Armada E500 CMOS external pin.

It’s the time to replace the CMOS battery. Chanced to get a brand new one, are slim.
I want to install a 3.7V rechargeable battery.
The schematic is:

Comos + terminal < = - [T] – [1N4001 DIODE] – [ 10 Ohm resistor] <= +5V
....................................|
..................................---
.................................| B |
.................................| A |
.................................| T |
.................................| T |
.................................| E |
.................................| R |
.................................| Y |
................................. ---
...................................|
...............................GROUND
Could you please help, me with the location of external cmos connector on the motherboard?
Sorry for my English …

 

Hi Blue,

Your idea of a rechargeable battery is good but it is not worth the trouble. Use two Alkaline AA, AAA or similar cells. The circuit uses so little current that the batts will last as if they were not even being used. That is about 5 to 8 years if they are fresh when installed. They can be soldered to if you use a hot (about 30 watt) well tinned iron and do the job quickly. I use a little non-acid soldering paste to speed the job. If you need more info feel free to ask.

Good Luck, Jim

 

Hi Jim,
Thank you for your time, and for the good advice. You are right. I was over thinking, and forgot that Armada E500 with 900 MHZ processor, and 512MB of RAM after 3 to 4 years would be obsolete. I use this laptop as a soldier surfing on the Internet at non-secure web pages. Every 3 months I boot and Nuke the HD and re install windows XP Pro SP3. I don’t fight with viruses, I wipe out the HD.
For secure web pages I use a Toshiba 1.5 MHZ processor, and 1GB RAM.
For Skype, OOVOO and Photoshop I use another dual core 2.6MHZ and 4BG RAM, with the web cam incorporated, and of course with window 7.
Based on your advice I’m going to buy a CMOS battery with wiring and the connector for $3. Replace the old one. Solder two AAA in serial, connect with the old CMOS battery wires, and Re-plug to the CMOS connector. I have a 25W Thermostat controlled solder Iron, and Radio Shack soldering paste.
Thank you for very practical advice.
Sincerely,
bluerose.

 

Hi again Blue,

Test for a CMOS batt that is bad - The time and date goes way off everytime you remove power for several hours. The CMOS setup gets dropped later as the batt goes lower. Digital Voltmeter shows below about 2.8 Volts.

You shouldn't have to buy anything except the AA or AAA batts. Solder jumper between the two, solder 6 or 8" leads to batts. Solder the leads to the batt holder on the Mother board at bottom terminals of the holder. Check before you remove the old batt with voltmeter to find the correct polarity. Used to do this when old mbs came with 3.6 V nicad rechargeables using 3 AA batts plus diode to kill the recharge current.

Edit: That MB should have a coin shaped batt #2032 Lithium 3.0 Volt. You will see it in a holder flat on the MB or standing on edge. If you have a Radio Shack or similar store they will have the batt.

Good Luck,

Jim

 

Hi Jim,
Removed the switch cover, and located RTC battery near the power switch in vertical position.
Checked the computer for any +5V source. The easiest point vas the cooling Fan wiring. RED/BLUE. RED is +5V, but the BLUE resulted not a true ground. The millimeter indicated no pure connection with the ground. Not a surprise because the source of the fan is a temperature controlled power supply. The best source is the USB, but was hard to reach this point in my laptop.
There was no space to accommodate 2AA, or 2 AAA batteries inside the laptop. There is a place near the cooling fan for a thin 3.7V cell phone rechargeable battery. The function of silicon diode is to prevent the battery from discharging through the computer power supply when it is turned off. But there is one more important role. The diode creates a voltage drop of 0.6 Volt, so the battery can be charged at 4.4V max.
While this solution is very practical for a desktop (you can get very easy the +5V and true ground from USB port pins), it is hard for many LAP TOPS unless you tore apart all computer, which I do not deserve. So I gave up for this variant.
Bought a set of 2AA alkaline battery date of manufacturing May 2010. Connected in serial with an insulated wire from Radio shack, tinned the terminals and joined with 8” red and black wire accordingly with the polarity of the battery. Secured both batteries with electrical tape.
The existing CMOS Battery was a CR1620 MnO2-Li Cell. Two wires RED/BLACK was tinned in metal strips, which were spot-welded on the each side of the battery. The battery was covered with a clear cote-insulating envelope. The other side of wires ended in a two-wire connector creating a plug and play assembly. The voltage reading was 2.9 Volts.
Connecting the wires directly on the battery can result in overheating which can led in a bad battery.
If you search for CR1620 you’ll get a stripped CR1620, and you will take care for the rest.
If you search for ARMADA E500 CMOS battery you get everything preassembled ready to plug in the connector. Chanced to get a brand new preassembled battery are slim, but I hope they can last a least one year, which is more than enough for me.
I went for the option two. Till the order will be shipped I have connected 2 AA batteries, fixed from outside on the back of the computer with tape. This is a temporary, but very safe solution. As soon as I’ll get the Cmos battery, this will be installed inside the computer. As soon as the computer will change time again, then I will plug the 2AA battery with the connector that I already have, and will order new Cmos battery assembly. I hope this would happen no more than once per year!!
Thank you for the help.
Anything is possible, but is not worth to spend more of my time for an ARMADA E500 laptop.
Thank you again.
Sincerely,
Sam

 

Hi Sam,

I have to apologize. I was thinking desktop. Laptop is a completely different animal.

I have also replaced laptop CMOS batts. Batt with tabs are difficult to come by. I have used the same batt without tabs. Remove the old batt solder the old leads to the new one even more carefully. Wrap or heatshrink around the batt.

Rechargable batts for Desktops went out of style almost 20 yrs ago. Laptops about the same. If the old batt is not rechargable you do not need the diode if connected to the same place as the old CMOS batt. It will not do the job connected to just any +5 and ground. It must be connected to the CMOS/Time&Date circuit.

The Lithimum batts used today are good for up to about 10 years. It will let you know when it needs changing by dumping the time and date. This is probably true by design.

AA or AAA Alkaline batts ratings are many times that of the original batt. Any CMOS batt today is under practically no load and will last the same as if it was not even installed (on the shelf).

Hope I was a little help.

Thanks for the thanks.

Jim