# Battery for a vintage VOM



## hman (Sep 3, 2019)

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



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 I went searching.  Several sellers on Amazon and eBay must have thought the battery chemistry was platinum-iridium or something, judging by the prices they wanted.  Among the lowest prices was one on eBay for a bit under $70 ... sold by Lowes, of all places.  Gritted my teeth and placed the order.  

When the "Exell" battery arrived, I was taken aback by the weight - about half that of the old Eveready!  How could such a lightweight have anywhere near the milliamp hours capacity of the original?


It seemed far from right.  I didn't even try connecting it ... figured it would be easier to return if still in the original shrink wrap.  Luckily, the local Lowes store was willing to handle the return.

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 found they would easily fit within the same volume as the 763 battery.  Luckily, I'd not discarded the old 763.  Cut open the cardboard "wrapper" and removed the cell stacks - three parallel stacks of 15 chicklet-sized cells.


I soldered the AA cells together in series, wrapped them with electrical tape, re-connected and re-sealed them in the original battery wrapper, and checked the voltage - right on.





Loaded the "refurbished" battery in the meter, and by golly, it's happy!


I now have a very good mirrored scale analog meter.  True, even with the mirrored scale it doesn't give as many decimals of precision as a digital meter.  But nothing beats an analog meter for time-varying signals!  Furthermore, I have a nice, inexpensive source of replacement batteries!  Assuming 50¢ a cell, that's just $7.50 ... instead of $70.00 for a "new" battery!


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## matthewsx (Sep 3, 2019)

Nice, make the next one out of rechargeable batteries and you'll never have to worry about it again  

John


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## markba633csi (Sep 3, 2019)

Nice save John- I wonder why HP didn't just provide a 15-cell holder- Maybe some sort of sweetheart deal with Eveready?


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## RJSakowski (Sep 3, 2019)

I had a similar experience with a Triplett VOM that I acquired recently.  The battery for the high resistance scale was still available at but great cost.  The battery was a NEDA 210, 30 volts, 180 mah,  and 16 x 26 x 65mm. 

We have several appliances that use CR2032 lithium batteries that crap out when the voltage drops to about 2.8 volts.  I made a carrier from a piece of PVC tubing and loaded it with a dozen used CR2032 batteries.  Some button contacts on the ends and I had a 30 volt battery at essentially no cost.  At 23mm, the new battery fit neatly within the small allotted space.

Should I run out of used batteries, the cost of ten fresh CR2032's is still only about a fifth of the cost of an OEM replacement battery.  Lithium batteries are compact enough that they make a good choice for a substitute for some of the more exotic batteries.


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## KMoffett (Sep 3, 2019)

Batteries are a pain...but there are ways around as you've done.
My daughter had a battery (one D-cell) chiming clock that ate batteries. So, we made a substitute out of a PVC pipe, a 5V wall wart, and an LM317 voltage regulator. Attached
I found a niced 3/8" craftsman rechargeable drill in our company's junk box. No battery and no charger.  So I turned it into a "corded" drill with a discarded computer monitor power supply brick.  Attached


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## hman (Sep 3, 2019)

matthewsx said:


> Nice, make the next one out of rechargeable batteries and you'll never have to worry about it again
> John


Thanks, John!  I've actually started replacing single-use cells with Eneloop type rechargeables, and do have a bunch of AA and AAA cells on hand.  I'd seriously considered using them for the meter.  What kept me from doing so was the need to wire the 15 cells in series.  Soldering was the only way I could come up with to do the job, so rechgarging would have meant unsoldering and later resoldering the whole pile 



markba633csi said:


> Nice save John- I wonder why HP didn't just provide a 15-cell holder- Maybe some sort of sweetheart deal with Eveready?


Thanks, Mark!  My guess is that "back in the day" there was a goodly number of pretty popular high voltage battery packs ... "B" batteries for portable radios, etc.  So HP just designed around a useful size. 

And of course, not all cell stack batteries are amenable to this trick.  During graduate school, one of the labs I worked at was using a 300 volt "bias" battery as a super low noise DC power supply.  That one would have required 200 flashlight cells for a substitute!  PS - learned something the day I had to replace the battery with a fresh one:  a battery has no "off" switch, and 300 volts HURTS!



RJSakowski said:


> I had a similar experience with a Triplett VOM that I acquired recently.  The battery for the high resistance scale was still available at but great cost.  The battery was a NEDA 210, 30 volts, 180 mah,  and 16 x 26 x 65mm.
> 
> We have several appliances that use CR2032 lithium batteries that crap out when the voltage drops to about 2.8 volts.  I made a carrier from a piece of PVC tubing and loaded it with a dozen used CR2032 batteries.  Some button contacts on the ends and I had a 30 volt battery at essentially no cost.  At 23mm, the new battery fit neatly within the small allotted space.
> 
> Should I run out of used batteries, the cost of ten fresh CR2032's is still only about a fifth of the cost of an OEM replacement battery.  Lithium batteries are compact enough that they make a good choice for a substitute for some of the more exotic batteries.


