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Simpson users - D cell replacement?

N

N8Nagel

Addicted Member
evening all,

A while back I got a Simpson 260-8P needing minor repair. Most of which was due to leaky alkalines. As I hate alkalines and hate leaks I got a little adapter for the D cell which holds 3 AA cells, and used NiMHs.

When I needed to measure a low resistance, however, I could not zero out the meter on the Rx1 scale. Even after charging up the NiMHs and immediately trying it, I still could not zero. This tells me that apparently the slightly lower voltage of the NiMHs makes them unsuitable for this particular application.

It would be easy enough to test if I had any alkalines laying around, but I don't. Anyone else see this? Am tempted to get some lithium primary AAs and keep using my adapter, but those are actually a little spendy.

thanks for any advice...

at least the "9v" Tenergy Centuras seem to work well both in Simpsons and Flukes
 
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Use a Duracell alkaline. My Triplett (same technology as your Simpson) has a "D" cell that is marked with an expiration date of 03/16 and is still working fine. An ohmmeter will only see intermittent use, so the battery should last as long as the shelf life. The other battery in this meter is a 30 volt (for the highest resistance scale) using an Eveready 413 that was installed in 1995. I generally prefer Duracell over Eveready but I don't think Duracell makes a replacement for this.
 
The problem I have with alkalines is IME they are crap and always leak. Maybe others have better luck, but for the last 10 years or so I've been trying to go all NiMH not because I'm a granola munching hippie but because I got sick of wasting my Deoxit on battery contacts.
 
Alkaline salts are soluble in water. I've had quite a few devices with leaking alkaline cells and they nearly always clean up with hot water and a moderate brush. If you remember zinc-carbon cells with sulphuric acid paste (long before alkalines) you would appreciate the ease of cleaning up after a leaking alkaline.

As for the Simpson, 3 NiMH AA cells won't produce sufficient current to zero the movement on the RX1 scale. The movement requires about all the 10 watt-hour rating of a fresh D cell. Three AAs in parallel would be lucky to crank out much over 7-8 Wh for more than a few seconds unless they are LiPo cells, and those do like to spontaneously catch fire in confined spaces.
 
N8Nagel said:
The problem I have with alkalines is IME they are crap and always leak. Maybe others have better luck, but for the last 10 years or so I've been trying to go all NiMH not because I'm a granola munching hippie but because I got sick of wasting my Deoxit on battery contacts.
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So replace the alkalines a little more frequently. Been using alkalines in my 260 with no leaking issues for the last 40 years.
 
Not a fan of junky alkalines, had a bunch of Rayovac go leaky in the package at work. Had decent luck with Duracell tho.
 
Watthour said:
Alkaline salts are soluble in water. I've had quite a few devices with leaking alkaline cells and they nearly always clean up with hot water and a moderate brush. If you remember zinc-carbon cells with sulphuric acid paste (long before alkalines) you would appreciate the ease of cleaning up after a leaking alkaline.

As for the Simpson, 3 NiMH AA cells won't produce sufficient current to zero the movement on the RX1 scale. The movement requires about all the 10 watt-hour rating of a fresh D cell. Three AAs in parallel would be lucky to crank out much over 7-8 Wh for more than a few seconds unless they are LiPo cells, and those do like to spontaneously catch fire in confined spaces.
Click to expand...

My understanding was that NiMHs actually had lower internal resistance than alkalines and therefore even though a lower nominal voltage were actually better for high draw applications?

I'm tempted to try a Centura D cell but that's kind of an expensive experiment.
 
I've been using rechargeable lithium ion D cells and 9 volt batteries. Also Exell 411A 15V alkaline batteries in my Weston and Avometers.
 
Depends on the circuit. VOMs are probably "low current" devices but are voltage sensitive, may need to modify the circuit to deal with the lower voltage.

IMHO in analog voltmeters, alkalines should not leak unless you're somehow constantly draining the batteries, perhaps in FETVMs. In fact in passive analog VOMs it's fine to use "heavy duty" batteries - I use a set of cheap carbon zinc batteries in my Eico analog VOM and it's been fine, haven't needed to swap them in years. They'll dry out before they leak, of the ones I've worked with. Carbon Zinc batteries use an acidic electrolyte immobilized in the separator (usually an acidic ammonium salt), and there's much less electrolyte than in an alkaline cell. BTW, "dried" alkaline battery electrolyte seems sparingly soluble in water, or at least the aftermath is hard to clean with water. Using vinegar or dilute muriatic acid works better.

Incidentally my Eico analog VOM drains about 150-200mA in Rx1 mode. A NiMH has no problem supplying that much current, but breaks down because its voltage is too low to calibrate with the circuit designed for 1.5V nominal. A Carbon Zinc D cell will also eadily pass 150-200mA, it needs to do so for old incandescent flashlight bulbs!

NiMH is even worse in the Rx10K scale where many use several batteries in series to up the voltage. My Eico uses four AA's and there is over a volt less voltage of the set of 4 with NiMH cells. Plus the self-discharge of NiMH has its own annoyances.

