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Compaq Portable III CMOS Battery

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cgrape2

Experienced Member
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Jun 11, 2009
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Lodi,CA
I'd like to replace the CMOS battery on my Compaq Portable III 386.
OK, here's the description:I think it is located near the top of the board, and ISN'T soldered in. It has a total of 4 pins, or "legs," and is inscribed: Lithium Battery-1.5AH-3.4V-Compaq Part#107157-001-Eagle Picher Ind (manufacturer?)-It appears to have two separate cells, plus the other electronic components that are located above the cells.
Am I right that this is it?
Could a replacement be cobbled together with common stuff?(Like with stuff from Radio Shack?)
I need some guidance here.(Stop me before I kill again!)

cgrape2
 
cgrape2 said:
I'd like to replace the CMOS battery on my Compaq Portable III 386.
OK, here's the description:I think it is located near the top of the board, and ISN'T soldered in. It has a total of 4 pins, or "legs," and is inscribed: Lithium Battery-1.5AH-3.4V-Compaq Part#107157-001-Eagle Picher Ind (manufacturer?)-It appears to have two separate cells, plus the other electronic components that are located above the cells.
Am I right that this is it?
Click to expand...
http://www.etiexpress.com/ProductAdv.aspx?pid=8806 indicates that part number 107157-001 is a battery for the Compaq Portable III

cgrape2 said:
Could a replacement be cobbled together with common stuff?(Like with stuff from Radio Shack?)
Click to expand...
Probably, but in constructing a replacement, be aware that there are discussions on the Internet about batteries and cells exploding when soldered. One suggestion to get around that problem is to use battery holders.
 
Yep,that's exactly what I had in mind.3.3V batteries seem hard to find(my local Radio Shack didn't seem to have any),but 3.6V batteries are fairly easy to locate.Would that voltage difference(0.3V)be a problem?
I think I can handle the fairly simple job of splicing wires to the old connection,so it's just this question I have now.
I also found the disassembly PDF pretty useful for the physical breakdown,Disassembly\reassembly.
Thanks for the reply.
cgrape2
 
I very much doubt that 0.3V will really blow anything up. But if you feel concerned, you could try backwards; 3.0V batteries are pretty common. I replaced a 286 laptop's 3.6V battery with a 3.0V battery and it holds settings just fine.
 
cgrape2 said:
Yep,that's exactly what I had in mind.3.3V batteries seem hard to find(my local Radio Shack didn't seem to have any),but 3.6V batteries are fairly easy to locate.Would that voltage difference(0.3V)be a problem?
I think I can handle the fairly simple job of splicing wires to the old connection,so it's just this question I have now.
Click to expand...
In comes down to the RTC/CMOS chip (could be part of a chip set) used in the computer. Chips such as the 146818 (used in the IBM 5170) and BQ3285 can handle up to 7 volts.

I don't think an increase of 0.3V is going to be an issue in this case. I think it would be very odd for a RTC/CMOS chip to handle 3.3V (or was that 3.4V) but not handle 3.6V (with 3.6V being as common as it is).

If you want to be 100% certain, we would need to identify the RTC/CMOS chip used in the computer then find its specifications.

Something to consider. The battery component of your 107157-001 module might be 3.6V but because of the "other electronic components" you write of, there could be a small voltage drop resulting in the module supplying 3.3V (or was that 3.4V).
 
You are correct that 3V batteries are cheap and common.Even a couple of AAA or AA batteries should work.I haven't dissected the old module yet,I'll report back when I do.Thanks youall for the help and insight!
cgrape2
 
cgrape2
How you decided this problem with batarrey? Because i have the same problem.
And i dont understand in this compaq portable III we have accumulator or battarey ???
 
I went with a battery holder and 2 AAA batteries.I soldered the old wire with the connector to the battery holder and it worked!
Accumulator? Could that be a Capacitor???
cgrape2
 
OK,now that seems to ba a real deal! So much better than a hacked together battery.Thanks for the info!!!
cgrape2
 
Hello,

I have the same error on my "new" Compaq Portable III. I've found a Dallas DS12887 battery, would this work? I know little about this computer, so I wish to know how to fix this! It was listed as working, but I can't do much unless I fix this.

