Battery for a vintage VOM

[Bi11Hudson]

Battery "form factors" have been wild until relatively recently. They come from early builders of vacuum tube radios. And model airplane builders. And any number of specialty applications. The recent "standardization" is a God send to me. Recent being since 1967 or so. In those days, odd voltages were profligate, and that on a good day.

The point I came onboard to make has to do with a, I think Triplett, multimeter that dates back to a friend's father working in the shipyards in the '40s. It uses a solid "brick" rated at 4.5 volts for the resistance scale. I replaced that with a "D" cell carrier with three cells. It works fine now, has for twenty years or better.

Also have a fiber optics "OTDR", basically an archaic XT with a ram disk. Hard disks in those days were pretty big, 13 inches or so deep. It also has a three cell keep alive battery, that gets changed whenever I happen to think about it.

Dry cells, carbon-zinc cells, have been around since the git-go of radio. Even the current 9 volt transistor battery is 6 each 1.5 volt dry cells bonded together inside the can. You just made a larger version. Keep up the thinking.

.

 

[whitmore]

Well, ya see, I've had this-here vintage Hewlett-Packard 427A volt-ohmmeter for quite some time.
View attachment 301419

Had it stored away for a few years, finally unearthed it a couple weeks ago. Unfortunately, the battery (an Eveready 763, 22.5 volts) had died of old age (originally installed in 1999)....
So what to do? AHA!!! I did a bit of figgering and tried dividing 22.5 by 1.5. Got 15. Stacked up 15 AA cells, and ...[Success! ]

A possibly easier route would be to divide 22..5 by 3.6; six lithium cells would work, and
they're available pre-wired for easy connection <https://www.digikey.com/product-detail/en/tadiran-batteries/TL-4902-P/439-1060-ND/1949333>

 

[Downunder Bob]

Always a new way to stick the pig or skin the cat. Eneloop batteries are my fave, you could always make a holder out of plastic tubing so they don't have to be soldered that way easy to take apart and recharge,.

 

[markba633csi]

I have/had a boy's book about electrical projects you could build. One of the last ones was a Geiger counter. Parts list:
1- 300 volt Geiger tube
3-300 volt batteries
1- pair of headphones
1- capacitor
1-resistor
Sounds real safe doesn't it? As if you can just pick up this stuff at Radio Shack-- Book was written in the 50s
Mark

 

[Superburban]

After messing up a VOM, by having the batteries, I have been only using the ultimate lithium, AA, and AAA batteries. They do not cost that much extra, but do claim to last longer, and that they will never leak. I did a similar thing, using 3AA batteries in a holder, to replace a BA-31 4.5 volt battery. Actually 3 holders, and 9 batteries, as the meter takes 3 BA-31's. Here is a pic of the BA-31's, the 3AA holders are about3/4'a the size of the BA-31. The missing battery, is a BA-30, or standard D cell. I would like to find some lithium D cells.

 

[hman]

Thanks to all of you for your responses!

nice save hman!
i like the other way of skinnin' cats when the alternative is ridiculously expensive.
i wasgunna' suggest using a 115vac transformer with a 24vac secondary.
if you add a bridge rectifier, the result would be a right about 22vdc
if you ever wanted to go that route

Thanks! I didn't really consider a homebrew 115VAC power supply ... mainly because I'd have to work really hard at suppressing ripple. I suppose I could have "adjusted" a commercial 24VDC supply to output 22.5, maybe even run the meter with 24. But the battery substitution worked well, with little extra effort.

Battery "form factors" have been wild until relatively recently. They come from early builders of vacuum tube radios. And model airplane builders. And any number of specialty applications. The recent "standardization" is a God send to me. Recent being since 1967 or so. In those days, odd voltages were profligate, and that on a good day.

The point I came onboard to make has to do with a, I think Triplett, multimeter that dates back to a friend's father working in the shipyards in the '40s. It uses a solid "brick" rated at 4.5 volts for the resistance scale. I replaced that with a "D" cell carrier with three cells. It works fine now, has for twenty years or better.

Also have a fiber optics "OTDR", basically an archaic XT with a ram disk. Hard disks in those days were pretty big, 13 inches or so deep. It also has a three cell keep alive battery, that gets changed whenever I happen to think about it.

