug). Of course, remove the lithium battery first as described above (never attempt to desolder it or get a soldering iron anywhere near it). You may be able to attach the leads where the old battery was mounted. A soldering iron can quickly melt the traces on a motherboard so be extremely careful. I used an Unger 25 watt (I think) Princess iron with a conical tip, which I bought many years. Weller bought Ungar some time ago. Larry

18. RE: Replacing Old Motherboard Lithium CMOS Batteries
lbyard Jul-27-02 01:20 AM
In response to message 8
After doing some more research it appears that those blue batteries, or at least some of those blue batteries, were Nickel-Cadmium and they were rechargable. The following references are worth a bookmark if you are interested in the subject. Larry


20. Ni-Ca ("Blue" CMOS Batteries) and Ni-Cd Battery Hazard
lbyard Jul-27-02 01:39 AM
In response to message 18
And according to Panasonic a manufacturer of these batteries (not necessarily the maker of the blue ones), they can explode also and the chemicals they use can cause blindness.


“Improper handling may result in battery short circuits, melted insulation, or damage to safety valves and mechanisms, causing batteries to leak, generate heat or rupture. Be sure to observe the following precautions for use.
* Do not heat or directly expose batteries to fire.
* Do not insert batteries with the anode (+) and cathode (-) ends reversed.
* The (+)(-) alignment of these batteries is determined. If batteries cannot be properly inserted into chargers or equipment, do not try to forcibly insert the batteries, but instead check the (+)(-) alignment.
* Do not directly connect batteries to electric sockets or automobile cigarette lighter sockets.
* Do not connect the anode (+) and cathode (-) of a battery with metal such as wire. Also, do not carry or store batteries together with necklaces or other metallic objects.
* Do not disassemble or modify batteries.
* Do not directly apply solder to batteries.
* When charging the batteries, be sure to use the designed Panasonic charger or to observe the charging conditions specified by Panasonic.
* These batteries have a gas venting structure for releasing internal gas. Therefore, do not deform the anode (+) portion.
When designing battery compartments inside equipment, avoid using sealed structures. These batteries may generate gas on occasion which may cause the structure to rupture or explode if the gas ignites.
These batteries contain an alkali fluid which may cause loss of eyesight if it enters your eyes. In these cases, do not rub your eyes, but instead wash them thoroughly with clean water, and immediately seek the care of a physician.”

I might turn all of this stuff into an article for future reference.


9. RE: old 486DX2 PC not booting
Twinhead Jul-26-02 03:36 PM
In response to message 3
Larry, Did i tel something wrong or did I miss something??

This is the first time that you have inserted a message inside my reply.


11. RE: old 486DX2 PC not booting
lbyard Jul-26-02 03:43 PM
In response to message 9
Victor, It might be a language problem. I had to make sure no one applies heat to lithium battery. It is a safety hazard. I am not sure that is what you meant, but that is the way it could be understood. As it appears on my web site, I had to be sure readers know that applying heat to a lithium battery can cause an explosion. I had to put that information where I did so they would be sure to see it. Best regards. Larry

12. RE: old 486DX2 PC not booting
Twinhead Jul-26-02 04:01 PM
In response to message 3
LAST EDITED ON Jul-26-02 AT 04:03 PM (EDT)
Hello Larry. (OOPS... It crossed your reply!)

Yet another word for Lithium:

This is not an attack on you, but information to the owner of the URL, AND the readers of this forum.

I see in the URL that the owner of the text does not use the word Lithium correct!

Any attempt to recharge a Lithium battery will couse it to explode.

The newest generation rechargables are of the type Lithium-Ion.
But, in the days of building the 80406 Mainboards, Lithium-Ion did not exist yet. (Even Nickel Metal Hydryde (NiMh) was not yet commercial)

The next is known to exist by me:

1 NiCd, Nickel Cadmium, Ordenairy rechargable battery with the possebility of the "Memory effect"

2 NiMh, Nickel Metal Hydryde, The better type rechargable battery who has allmost no memory effect.

3 LiIon, Lithium-Ion, The newest in rechargable batteries, Much capacety relative to its volume.

4 Lithium, the normal NOT rechargable battery (Mostly a CR2032 for newer Mainboards).


13. RE: old 486DX2 PC not booting
lbyard Jul-26-02 06:18 PM
In response to message 12
Victor, you are correct about lithium ion versus lithium batteries. There appears to some confusion all over the Internet on lithium and lithium Ion. I believe I will leave that warning in place, however, as those batteries are used in notebook computers, and, it appears that much of it applies to lithium batteries in general.

I was referring to the Lithium batteries soldered on the motherboard and used for CMOS a few years ago. I am no battery expert and do not plan to experiment with them, but I can tell you back in the days of the 286, 386, and 486 motherboards, and before, one was instructed not to get a soldering iron anywhere near lithium batteries as they can explode.

The following appears to apply to the motherboard batteries:


"The lithium-thionyl chloride batteries described in this Material Safety Data Sheet are sealed units which are not hazardous when used according to the recommendations of the manufacturer.

Under normal conditions of use, the electrode materials and liquid electrolyte they contain are non-reactive provided the battery integrity is maintained and seals remain intact. Risk of exposure only in case of abuse (mechanical, thermal, electrical) which leads to the activation of safety valves and/or the rupture of the battery containers. Electrolyte leakage, electrode materials reaction with moisture/water or battery vent/explosion/fire may follow, depending upon the circumstances."

There are several chemical variations of lithium batteries. Here’s an Eveready warning for Energizer Batteries (Lithium-Manganese Dioxide and Lithium-Iron Disulfide):


Here’s what the U.S. Navy says about Lithium batteries(http://www.safetycenter.navy.mil/afloat/surface/downloads/combatsystems.doc):

“Lithium batteries or cells are potential hazards if misused, tampered with before, during or after discharge. Lithium batteries have exploded while rapidly discharging and up to 30 minutes after discharge. Whether fresh or discharged, lithium batteries SHALL NOT be pierced, crushed, burned, intentionally dropped, cannibalized, dismantled, modified or otherwise carelessly handled nor shall they be short circuited, charged, or used in any other equipment then specified.”

I’m sure some of that sunk into my rather thick head during the 24 years I spent in the Navy.

I have soldered wires to ordinary flash light batteries (as difficult as it is to do). I will continue to keep my soldering iron well away from all others and would suggest that the warning for Lithium Ion batteries would be sensible warning for all Lithium batteries, and perhaps all batteries having unknown consequences when heat is applied. Larry

17. RE: old 486DX2 PC not booting
lbyard Jul-26-02 06:49 PM
In response to message 13
Actually, a CR2032 is a cell. And it may not be Lithium. But it is the correct "battery" for recent motherboards. A battery is a collection of cells (more than one cell) that are usually connected in series for greater voltage. Or, at least that was what I was taught in EE101 40 years ago. And, by the way, electrical current travels from the positive to the negative terminal. That statement will probably get a response. Larry

19. RE: old 486DX2 PC not booting
DJ Net2Infinity Jul-27-02 01:26 AM
In response to message 17
I was taught and truly believe that current flows negative to positive do to the charge of the subatomic particles, but it doesnt matter as long as you use the same convention.

| Home | Guides | How to | Reviews | Online Store | FAQ | Forums | Forum Archives |
| Links | News | Newsletter | About Dux | Advertising | Contact Info | Privacy |