1.4V Zinc/Air Battery - Gone Crazy?

<p> I though I knew all one has to know about replacement solutions for 1.35V Mercury batteries, but I'm now facing a problem, that drives me crazy.<br>

Up until now, I've used alkaline 625 batteries - with the expedient of leaving them in the camera with the meter on until voltage drops down to around 1.35V, and then checking the voltage with a good voltage meter before any use and discarding the batteries as soon as they go below some 1.32V. It's a little complex, but it works.<br>

I have now decided to try something different, and I have purchase from Jon Goodman (interslice on ebay) its Tri-dot adapters that enable the use of 1.4V Zinc/Air batteries for hearing aids. The adapters work flawlessly. The problems are the batteries.<br>

After purchasing FOUR six-battery packs from an hearing aids shop, and a corresponding number of increasingly tense discussions with the shopkeeper, the situation is a follows:<br>

When the batteries are taken out from the pack at the shop and the protective label is removed, the shopkeeper's voltage meter register a constant 1.45V - exactly as it should be. But when I do the same at home with the same batteries, the reading is a constant 1.18V. And of course, the meters in all my cameras (Nikon F, Canon F-1, Canonet GIII, various Miranda, etc.) refuse to work and tell me they don't get enough electricity. And, my voltage meter is absolutely correct in reading the voltage of all other batteries in my house.<br>

I don't want to become paranoic and imagine that the shopkeeper is sitting on an entire consignement of defective batteries, and in order to sell them he has got himself a voltage meter providing false readings. But, can anyone here please provide some rational explaination???</p>

 

<p>Are you both using DVMs to do the reading?<br>

1. Some rare meters that may have a 'battery test' feature load the cell down to simulate actual circuit performance. This would drop the voltage one reads.<br>

2. A DVM should not impose any real loading of a battery (huge input impedences), so it is giving you 'open circuit' voltage. If you are using an older, analog meter at home and they a digital, that may account for some difference. But I would not think anywhere near what you are stating.<br>

3. Can the cells be expiring by the time you get them home?<br>

4. Are you making good contact with the battery and are your leads in good shape? I presume yes, in that you refer to other batteries in your house testing out a-ok.</p>

<p>Beyond the above, I'm out of suggestions to explain this issue.</p>

<p>Jim M</p>

<p>Jim is absolutely right. Not all voltmeters and battery testers are created equal. A DVM usually has an input resistance of 1 meg-ohm or even more and will consume just 1 micro-amp of current from your battery. A handheld analog instrument (without pre-amplifier) usually has an input resistance of 10 to 50 kilo-ohms and thus may draw just 100 times the current from the battery than a DVM would do.<br>

Since meter circuits comsume a considerable amount of current, I would rather trust the measurements taken with a analog voltmeter or a special battery tester.</p>

<p>Improperly stored, old out of date zinc air batteries will do that. Look at the expiry date on the package, it should be at least 3 to 4 years away if those are reasonably new batteries. I use the ones from Costco, made by Rayovac, they work fine in all of my Nikkormats and F metering prisms. The newest package of hearing aid batteries sitting in the fridge has a best before date of 2014.</p>

 

<p>Like the last guy said..try another supplier/brand. I assumed you are testing them outside of the adapter at home. I considered the proposal about the leads, but if other batteries are checking right.. I'm stumped. Alos bring your Voltmeter to the shop and show him your problem.. but don't flaunt it. Some things are better left alone, ...try another supplier/brand etc!</p>

 

<p>Also, let's not presume all instruments read right. Look at this example below. The two meters are tied to the same 12 V battery. Note the readings. Which is right, which is wrong, if either?<br>

Calibration is a precious thing. Let's not forget something. A DVM is rated at 0.3% accurate.<br>

That is of FULL SCALE. Set the meter to the 200 V scale, 0.03% of that is +/- 0.6V ! Read a 1.5 V battery on that range, and all you can REALLY say is 'the voltage is probably between 2.1V and 0.9V (1.5V +/- 0.6V).<br>

Switch the meter to the 2VDC range, and its accuracy then is +/- 6mV.<br>

Moral 1 ... use the minimum scale possible that gives you the highest signal to noise ratio.<br>

Moral 2 ... your gear is not God.</p>

<p> Jim (wasting time in the factory)</p><div></div>

<p>The trouble with DVMs is that many people just get confuse resolution and accuracy.<br>

Let's take a normal metric ruler. Usually the scale from 0 to 10cm is divided into 100 segments, each 1mm. So the resolution of the ruler is 1mm. However, you cannot say whether the scale which is supposed to be 10cm long is just 98mm or 102mm. So the end-of-scale accuracy of the ruler would be +/-2mm, whilst the resolution is 1mm.<br>

In general, resolution is much higher than accuracy, and it's hard to find a 3 1/2 or full 4-digit DVM where you can trust the last cipher on the display.<br>

