do NiMH batteries leak like Alkaline batteries?

Sorry, I'm sure this question has been asked before, but my search ended up with many threads...

I'm assuming that so many people use AA NiMH rechargables (even on here), that they're not likely to leak in expensive flashlights...but just need assurance

No, they don't leak.

Mr Happy said:

No, they don't leak.

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. . . anything like alkalines
if they get way overcharged , or severly reverse charged they can gass out a bit, and small ammounts of eletrolyte can come out, they are pretty dry inside though.
if you hear hissing, burping from the battery
if you open up a light and significant gas escapes (more than just atmospheric changes or heat cold changes), if the boot on the switch bulges
if you see discoloration or a fine white crystaline powder around the vents , that would be a clue that it happend, the ammount is nothing like the mess alkies can make at all.
and the chances of it happening are rare, can occur if the light with help from the user causes a reverse charge.

I recommend using nimh in ALL devices as far as leaks go they are a non issue. The leaks (very rare) only put powder down which either sticks to the top of the battery vent areas or fall harmlessly not sticking to anything. If nimh had better temperature characteristics people would use them in cars and outdoors because you don't have to worry years later about a ruined light.

never experienced any nimh leaking so far

NiMH and NiCd cells are known as "electrolyte starved" designs. If you were to open them, they would appear to be pretty dry, or just barely damp. If/when a NiMH or NiCd vents, the gas released will contain some moisture, but little or no liquid. On the other hand, alkaline cells have a saturated electrolyte design, so when they vent a considerable amount of liquid can be released.

Cheers,
BG

Just discovered a package of leaking NiMh batteries. 1800 mA made in China. Batteries were never used and package is still sealed. Have a second set of 4 newer NiMh 2100 mA batteries from a different company that look questionable also made in China. I hope this is not the start of a new trend.

[email protected] said:

Just discovered a package of leaking NiMh batteries. 1800 mA made in China. Batteries were never used and package is still sealed. Have a second set of 4 newer NiMh 2100 mA batteries from a different company that look questionable also made in China. I hope this is not the start of a new trend.

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Brand/model would be nice

[email protected] said:

Just discovered a package of leaking NiMh batteries. 1800 mA made in China. Batteries were never used and package is still sealed. Have a second set of 4 newer NiMh 2100 mA batteries from a different company that look questionable also made in China. I hope this is not the start of a new trend.

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LOL

might be alks inside them

I just found an old PMR radio that had 4 leaked Duracell NI-MH AAA 750mah inside, 2 were bad, 2 slightly furry but i dumped them all.

John.

TinderBox (UK) said:

I just found an old PMR radio that had 4 leaked Duracell NI-MH AAA 750mah inside, 2 were bad, 2 slightly furry but i dumped them all.

John.

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The cells probably reverse charged in that device. Its best to check the cells every 6 months and either refresh or charge them every 6-12 months. I'm referring to LSD cells obviously, I run a test on Eneloops once a year on its manufacture date to make it easy to remember.

MidnightDistortions said:

The cells probably reverse charged in that device. Its best to check the cells every 6 months and either refresh or charge them every 6-12 months. I'm referring to LSD cells obviously, I run a test on Eneloops once a year on its manufacture date to make it easy to remember.

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I have Eneloops in almost everything. Once a year, I go through all the electronics that have multiple cells in them, and charge them up. For single-cell devices (like clocks), I just charge them up when they die.

I've never seek a NiMH cell leak. I've seen plenty go completely dead (before the days of Eneloops), but they haven't leaked.

WalkIntoTheLight said:

I have Eneloops in almost everything. Once a year, I go through all the electronics that have multiple cells in them, and charge them up. For single-cell devices (like clocks), I just charge them up when they die.

I've never seek a NiMH cell leak. I've seen plenty go completely dead (before the days of Eneloops), but they haven't leaked.

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I've never seen them leak either. I've reverse charged a couple before but i catch them before they get over -1 volt and within several hours.

I had an off brand and a radio shack NiMH leak.

I had 4 of 8 D size NiMH leak really bad a few years.

John.