If you use alkalines, sooner or later they will get you.
Same experience with Duracell. Big time leakers. You can definitely get the highest currents with Duracells, if you have a high demand application, but they will eventually leak badly. Store brands often leak too with time (Sams club, Costco) but not with the same predictability as Duracell.
Only exception is Duracell Ultra. I had 8 Ultras that I'd purchased in '98 or '99 (the exp. date was 2006) in an old RF scanner I found not too long ago, and they were still charged and no leakers! In fact, I replaced them with fresh cells, but put some of those Ultras in my wifes sound machine, and they're still kickin' at about 1.3v. Best alkaline I've ever seen for sure, Duracell Ultra. I'll never buy their regular Coppertops again though. Just like Fishinfool said, had too many pieces of equipment ruined with Coppertops.
Energizers don't leak. Rayovac Ultra Pro would be a close second, never had a leaker with the Ultra Pros.
Also, if you have a device/flashlight in storage and would like to leave cells in it, insert a buffer at the tailcap to deny contact while not in use. Even just a piece of paper between the spring and last cell seems to help enormously IME, especially in a hot environment like a glove box or tackle box.
i've had Duracell Ultras leak. they ruined a bunch of my remote controls.
to the OP, you can use alkies if you have to. just don't leave them in the flashlight. take them out in between uses, store the batteries in a plastic container, and you'll be okay.
I have experienced many alkaline leakage problems too, they were not Duracell though but some super cheap Made in China AA cells (price? only $0.16 one pack, comes with four AAs). LOL.
One question always bother me: why is it impossible to recover a flashlight(or any electronic gadget) after battery leakage happen inside? Is it impossible to remove the brownish sticky thing that stick inside?
It's not impossible to clean, but it's not complete either. It must be neutralized with bicarb, rinsed and dried, scraped/sanded off by some mechanical means, and washed and dried again. Then you can thin layer lacquer it, or just make a tube sleeve to isolate the batteries from the tube from now on. That usually works good enough for a flashlight worth salvaging.
Just looked where these Panasonic's where made and it says Belgium on the side
I've never had unused, properly stored alkalines leak.
Used and left in a device, my experience is roughly 1 in 10.
I've gone through 60 - 80 utilitech AAs (lowes) and haven't had one leak - BUT that's probably because I got them so cheap that I swap them out way before they're drained.
Here's a little story that might fit in here.
Months ago I was looking through old stuff in the attic and found a toy that I got for christmas somewhere around 1991. It was a Lego police car with sirens and flashy lights that used 9V alkalines.
I didn't know exactly how long it was up there, at least 15 years I guess. And since that attic isn't isolated, temperatures vary between -10 and +35 °C. If there was a battery left in there, it surely must have leaked and made a complete mess inside.
So when I found that toy I thought "I hope I took the battery out when I stored that thing up here." I pushed the button on the back, and to my surprise the siren went on and the lights were flashing!
I opened up the thing just to see that the battery was in perfect shape. The brand was "UCAR", black on top and golden on the body. I don't even know if that brand still exists today.
Anyway, the battery measured 9.5V and I used it quite some time for testing selfbuilt contraptions until it finally went to battery heaven.
Moral of the story: Some alkalines leak after three months, others won't after fifteen years 
It's the same as with everything else: You'll never know what happens...
Hey Steve, come to think of it, I've never seen a 9v leak either! Even the 'super duty' lead based 9 volts. Interesting.
But very impressive that it still ran. People here dog alkalines left and right, but if you want something that will still turn on 10+ years from now, alkaline is still your best/safest bet IMO. (if it doesn't leak, lol)
i've had a 9 volt explode on me. one of the AAAA batteries inside exploded, tore a hole in the plastic container that it was stored in, and launched the battery cap across the room like a projectile.
i wish i was making it up.
nothing is 100% safe.
+1
Here are mine. These are new and unused, fresh from the blister wrap!
Nope, Lithium primaries are. Not only they have way longer shelf life (12+ years claimed), but they also never leak :Р
They cost a s**t-ton though. :(
Does that include 123s, or are you talking conventional size (aa/aaa/9v) lithium primaries?
I meant 1.5V Li/FeS2 Lithium primaries, I have no idea whether this applies to 3V chemistry (LiMnO2) as well but I’d guess it does considering some CR123A’s have expiration date of 2024 written on them.
Yeah, I'm unsure of the chemistry as well. I have a 4 pack of new lithium AA primaries (energizer E2s) and they all have a voltage of ~1.8, so I'm not sure how that adds up.
This is correct. All alkaline batteries will leak eventually.
The reason is Alkalines use an electrolyte (potassium hydroxide) that is inherently liable to leak due to the high acidic content and internal pressure of the chemistry as energy is depleted. The process of discharge causes a chemical reaction where hydrogen gas builds up pressure inside the cell and ruptures the casing. The potassium hydroxide that leaks will bond with carbon dioxide in the air to form a white crystalline deposit of potassium carbonate which is the corrosive fuzzy deposits often seen after a leak occurs.
I stopped using alkalines years ago due to leakage and switched to rechargables like Ni-Cad, Ni-MH, and Li-Ion, which are much less corrosive and rarely leak or vent when depleted. They can vent when overcharged or abused, but you generally don't need to worry about them leaking when simply left in a device too long.
That’s 1.5V Li/FeS2, put any significant load on them and they’ll quickly drop from 1.8 to 1.4~1.5 (depending on load itself).
Add 14 to the pH. :) And that's why they're called alkaline.
The reason people think 9 volt batteries don't leak is because they are made up of 6 aaaa inside a metal case and if one were to leak then the battery would just be dead, it wouldn't spill all over the place. While taking one apart(for the aaaa batteries) I found one had leaked.
Oops...you're right...must have been thinking of acid-like conditions when I wrote that. My bad.
