You can reverse the above and repair an A23 battery!

A23 batteries are still available, though they began as photoflash

batteries for cameras nobody uses anymore. The reason A23s are still in

use is that they are just right for simple remotes that aren't really

used much, such as your garage door opener remote (2 1-second presses

per day? 4, maybe?). The A23's 12 volts allows easy design of a door

opener which puts out an infrequent but powerful burst of

radio-frequency signal that is strong enough to work reliably from a

fair distance under poor conditions.

Now back to the battery.

Of course your door opener will fail at the worst time. It has only

been two or three years since you replaced the battery, and that one was

the second one in your A23 pack. Amazon will get you another pack, but

it will take a week. Maybe you can find the battery locally, but don't

bet on it these days.

But you can repair it !! Think

about it. Why should an alkaline battery fail in two or three years of

minimal use? The rating of the A23, 40 mAH (milliampere hours), is

144000 milliampere seconds. If each press is 1 second long and draws 10

milliamperes from the battery, you should get 14400 presses from an

A23. At four presses per day, that's 3600 days of opening your garage,

or about ten years from that little battery! And most of us will

agree that an unused alkaline battery will still have most of its life

after ten years on the shelf, so it shouldn't be dead of old age in only

two or three years. So why is my garage door opener battery dead in

two years?

I took the battery apart to find out why my

digital voltmeter read the battery as having only 7 volts output. Each

cell measured over 1.54 volts. They were like new. All right, then,

why doesn't the battery give me 1.54 x 8 = 12.32 volts? It's that black stuff on the LR932 cell terminals from the cheap plating

that the manufacturer used. There are 8 LR932 cells, so there are 16

metal surfaces that can corrode, and corrode they had. The cells had

not leaked; it is the kind of corrosion that happens with low-voltage contacts made by inappropriate metals,

which is what the Chinese who made the cells used. Those of us who

have designed or repaired electronics for a living have seen the same

problem of contact corrosion resulting from the wrong plating in the

wrong place many times.

So now let's fix the battery and

get that garage door to open again. Take the battery apart, being

careful to save the additional metal terminal parts and washers at each

end. There's a spring under the + contact (red), so be ready for that

and protect against it flying away. If you have a voltmeter, check each

cell, making contact on the side of the cell for + and on the small end

for -. You will not have to press very hard. I think you will see

what I saw--the "dead" battery just has corroded contacts on the cells

that are inside; otherwise the cells are fine.



Get some sandpaper,

100 to 200 grit (medium fine), and rub each end of each cell until the

black stuff is gone. Don't overdo it--just make most of the black stuff

go away. After that, wash each cell using a little rubbing alcohol or

distilled water and a Kleenex or Q-tip to get the sandpaper dust off the

cells.

Get a two-inch strip of blue painters' masking tape,

the kind that isn't super sticky but sticky enough, fold the ends about

a quarter inch, and attach it to your work surface so it is flat with

the sticky side up. Assemble the battery horizontally with the cells

touching in series just as it was when you took it apart. Now take

another piece of the blue masking tape and gently attach it to the sides

of the cells that the first piece of tape does not touch. Push the

cells together and smooth the second piece of tape around the battery.

The goal is to neatly cover the battery with one layer of tape.

When you are done

you'll have a blue cylinder of tape around the battery. Don't close

the ends; instead, open them with a pencil or small tool. Collect the

small terminal parts you saved and put them back in place by pushing

them into the cylinder and tweaking their position. (Hint: The end of

each terminal that sticks out has a washer on it. And don't skip the

spring.) Now push on each end where the terminal is, and make sure it

is square, and lastly push on both ends at once. Now close the ends of

the tape cylinder by folding over the tape. Trim the tape with an Xacto

or other sharp knife so that the tape does not build any higher than

the terminals, and clear away the tape where the terminals are. Test

the battery for 12 volts if you have a meter, and then go open the

garage door again.

How long will this last? Probably at least long enough to get another battery,

but if your door opener remote has strong spring pressure on its ends,

it could be two or three years till the cells have to be cleaned again.

If the cells had been plated properly for a few more cents, the A23 battery would never have had to be taken apart.