AA & UM-3 Battery Length - Differences from brand to brand?

[Dave]

Hi All,

I have an older hardwired Audio Technica Pro 7A LAV that I was hoping to use for occasional public speaking gigs ; in emergencies when wireless is a problem.

It runs with a hard-wired single AA battery pack. My issue is that AA batteries are no longer fitting into the battery compartment - the battery (brand new Duracell) is too long and therefore too tight to get into the receptacle. I'm afraid to force it in and cause damage. I could swear that when I first got the mic a AA would fit without any issues. Have they started making these current AA's a bit longer?

Inside the compartment it indicates a "UM-3" battery, a Japanese AA equivalent? Maybe there's a slight difference in the dimension/length?

Thanks for any tips - much appreciated.

Have a great day!

Cheers,

Dave

[Eric Toline]

A UM-3 is 13.9mm in diameter and 50mm long as are all AA batterys. Could be that the flex contacts are a bit stiff and not flexing as they did. Push the battery in and the contacts will give a bit. Also make sure there's no gunk under the contact plate that's stopping the contact from flexing.

Eric

[Rick Reineke]

Don't know about the AT compartment, but on most, the negative (flat end) goes in first, then compress the spring or contacts to side in the + end.

[manwithamoviecamera]

I have the same issue with an approx. 50-year-old Japanese photographic slide viewer that I bought today, Dave, and which also was designed to take (a pair of) UM-3 batteries. According to Wikipedia, "An AA cell measures 49.2–50.5 mm (1.94–1.99 in) in length, including the button terminal—and 13.5–14.5 mm (0.53–0.57 in) in diameter." My guess is that such batteries were originally manufactured to be nearer the 49.2 mm end of said size range, and over the years have grown such that a new "AA" battery is closer to the 50.5 mm end? (Think I'll try filing half a mm off of the positive terminal! Worse, I also have old equipment that takes four AA batteries, in which some modern, high capacity, rechargeable are slightly too fat to fit!) 

[Matthew Steel]

I find that Lectrosonics HHa are a bit picky about AA batteries too.  The Duracells they ship with fit easily.  The rechargeables we usually use, on the other hand, are hard to get in.  A closer inspection reveals that while both cells are the same length and diameter, the Duracells have a narrower negative contact than the rechargeables.  That makes the rechargeables a bit to harder to tilt in.  They fit, but I have to use more force than I'd prefer.