Likewise, a great save!  Those CR cells pack a lot of volts into a small space.



KMoffett said:


> Batteries are a pain...but there are ways around as you've done.
> My daughter had a battery (one D-cell) chiming clock that ate batteries. So, we made a substitute out of a PVC pipe, a 5V wall wart, and an LM317 voltage regulator. Attached
> I found a niced 3/8" craftsman rechargeable drill in our company's junk box. No battery and no charger.  So I turned it into a "corded" drill with a discarded computer monitor power supply brick.  Attached


Both great saves!  Did your daughter participate in the build?


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## RJSakowski (Sep 3, 2019)

Another strategy for reclaiming old cordless power tools is connect to a newer style battery via a cord.  It seems that there is no common style for battery packs among manufacturers or even for a given manufacturer over the years.  I have used the connectors from a defunct battery for a cordless tool to make a plug for the tool. With a cable attached and the other end connected to a rechargeable battery from a more current tool and the battery either hooked on my belt, I had a usable semi-cordless tool again.


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## ttabbal (Sep 3, 2019)

You can easily charge series nimh packs. It's not as healthy for them as a balance charger would be, but it's possible. They are far more forgiving than lithium. 15 cells though, ugh.


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## hman (Sep 3, 2019)

RJSakowski said:


> Another strategy for reclaiming old cordless power tools is connect to a newer style battery via a cord.  It seems that there is no common style for battery packs among manufacturers or even for a given manufacturer over the years.  I have used the connectors from a defunct battery for a cordless tool to make a plug for the tool. With a cable attached and the other end connected to a rechargeable battery from a more current tool and the battery either hooked on my belt, I had a usable semi-cordless tool again.


Good idea to use part of a battery pack as a plug.  But durn!  Don't ya just hate the proliferation of styles?!?!?  Like a lot of other folks, I've made an "executive decision" to go with just two brands of battery tools.  Got rid of several others that were yet another style.



ttabbal said:


> You can easily charge series nimh packs. It's not as healthy for them as a balance charger would be, but it's possible. They are far more forgiving than lithium. 15 cells though, ugh.


Battery and charger technology is getting pretty wild out there.  I've seen a lot of battery packs with extra contacts (temperature overload and/or monitoring individual cell voltages???).  The Eneloop charger I have will take any number (up to 4) AA or AAA cells, in any combination, but won't do series.  For all I know, it may well have 4 separate charging circuits.  I'm not much of an electronics whiz, so I haven't tried delving into modern chargers.


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## Ulma Doctor (Sep 4, 2019)

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


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## Bi11Hudson (Sep 4, 2019)

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.

.


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## whitmore (Sep 4, 2019)

hman said:


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



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>


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## Downunder Bob (Sep 4, 2019)

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,.


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## markba633csi (Sep 4, 2019)

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


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## Superburban (Sep 4, 2019)

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.


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## hman (Sep 5, 2019)

Thanks to all of you for your responses!



Ulma Doctor said:


> 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.



Bi11Hudson said:


> 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.
> 
> ...


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!



whitmore said:


> 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!



Downunder Bob said:


> 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.



markba633csi said:


> 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
> ...


OUCH!



Superburban said:


> 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


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## Superburban (Sep 5, 2019)

hman said:


> 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.


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## hman (Sep 6, 2019)

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 ...


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## Superburban (Sep 6, 2019)

hman said:


> 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.


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## RJSakowski (Sep 6, 2019)

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.


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## Superburban (Sep 7, 2019)

See, you had a analog PWM controller, and did not even know it.

My ME 77-C/U's, take a 22.5V battery about the size of a 9 volt battery, only for the highest resistance scale, So not having that battery, only cuts out one function of the meter. Not worth the outrageous cost of the batteries. I have considered using a 9V battery, along with a Buck Boost converter to get the volts up to the 22.5V.


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## dpb (Sep 7, 2019)

On the Beavis and Butthead end of this conversation, I was once a young marine, tasked with cleaning out a supply room.  A large box of typical 9v batteries (green, of course) were plugged directly into one another, to make a new, single battery, somewhat longer than my forearm.  When shorted with a couple wires... it was impressive.


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## RJSakowski (Sep 7, 2019)

Superburban said:


> See, you had a analog PWM controller, and did not even know it.
> 
> My ME 77-C/U's, take a 22.5V battery about the size of a 9 volt battery, only for the highest resistance scale, So not having that battery, only cuts out one function of the meter. Not worth the outrageous cost of the batteries. I have considered using a 9V battery, along with a Buck Boost converter to get the volts up to the 22.5V.


Great out of the box thinking!


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