Also avoid crap and phony alkaline batteries and don't try to recharge any alkaline batteries. In my opinion as well, avoid Ray-O-Vac alkaline, I've had plenty of these leak. I've had a few "Hazard Fraught Tools" alkalines (weakly) explode so that's yet another potential problem. I've had several Duracell leak too but don't remember if I tried charging them or they also could be phony Duracells (those chinese counterfeiters make duracell lookalikes.) Not sure but I suspect Energizer also has their fakes.
 
Clean up alkaline chemical fouling with white vinegar neutralizer and a toothbrush, followed by clear water rinsing. Some NiCads will also leak, worse than alkaline cells. Same cleanup procedure.
Don't leave cells in infrequently used items and occasionally check battery bays in items that have them.
 
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On the other hand I suspect people are aware that carbon zinc batteries deplete the case when it's used up (as well as the manganese). There's not enough liquid in them to really leak (they are really kind of dry in dry cells) but if they get wet from an EXTERNAL source, then there's a world of pain...

Then again, there's more problems than water just getting into batteries (meter movement?)

I have an old tiny analog VOM that has a sole Rx1K range for resistance that uses a single AA battery. It has a heavy duty manganese-zinc battery. Granted it is using a steel coat that is rare these days for cheap cells.

I have yet to change it after 30 years and last I checked within 6 months or so, it was still working...

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On the other hand I also have a Radio Shack autoranging analog FETVM. It uses 4xAA. I calculated out that the batteries would last no more than 1000 hours or so due to quiescent power draw when "turned on" mostly due to the LED indicators and probably the op amps. I'm always worried about leaving it on, when I got it used it had "crystal mess" in it, and leaving it on by mistake likely will result in more "crystal mess."
 
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N8Nagel said:
A while back I got a Simpson 260-8P needing minor repair. Most of which was due to leaky alkalines. As I hate alkalines and hate leaks I got a little adapter for the D cell which holds 3 AA cells, and used NiMHs. When I needed to measure a low resistance, however, I could not zero out the meter on the Rx1 scale. Even after charging up the NiMHs and immediately trying it, I still could not zero. This tells me that apparently the slightly lower voltage of the NiMHs makes them unsuitable for this particular application.
Click to expand...

The original battery was a zinc-carbon cell which delivered a voltage of 1.56 VDC when new, and reasonably constant over the early portion of its life. Alkalines have a slightly higher initial voltage of 1.6 VDC which rapidly drops with use and with load, as the impedance of an alkaline cell is quite high. This is why battery-powered devices use substantial capacitance to decouple the power supple from the battery as it sags under load. The drop with load is not an issue for the meter, of course, as only trivial currents are used.

A NiMH is a terrible battery for this purpose as it is a nominal 1.5 VDC when fully charged, but rapidly dropping to 1.25 VDC @ 50% charge, then 1.0 VDC when nearly discharged. The modern NiMH are much better for self-discharge, but one needs the newer technology, as the voltage in older units rapidly declines below 1.5 VDC.

Batteries maintaining a constant voltage until the very end of life include mercury and silver oxide batteries. This is why those batteries were used in light meters for cameras, pocket calculators, and test equipment.

You may recall Dynaco, EICO, and others using a brand-new zinc-carbon battery to deliver 1.56 for bias adjustment. This is why.
 
N8Nagel said:
Got an example? I thought rechargeable lithium ions were 3.7V not 1.2/1.5V?
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Two different technologies:
Li-ion (as commonly used in portable tools and battery packs) has a nominal voltage of 3.60 VDC / cell, but this varies as high as 3.7 to 3.85 VDC.
Lithium polymer can be made in 1.5 VDC per cell, and this is the standard AA, AAA, C, and D cells.​

A handful of manufacturers make Li-polymer batteries and these are easily purchased on Amazon, albeit at $7 to $10 apiece.

The difficulty with the polymer batteries is high cost, lower energy density, swelling, and a propensity to combust if damaged.

I had looked into lithium batteries for flashlights and came away shaking my head at the cost and risks, instead choosing NiMH with low self-discharge rates.
 
Any reason why I shouldn't try something like the Energizer Ultimate Lithium AAs (these are not rechargeables, but have a very long shelf life and IME don't leak like alkalines)? Those seem like a better fit as they are closer to alkalines in nominal voltage. I just really, really, really have a strong aversion to using alkalines or carbon-zinc cells in anything, because of repeated bad experiences.

I can't remember if it was this unit or the other one I had; one of them I had to replace the piezo as it was blown off the board (I'm guessing someone measured a voltage while the switch was in the wrong position?) but on both, I had to order replacement battery contacts as the D cells had leaked in both to the point that the old battery contacts were so corroded as to be unsalvageable. At this point I actually lump alkalines in with carbon-zinc as cells that manufacturers consider an obsolete, "bargain basement" product and therefore make them as cheaply as possible. I've had that opinion for 10 years or more when I noticed a sharp rise in the amount of equipment that I had that was getting damaged by leaky cells.
 
Lithium batteries have a problem of voltage drop with discharge, and the voltage may drop 1.7 VDC fully charged to 1.2 VDC when discharged. The higher voltage may affect your meter calibration. The drop depends upon the current drawn.

Yeah, starting about maybe fifteen years ago alkalines started leaking. The Duracel which used to be better became worse. I have had too many fancy flashlights, portable electronics, and remotes, ruined by alkalines.

I am in the process of converting all of them to NiMH which do not have the same corrosion issues and seal failure.
 
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