I can't find any info on this.  

Say you put an unopened pack of any given brand NiMH double A's on a shelf, how long do you think they're good for?

Will they self-discharge themselves to death?

I'll be buying mostly Eneloops, but getting a bunch of Lacrosse's with the new chargers.

   Well I've been told that NiMH batteries should be recharged, even though not used, every six months due to self-discharge.  

   Now I take that with a grain of salt.  I have AA's NiHM batteries that's been in my camera flash unit for a year and has not self-discharge.  Yes I did use the batteries till it was low in charge.  The brand I use are Energizers.

I've heard ~6 months as well for most NiMH.

I've been using eneloops, and haven't seen much of a difference after they've sat for over a year (vs freshly charged).

ETA: I also got some La Crosse NiMH batteries with their charge, but I have only had them about a month.

NiMH self-discharges at roughly 1% per day after an initial 10% discharge in the hours after charging.

Basically, they'll be effectively discharged after 60 days *under real world conditions* (heat, etc.)  

I make it a point to charge mine around the first of every even numbered month.

Do not "run them down" before charging as you may damage the cells.



NiCd batteries will last months and still retain some charge.  Best to cycle them empty before recharging to minimize "memory" effect.


LiIon batteries are only good for a couple hundred charges before their capacity begins to diminish.  You'll get about 400 charges in before they are pretty much worthless for anything constructive.  Hint for the day: When you get a new laptop, remove the battery after it's charged so it doesn't "charge" every time you plug in and only use it when you need it where power's not available.

John

I have some Energizer NiMH that I was wondering the same thing about.  In order to test this, I charged them up and put them in my handheld GPS.  I've used the GPS a couple of times, but have mainly been checking the unit once every month or so to check the battery status.  Currently I am approaching 4 months in the device and it is still showing about 40% battery life left.  I would have to suspect that if they were not in a device, they would last a bit longer.

Wow,  it sounds like quite a hassle to have too many batteries.  

Right now I have about 20 in rotation, with 4 on the charger and 2 spares.  

What I wanted would put me at about 85 total, I like that number, but I'd have to charge 60 batteries for no reason every 6 months.

I guess I could keep them in those 8 cell holders, date them, and do like 1 set a month.  That might not be too bad.

I'm glad I asked before I spent money.  Maybe I wont buy a lifetime supply like I wanted to, I dunno.

You guys leave NiMH batteries in a flashlight or other high-drain device and you're going to be disappointed if you expect they are going to have anything left after four months, much less six.

J

I'm not meaning that.....I know the nature of the battery itself.  I've used them in everything I own now for 2 years.  That's why I want eneloops and more lacrosse chargers.

If I leave them on the shelf for 5 years without charging, I know they'll be dead.  I don't care about that.  

What I'm wondering is, at what point will they no longer take a charge and be garbage.  

If I seal them in mylar like rice will they be trash in 20 years?  

What I want is simply a stockpile of them for the future.

I'm not meaning that.....I know the nature of the battery itself.  I've used them in everything I own now for 2 years.  That's why I want eneloops and more lacrosse chargers.

If I leave them on the shelf for 5 years without charging, I know they'll be dead.  I don't care about that.  

What I'm wondering is, at what point will they no longer take a charge and be garbage.  

If I seal them in mylar like rice will they be trash in 20 years?  

What I want is simply a stockpile of them for the future.

From what I've read, its not really a time limit, but charge-discharge cycles that will kill a rechargeable battery. This, along with the memory of some types is what limits their life.

If you have batteries that are 2-3 years old, but have never been used, I think with a refresh they will be just fine. Store them in a cool, dry place will help as well. As far as 10+ years, I think commercial rechargeables are too new to tell.

ETA:


I've had 4 Eneloops in the flash for my camera for about 4 months now, taking a few hundred photos (not all with flash, but quite a few), and they are still going strong. I even have been manually firing the flash for fun trying to get them drained so I can figure out their lifespan.

At over one year and less than 2 90% of my non slow self discharging NiMH were eeither not capable of taking a charge or held 50% or less capacity because I left them on the shelf.  Eneloops would all still be able to fuction and keep a charge at 2 years if stored with a full charge.  A standard Energiser charger would not charge any of those batteries.  The LaCrosse would not charge any of them either. My MAHA C-9000 let some run 50% with a break in cycle.  

Letting a NiMH drain to zero via self discharge and just sit there kills it dead as can be.

Any rechargable not topped off in 20 years will be trash no matter what.