"Magic" AA batteries in a home device?

[DaveC426913]

TL;DR

My battery-operated door lock will not work with any other batteries than those in it now.

I am mystified. My number-combo door lock (one of two I have) is powered by 4 AA batteries. It has been working for so long I don't remember when I installed it - musta been ten years at least. The batteries have begun to run down - it labours to retract the dead bolt now - so it's time to replace them, as I do every year or two.

Grabbed four identical batteries out of the same box as the ones currently in the device (same expiry date - ten years from now). New batteries do nothing - device does not work. Will not light up the LED or beep or anything. Presumably, batteries from box are stale?

Battery meter says no, batteries are fine. I accuse battery meter of lying and go back to old batteries that still work - barely.

(I know these types of meters are not very reliable for absolute values, but I get pretty good values for relative comparsion.)I go out and buy a fresh batch of batteries - same brand (Energizer), but these one I notice are "Max" (I guess they're heavy duty). No joy. No light, no beep, nothing.

I try the original batteries, which work every time, even though slowly. I flip back and forth between originals, old replacements and fresh-from-store a dozen times. Results are exact: Originals work 100% all others work 0%. Combinations of old and new result in 0% - IOW, only all four original batteries work.

That being said: I can get replacements and fresh-for-store to work temporarily if I apply pressure by jamming my hand on the batteries.

As far as I can determine, it isn't oxidation on the contacts, or a bent contact, or weak batteries, or anything like that. I've tried six ways from Sunday.

My best hypothesis is that the device refuses to operate if the voltage/current is too high - except why does it work if I jam my hand on it?

Thoughts?

 

[.Scott]

My guess is that there is a missed connection with the new batteries.
I would try replacement batteries that look like the old original ones - in the details of the form.

Also, those two black wires likely run to a through-hole soldered connection on the PC board. If that's the case, a little bit of sanding should allow you to get a good connection with the voltmeter probes. Take that in-circuit voltage measurement with the original and the fresh batteries. My guess is that the voltage will be zero (or very, very low) with the new batteries.

 

[hutchphd]

In my experience it is always the positive end of the AA battery (the protruding end) that is the issue. I think many devices recess that battery contact in the case to inhibit effect of wrong way insertion.
Because you can get contact by mashing it may be sufficient to insert the batteries and close all the retaining doors, making the plastic box more rigid. Smack the box sharply with the battery doors closed to see if you can "settle" them onto the contacts. And those battery testers work fine IMHO.
If you have a meter put it on V and check the voltage at each junction: black at - end and poking each in turn...you should get 1.5V,3V,4.5V,6.V.

If the locks misbehave are you out in the cold?

 

[Baluncore]

In my experience it is always the positive end of the AA battery (the protruding end) that is the issue. I think many devices recess that battery contact in the case to inhibit effect of wrong way insertion.

I agree. The buttons on the (+)ve end of batteries have become lower profile over the years, and the plastic around the holder socket has become thicker. Carefully reduce the battery holder plastic at the (+)ve end, to allow the battery to make contact, or insert a thin metal shim to make a contact if there is sufficient length in the holder.

 

[anorlunda]

or insert a thin metal shim to make a contact if there is sufficient length in the holder.

I used a ball of aluminum foil to make a shim in such cases. The battery can crush it to the needed size.

 

[Baluncore]

I used a ball of aluminum foil to make a shim in such cases. The battery can crush it to the needed size.

If it works, great. I use a bent bronze shim and avoid Al foil because Al has a sapphire coating and will corrode to crumb in marine environments.

 

[sophiecentaur]

It staggers me that we should have to be discussing this problem at all. At one time, we expected old discharged batteries to split and leak nasty stuff all over the battery holder. Now, at least, that doesn't often happen.

But this contact problem is criminal. Is it a conspiracy between battery makers and the companies that sell us more and more battery operated devices? I have become totally numbed by the fact that I buy pack after pack of AA and AAA cells. Why should we accept this? Do we have an option?
Even the mains adaptors are dodgy (except, of course, for the fancy Apple ones which cost a fortune).

 

[anorlunda]

I have become totally numbed by the fact that I buy pack after pack of AA and AAA cells. Why should we accept this? Do we have an option?

Have you considered the quality of the battery holders as opposed to the batteries?

 

[sophiecentaur]

Have you considered the quality of the battery holders as opposed to the batteries?

You're probably right. All Duracells are the same quality and that can't be said of the devices they power.

 

[Baluncore]

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. The positive terminal button should be a minimum 1 mm high and a maximum 5.5 mm in diameter, the flat negative terminal should be a minimum diameter of 7 mm.

https://en.wikipedia.org/wiki/AA_battery#Dimensions
So the positive-terminal shroud on the battery-holder needs to be less than 1 mm deep to meet that spec. There also needs to be a minimum length of 1.3 mm spring in the holder.

 

[Tom.G]

1) Another (remote) possibility is that your device actually needs Carbon/Zinc (LeLanche) cells. The fresh open-circuit voltage is slightly higher than the now-common Alkaline chemistry. The Carbon/Zinc cells are frequently labelled "Heavy Duty" without the "Alkaline" labelling.

I have an old RCA VTVM (Vacuum Tube Volt Meter) that uses a 'D' cell for resistance measurement. The Resistance range will not Zero with an Alkaline cell, but works fine with a Carbon/Zinc cell.

2) Another possibility is the battery holder having a bad contact. Those holders that have a rivet as a contact sometimes are loose or have a bit of hidden corrosion under the rivet head. If you are adept at soldering, a bit can be added to bond the rivet to the associated conductor, without melting TOO much plastic.

Progress notes please.

Cheers,
Tom

 

[f95toli]

Our carbon monoxide alarm only works with specific models of AA batteries. The manual actually contains a list of batteries that will work. My assumption is that the circuit actually -for whatever reasons- somehow measures the EMF to make sure it is in the right range and turns off it is not.

I don't think it is the case here, but I thought it might be worth pointing out that some circuits behave like this by design.

 

[Tom.G]

They measure the internal impedance of the battery. IIRC, this is done by measuring the voltage drop during the Red "Heartbeat" flash of the LED. At least that is how it's done to detect an end-of-life battery condition.

 

[xs2022]

You're probably right. All Duracells are the same quality and that can't be said of the devices they power.

Duracell is the best in my experience.

 

[cmb]

I'm with the short +ve nipple suspect. I have routinely had this problem with rechargeable AAs where they seem to shave that nipple height right down to the spec minimum to get a bit more volume in the body of the cell.

You need to put the batteries in then, with it 'on' probe back from the power tracks to see where the power 'stops'. Often, when you insert the probe onto the +ve end the thing starts because you've just closed the connection to the terminal.

 

[George Keeling]

I have become totally numbed by the fact that I buy pack after pack of AA and AAA cells. Why should we accept this? Do we have an option?

Yes. Buy a battery charger and a sufficient rechargeable batteries. No more recycling polluting old batteries and I haven't bought a battery for years.