Back in the times of analogue instruments, even in the 2V or 1.5V-range you could not tell whether the reading is 1.26 or 1.24V, and most people were pretty happy with battery testers with this accuracy.<br>

The bottom line is, you should not be too picky when it comes to display the voltage of a battery. It does not matter at all whether it has 1.346V or 1.358V. However, it DOES matter if it has more than 1.4V with no or little load and less than 1.2V with normal load.</p>

<p> </p>

<p> Thank you all for your responses. The expiry date for the batteries was not very far away (mid-2011), but it seemed adequate. The shopkeeper has a small analog meter while I have a larger analog model, but while this might explain the different readings it does not explain the fact that the voltage is actually too low for the cameras to work.<br>

Trying a different brand/supplier is certainly the logical thing to do and I will most certainly do that before giving up, but there is a hiccup. My wife does use a hearing aid, powered by smaller batteries (would not fit into the adapter) that are also given at 1.3-1.4V. I checked one of these (purchased from a different retailer/different brand) and you guess what the reading was: 1.12V. I remain baffled. </p>

<p>all good advice<br>

said better than I could<br>

BUT<br>

let us look at the other side.<br>

when I found out the problem with alkaline cells ( sloping discharge charateristics)<br>

I bought a big package of hearing aid cells<br>

after using several,. here in Pennsylvania that can last several months<br>

normal life is 2-3 months in many locales<br>

the NEW ( old) cells were weak or dead.<br>

DO NOT buy a lifetime supply.<br>

Go in the pharmacy dept. of a large active store.<br>

Target, Wal-mart, kmart. and buy ONE package.</p>

<p>the downside is that as hearing aids age ( not the cells) newer hearing aide may noit use this kind of cell.<br>

and they will be harder to find.<br>

In that case the permanent fix, a shottky diode in series and a silver-oxide cell will be required.<br>

in the meantime, just buy one six-pack at a time in a busy store to get fresh cells.<br>

One TRICK is to seal two of the four holes with nail polish or crazy glue to slow down the drying out process as the cell depends on moisture in the air to make a voltage.<br>

Unless the camera is a waterproof model ignore advice to drill a hole in the battery cap to let in the air.</p>

<p>As things stand today, and pending acquisition of a battery pack a) of a different brand, b) from a different retailer, and c) with an expiry date at least two years away, I've come to the following tentative conclusion:<br>

Zinc/air batteries for hearing aids, while sold at a nominal 1.45V, will in reality on the average produce a much lower voltage. This is apparently not a problem for hearing aids (apart possibly for a shorter battery life than expected), probably because such aids are fitted with some sort of a bridge circuit that would compensate for such variations, but would make them unsuitable for use in cameras, that were designed to depend on the very accurate power supply by 1.35V Mercury batteries.<br>

I thus have a question: does anyone there actually use either Wein cells (= hearing aid 1.4V batteries into a permanent adapter) or standard hearing aid batteries with the Goodman's adapter to good results? After all, it is also possible that both myself and my wife have stumbled into an extraordinary series of bad batteries.</p>

<p>I use the blue tab #675 hearing aid batteries in two Nikkormats and three different F metering heads, they work just fine and have been using them for about four years now. I made my own ring type adapters. Storage of the batteries before use is critical to their long life, high temps will kill them fairly quickly. BTW the Costco ones cost about $12-14 for a pack of 30, much cheaper than the small retail packs at the hearing center, pharmacy, etc.</p>

<p> </p>

<p>Thank you Bob. At least, now I know that this concept does work both in principle and in practice, and thus my problem lies solely with the batteries I've been trying to use. If I ever come to an explaination I will post it here, in order to hopefully save other fellow classic users from running into the same predicament.</p>

<p>There are charts you can find online that show the voltage curve of these batteries. When immediately peeled apart, they usually read 1.4v and then drop soon after to 1.35v, which they stay for their entire life of about 6 months and then promptly just die. They have a very similar voltage curve to the original mercury batteries with a lower life span. To my knowledge, the much much more expensive Wein cells render the same results. These are what I've used in my OM1's and Olympus 35RC for years now with very accurate exposures. I've never used any adapter either, just chucked them in there and when you tighten the battery door the spring at the bottom keeps them from rattling around.</p>

<p>I have used hearing aid batteries for years in my Konicas, but recently have gotten some bad batches. I think the 675 size are seeing less hearing aid use, and the stocks in some stores are getting stale.</p>

<p>patrick is at 100%, you either bought okld cells or defectrive ones. they only way I differ is they eventially the hearing aid cells when the tab is still on, can still die. The very best answer is to connect a shottky diode in series.<br>

THEN a silver-oxide can be used. the ONLY thing that is wrong, is those who insist a alkaline cell<br>

works well, While some spotmatic's have a bridge, not a series circuit. and are much less sensitive to voltage changes. Most older cameras designed for mercury cells, use a series circuit that IS sensitive to voltage changes.<br>

there ARE some newer cameras, including the P&S that use AA cells, that work properly with alkaline cells.<br>