Also, will I have to install an OS once I've put in the battery? Or will I have to run a diagnosic disk?


James B
 
Allied Electronics sells the original EaglePicher battery without the blocking diode and 1.6k resistor.

Original Compaq part number: 107157-001
Original EaglePicher part number: LTC-7PMP-F-S2 (no longer available unless you have very deep pockets)

Currently available EaglePicher part number: LTC-7PMP (You will have to add a series diode and resistor externally)
Allied part number: 710-5025

Enjoy
 
I'm now trying to do something with mine too. On the EaglePicher data sheet, it says * Battery contains diode and resistor protection (IN5817 diode, 1.6k resistor). So would it still be safe to wire up a different style battery without this protection?
LTC-7PMP-F-S2 Bottom.jpgLTC-7PMP-F-S2 Top.jpg
 
I need a new CMOS battery...

LTC-7P 3.5V 750 mAh Lithium (w/ PCB Termination) => this one is available now...
LTC-7PMP 3.5V 1500 mAh Lithium (w/ PCB Termination) => this has to be order 5 weeks lead time...

Does the mAh rating matter? Could I use the LTC-7P battery with my compaq portable III ? I do not have a spec sheet to tell me what the minimum mAh would be... seems like it would be that big of a deal since its just keeping the settings, clock?? right? hmm.

*Edit*
I just pulled the battery my part# 107157-001 printed on the black box... those batteries (there's 2 in there) are glued in there pretty good w/ the diode, resistor. I would like to reuse the black box, any tips in removing those batteries w/o damaging the black box? I am new to electronics... anyone have a drawing to show where to solder the diode(s) and resistor(s) in relation to the batteries...


Thanks in advance!
 
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raisedabar said:
LTC-7P 3.5V 750 mAh Lithium (w/ PCB Termination) => this one is available now...
LTC-7PMP 3.5V 1500 mAh Lithium (w/ PCB Termination) => this has to be order 5 weeks lead time...
Does the mAh rating matter? Could I use the LTC-7P battery with my compaq portable III ?
Click to expand...
In theory, the 1500 mAh one will last twice as long as the 750 mAh one.

raisedabar said:
anyone have a drawing to show where to solder the diode(s) and resistor(s) in relation to the batteries...
Click to expand...
For a guide, see the bottom half of the diagram [here].
Because the diode, resistor, and battery are in series, they can have any order. What is important is the polarity.
If there are multiple resistors, then they may be parallel to each other.
 
@modem7

Thanks for the diagram! I am a newbie to electronics and its terminology... but pictures speak a thousand words for me. I was going for the 750 mAh ones because they were suppose to be the same as the 1500 mAh w/ less mAh. But after they photos (which stated that they might not be the exact representation of the actual battery looks slightly wider than the original batteries which means they won't fit in the original black casing. Not sure if I could use it anyway it looks like they stuck the two batteries in there with the diode and resistor and then poured clear glue/resin/something... not sure if I can save the case... then blows. I wish I could solder a modern battery holder in there like the newer computers that take the coin batteries (i.e. CR2032) but the coins only have a mAh rating of 240. I guess its obvious I have no electronics background what so ever =)
 
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Revisiting this again. Just purchased a LTC-7PMP battery (w/ diode and resistor) this is the latest version of the original battery specs are the same... but we'll see when I get it. If its a match then I will order more... only thing is, the battery costs as much as what I paid for my whole computer =)
 
Hey James,
Its funny I saw reply and look at the dallas DS12887 battery and it looked like a rom chip, nothing like my battery (have several Compaq Portable IIIs), but recently, I purchased a cp3 and it had the dallas battery on it instead of the eagle picher brand. It was also on the right side of the motherboard instead of the center left like the others. Maybe there were a couple versions of the boards, I will have to investigate...
 
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