Dry cells, carbon-zinc cells, have been around since the git-go of radio. Even the current 9 volt transistor battery is 6 each 1.5 volt dry cells bonded together inside the can. You just made a larger version. Keep up the thinking.

Durn! I'd forgotten all about those 9 volt batteries when I was describing the innards of the 22.5V. I guess the 9V is the last stacked-cell "dinosaur" still in existence. Good save on the 4.5V battery!

A possibly easier route would be to divide 22..5 by 3.6; six lithium cells would work, and
they're available pre-wired for easy connection <https://www.digikey.com/product-detail/en/tadiran-batteries/TL-4902-P/439-1060-ND/1949333>

Hmmmm ... wasn't aware of that size cell. 1.2Ah is pretty good, too. Cost would have been a bit higher than the AA alkalines, but wiring would definitely have been easier. Thanks for the link!

Always a new way to stick the pig or skin the cat. Eneloop batteries are my fave, you could always make a holder out of plastic tubing so they don't have to be soldered that way easy to take apart and recharge,.

As I'd mentioned in my post, I like the Eneloops, too. Unfortunately, I couldn't think of a way to make a 15 cell holder that wouldn't have taken up far too much space.

I have/had a boy's book about electrical projects you could build. One of the last ones was a Geiger counter. Parts list:
1- 300 volt Geiger tube
3-300 volt batteries
1- pair of headphones
1- capacitor
1-resistor
Sounds real safe doesn't it? As if you can just pick up this stuff at Radio Shack-- Book was written in the 50s
Mark

OUCH!

After messing up a VOM, by having the batteries, I have been only using the ultimate lithium, AA, and AAA batteries. They do not cost that much extra, but do claim to last longer, and that they will never leak. I did a similar thing, using 3AA batteries in a holder, to replace a BA-31 4.5 volt battery. Actually 3 holders, and 9 batteries, as the meter takes 3 BA-31's. Here is a pic of the BA-31's, the 3AA holders are about3/4'a the size of the BA-31. The missing battery, is a BA-30, or standard D cell. I would like to find some lithium D cells.

Another nice save! Yup, it would be nice if there were a lithium D cell ... my best guess is that D cells are not popular enough any more to justify the R&D and manufacturing investment. Think of how few devices are sold any more that use Ds. Shucks ... they may soon be on the path to extinction

 

[Superburban]

Another nice save! Yup, it would be nice if there were a lithium D cell ... my best guess is that D cells are not popular enough any more to justify the R&D and manufacturing investment. Think of how few devices are sold any more that use Ds. Shucks ... they may soon be on the path to extinction

Did not think of this until reading your post. Somewhere I saw D & C cell shells that you put a AA battery into. Will have to look, maybe it was Ebay, or amazon.

 

[hman]

Yeee-haaaa! I recall seeing that kind of thing years and years ago, back before AA cells went alkaline and had miniscule capacity. Kinda reminded me of a [insert your favorite stereotype]'s bankroll ... a thick roll of one dollar bills, with a 20 wrapped around the outside for "flash."

Given the very light weight of the Exell battery I got, I was wondering if they'd done something similar with it. But I didn't want to take it apart and look. It would have made the thing un-returnable. Gotta wonder, though ...

 

[Superburban]

Given the very light weight of the Exell battery I got, I was wondering if they'd done something similar with it. But I didn't want to take it apart and look. It would have made the thing un-returnable. Gotta wonder, though ...

If not AA's, it has some sort of readily available battery inside, I would bet on it. Since I have a good size collection of multimeters, I have gotten so I put a label with a date on the ones I install batteries in. Most of them you can still use for measuring voltage without batteries.

 

[RJSakowski]

The analog VOM's only used a battery for measuring resistance. My Triplett VOM uses a D cell for the lower resistance3 scales and the 30 volt battery is only used on the R x 100K scale.

Back in the days when you still had to set dwell on a distributor, I would use my VOM. I could chuck the distributor in the lathe and connect the VOM resistance leads across the points. The meter was set on a resistance scale and the lathe turned on. The fraction of a full scale reading x 360/ no. of cylinders is the dwell. For example for V8 engine, a 6 volt reading on the 10 volt scale would be 6/10X360/8 or a dwell of 27º.