I can see your concern, but many who use classic cameras are very happy with hearing aid cells.</p>

<p>I'm late to this one, but it is the same as with light meters. If you have two meters, they usually will have two different readings of the same thing. If you have three meters, you will have three different readings*. The trick here is to use ONE (1, uno, ein, une, il saymo) meter at all measurement venues. :)</p>

<p>Seriously, next time you go out, take your meter with you, once you have discovered what reading on it you need.</p>

<p>____________<br>

*Ok - I exaggerate a little, but, as I say, do take your own meter with you next time.</p>

<p>Zinc-air cells are really pretty much the same chemistry as in a "mercury" battery. The "mercury" battery also used zinc as the main ingredient, but it also had mercuric oxide which slowly decomposed and gave off oxygen. The oxygen reacts with the zinc, and that causes the electricity. Zinc-air cells just get their oxygen from the air.<br>

The zinc-air cells are designed for much higher current drain, they don't last very long working hard in a hearing aid.<br>

The key thing to remember is that the zinc-air cells leak and corrode something awful if you forget about them. They'll make much more of a mess than a mercuric oxide battery, and much sooner.</p>

<p> </p>

<p>I am seeing quite a few posts saying that meters are not 100% accurate and 2 meters almost always read differently. However, the diffrence should be less than 1.2 to 1.4 V that's a big difference.</p>

<p>Bebu -<br>

The change from 1.2V to 1.4V is a 16.66% change in voltage. If we crudely assume the light meter would be off the same % therefore, and let's say we're in daylight with an EV of 15, then a 16% change would represent about 2.5 stops of error. I'm not sure the meter is linear in its response nor lindear with respect to battery voltage, so this may be baloney.<br>

Just a thought.<br>

Jim M</p>

<p> I don't get wrong reading by the light meters in my cameras (or by Lunasix Pro for that matters) - the voltage provided by these nominal 1.4V Zinc-Air batteries is simply too low for them to work at all. The needle would just move a little, and then stop.<br>

Yes, I'm aware that Zinc-Air would normally deliver 1.4V as soon as the tab is peeled off, and then quickly stabilise at around 1.35V and keep this value constant until quickly dying. This is the very reason why they are used as a suitable replacement for 1.35V Mercury batteries.<br>

But just because of the above, I cannot start to understand what is wrong with the batteries I bought (and which the shopkeeper insist are delivering their regular 1.4V). If those were expired batteries, then given the flat discharge curve they should show a very low voltage or no voltage at all, and not close to 1.2V - which is not adequate to power meters originally designed for constant 1.35V, but still is some voltage.</p>

 

<p>I use type 675 store-brand zinc/air cells (without any adapter or holder) in my older Canon SLRs, and the metering results are pretty good. In general, the best reality check is to correlate with an accurate hand-held light meter.</p>

 

<blockquote>

<p>Bebu -<br />The change from 1.2V to 1.4V is a 16.66% change in voltage. If we crudely assume the light meter would be off the same % therefore, and let's say we're in daylight with an EV of 15, then a 16% change would represent about 2.5 stops of error. I'm not sure the meter is linear in its response nor lindear with respect to battery voltage, so this may be baloney.<br />Just a thought.<br />Jim M</p>

<p>I don't mean the light meter. I meant the voltage meter (DVM, DMM, VOM etc...) an error of 16.66% is just too much for a good working meter.</p>

</blockquote>

 

 

<blockquote>

<p>Bebu -<br />The change from 1.2V to 1.4V is a 16.66% change in voltage. If we crudely assume the light meter would be off the same % therefore, and let's say we're in daylight with an EV of 15, then a 16% change would represent about 2.5 stops of error. I'm not sure the meter is linear in its response nor lindear with respect to battery voltage, so this may be baloney.<br />Just a thought.<br />Jim M</p>

<p>I don't mean the light meter. I meant the voltage meter (DVM, DMM, VOM etc...) an error of 16.66% is just too much for a good working meter.</p>

</blockquote>

 

<blockquote>

<p>The change from 1.2V to 1.4V is a 16.66% change in voltage. If we crudely assume the light meter would be off the same % therefore, and let's say we're in daylight with an EV of 15, then a 16% change would represent about 2.5 stops of error.</p>

</blockquote>

<p>Whilst 16.6% of 15 is indeed around 2.5, light is measured in a logarithmic scale. 1 stop doubles the light, two stops quadruples it.<br>

An LV (not EV) reading of 17.6 is nearer to 1 2/3 stops extra.</p>

 

<p>Don't forget the voltage with the tab on will be low. Not until the tab is off can the oxygen get to the cell inside.<br>

I have also found (with my hearing aid cells) that if you replace the tab to extend cell life when not in use, the voltage will fall back to 1.1V or thereabouts.<br>

Did you perhaps put the tab back on the cell and cover the tiny holes? That would give you a low reading.</p>