Old AA battery sizes for test gear

[joeqsmith]

I have some very old UM-3(B) batteries.  These were made by Fuji Electrochemical Co, Tokyo Japan.  They are marked:
NOVEL
Top Run Black
100% Seal

While they look like a standard AA cell, they are roughly 49mm long.  Interesting, they never leaked.  The device they fit into will not take a standard AA cell without doing a little adjustment with a hammer (on the cells).   

Are there still 49mm UM-3 cells available? 

[BMack]

What does the battery holder look like? Maybe a solder-in cell would work since they don't have a nipple.

[Ian.M]

Hack an AAA to AA adapter sleeve?

[amyk]

Perhaps the battery compartment has shrunk slightly? This is not uncommon if it was made of plastic.

[Cyberdragon]

Perhaps telling us of the device will help determine if it needs special batteries. I've never heard of simple letter type batteries having changes in size, so it might be damage to the battery holder. If it's one of those spring types, just cut a few coils off the spring to get more space.

[joeqsmith]

Hack an AAA to AA adapter sleeve?

This is what I am thinking.  I see a few advantages to going this way.   

It looks like Panasonic still makes some of the shorter cells but they are not very common.

[joeqsmith]

Left is the original battery that I believe was supplied with the unit.   

[joeqsmith]

Machined up a couple of cases.   The original batteries have a plastic sleeve that went over the cell.  Then the metal band at the bottom is crimped to seal it up.   I cut the band with a razor blade then slit the cover to remove it.   I plan to just let the spring keep the battery in-place.   

Amazed that after so many years, nothing leaked from the cell.   Time to reverse engineer this thing.

[Ian.M]

Result! 

That's also good insurance against future leakage as the seal on modern AA and AAA Alkalines is also at the negative end.  Put a thin smear of dialectic grease on the jacket of the AAA before inserting it in the sleeve and any leakage should be contained in the sleeve.

[Cyberdragon]

Just keep in mind you will have to change the batteries more often when using a lower capacity battery.

[joeqsmith]

Result! 

That's also good insurance against future leakage as the seal on modern AA and AAA Alkalines is also at the negative end.  Put a thin smear of dialectic grease on the jacket of the AAA before inserting it in the sleeve and any leakage should be contained in the sleeve.

Yes, this is one of the advantages I mentioned.  The sleeves are not yet finished (a bit more machining to do) and I had considered adding an inside ring groove to trap it and use a Buna N seal.  I'll post some pictures what it looks like once I have them all done.   

[SeanB]

Might also machine the sleeve to be oversize internally, and use a thin extra insulator, just in case the cell sleeve is conductive, no need to make a impromptu electric gun if the alkaline cell shorts out. Another idea is to use a cutter that shapes the negative contact inside to be a dome shape, so there is less chance of shorting, or just make a pip on the outside and sleeve the whole item as a positive side use item, so that you need no inner insulation for a typical AAA alkaline cell, which typically uses a negative end seal.

[joeqsmith]

Pulled the second battery apart.  It was a rough as the first but no signs of any leaks.   Soldered the two end caps back together and finished up the two sleeves.  There was not enough meat left to install the O-ring. 

[joeqsmith]

Glued the old jackets to the custom sleeves and installed the end caps and springs.  I plan to just rotate the seams so they don't show.  All the trapped corrosion caused the jackets to get a little lumpy.   I installed a couple of AAAs and used my just slightly chopped up YX-360 to model them.  Gives that Chinese meter the early 70's Japanese look.   

Battery problem solved, time to get back to sanding Bakelite.

[grifftech]

harbor freight batteries are shorter than most

[joeqsmith]

I bought some from them marked Thunderbolt Magnum Alkaline.  These are within 0.005" of the Duracells I looked at.  Your store must carry a some other brand.  Post the brand you bought from them and measure the length of a few.