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PCB battery replacement - determining type

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spiffitz

New Member
This is a Computrac moisture analyzer. It gives me an SRAM error and it goes away if I reset the board via built-in reset switch (seen in the background), but it errors again when powered-up the next time. The batteries are corroded and have no voltage left. How do I tell what I need - can anyone tell me if these are Nicad, lithium, etc? They measure 1.10" (28mm) long and .55" (14mm) diameter. Are these N-size? If they're basic 1.2v N cells I'll just solder in a double-N holder. But what if the board is supposed to recharge them?


The company is useless. Once I mentioned it being an old out-of-warranty product they basically ignored my emails from then on.
 

Sceadwian

Banned
Toss the residue up on an Xray. =)
Probably NIMH.
 
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Draco

New Member
To me they look like nicad batteries, old ones are known to corrode like mad, they also look like they are in series so i would replace them with nicad or the hydride versions we love today. The board most likely does recharge them so i would only use rechargeble cells
 

spiffitz

New Member
Thanks 3v0 but I've already gone that route. They won't help me unless I mail it in for their $500 calibration fee. They wouldn't even tell me what the error code on the display stood for. I had three different contacts there (I know what they look like - their pics are on the site) and they all mysteriously stopped responding to my emails after I send them the serial #, which they will not correspond without.

I'm just hoping someone recognizes those batteries.
 

3v0

Coop Build Coordinator
Forum Supporter
Just thinking.

You can check what voltage is present at the battery terminals with the unit on. If they were charged by the board you should see a voltage. If not charged by the board I doubt that you will see a voltage due to the dioed used to keep current from flowing into the batteries.

If this is like or one of the devices listed in their FAQ they are rechargable.
The Computrac® MAX® 500, 1000, and 2000 series instruments and the CT-3000 have internal batteries that maintain power to the memory during times the instruments are switched off, or in the case of a mains power failure. ...
These instruments should not be left unplugged for weeks at a time, since the batteries could run down, resulting in the loss of stored calibration parameters and memory start information. These batteries are replaced by the factory when the instruments are sent in for annual calibration.
When I read between the lines I see rechargable batteries.
 

mneary

New Member
You can tell they are NiCd by their age and the characteristic color/texture of the junk they emitted. I've never seen exactly that same stuff from a NiMH. Since there are no telltale dimples in the shrink wrap between cells, you have two 1.2V N-cells. You can confirm this by measuring the voltage that the circuit attempts to charge them with (should total about 3V), and further by splitting the blue plastic with a knife.

Suitable replacements are similarly sized NiCd or NiMH.

Unfortunately replacing the batteries and resetting the board won't get the calibration parameters back.

If you live near me, give me a shout; I have some n-sized NiCds I have no use for.
 

spiffitz

New Member
OK I will test for voltage at the terminals with the batteries out. That's the other tricky part, the solder is pretty hard and my 30-watt iron isn't budging it.

What about battery voltages? They can't be anything other than 1.2v cells, can they? I'm thinking of putting a connector in there and use easily obtained 2.4v cordless phone battery packs.

edit - thanks for the offer mneary but I won't be in socal until next month :) The calibration and other saved parameters will have to be up to the person who purchases this. They're already getting it at a major discount.
 
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3v0

Coop Build Coordinator
Forum Supporter
Maybe it is time to take a step back.

If you modify this unit the company that built it may well refuse to calibrate it. Even if you get it fixed the unit will be junk.

Their web page indicates they replace the batteries when they do calibration. Is it possible to have the board repaired anc calibrated prior to sale.

Or sell it as is. With a clear indication of the condition.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
As others have said, they are NICAD's, and that is exactly what NICAD's do - often corroding the board beyond repair as well.

Also as others have said, replacing the batteries won't cure the problem, as they are for maintaining data in static RAM - which will now be blank.
 

MrAl

Well-Known Member
Most Helpful Member
Hello,


I think they are NiCd's too, because that is the type of cell normally used
in equipment where the cells are 'built in'. They dont usually use NiMH
because of the higher cost of the charge circuit, and NiMH are not as
good for charging while the circuit is running while NiCd's are very typically
used exactly in that way.

Another fact that is interesting here too:
Since NiMH have a more rigorous charge regime than NiCd's, it is almost always
possible to replace NiMH with NiCd, but not the other way around. The worst
case is that the capacity will be a bit less with NiCd than NiMH, but at least
it will work for another 5 to 10 years if the charge circuit is ok.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
It gives you the feeling these people wanted to keep you sending the systems in each year. Had they used EEPROM or flash it would not have been a problem.
That's perhaps a little cynical :D

It's simply from the era where that's how things were done, it took a long time for EEPROM (it was way before 'flash') to gradually take over from the normal battery backup.
 

3v0

Coop Build Coordinator
Forum Supporter
I would agree but that it seems they are still using the same business model. The are selling the 2000XL and their text indicates it uses batteries. See quote in post #6. I would rather be wrong on this one.

That's perhaps a little cynical :D

It's simply from the era where that's how things were done, it took a long time for EEPROM (it was way before 'flash') to gradually take over from the normal battery backup.
 

spiffitz

New Member
Update and new question

I'm searching for a battery ID thread and found this one, which I completely forgot about, so I guess I'll drop an update.

I gave the unit back to him, and he decided to go ahead and do the service fee of $xhundred then got it back. When he did get it back, the unit still did not work right and they told him that there was another calibration that the factory "forgot" and had to charge him for that again. What a scam. At least he made some money off of it when he finally did sell it.

So now for my next question. I have this:


I mistakenly thought (as the cells were dead) that it was a basic double-cell 2.4v pack so I bought new cells. Turns out there's a little surprise inside the shrink wrap. There is no room in the unit to put any other 5v pack; what you see is all it has room for. All my battery sources don't seem to list this size, which as you can see is about 15mm long and wide. The company wants $45 per pack:eek: and I need four. They need to be NiCad because it includes the base and charger. Any clues would be appreciated.
 

Sceadwian

Banned
Looks like a 1/3 N sized cell.
You can get them out of some minature RC cars like zipzaps or generic equivilant.
 

Sceadwian

Banned
Sorry spiffitz, you are mistaken. 1/3N is a package size it has nothing to do with the voltage. Cell chemistry and series configuration determines the voltage.

The reason I can be so sure you are mistaken is that I actually have at least two NiCads of that size.
 
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