AR15.Com Archives
 shelf life of uncharged NiMH batteries?
dosquattros  [Member]
10/16/2009 9:24:31 AM
I've got some AA and AAA NiMH batteries laid up, and have assorted charging strategies. Does anyone have an idea of what the shelf life is on these if left uncharged? Thanks guys!
Paid Advertisement
--
SparticleBrane  [Member]
10/16/2009 10:43:47 AM
Originally Posted By dosquattros:
I've got some AA and AAA NiMH batteries laid up, and have assorted charging strategies. Does anyone have an idea of what the shelf life is on these if left uncharged? Thanks guys!


Not very long at all. It is recommended that you recharge NiMH batteries once/month to keep them working.

NiMH rechargeable batteries self-discharge over time, and if the cells get below a certain voltage it will physically damage the cell, thus making it incapable of holding a charge and rendering it useless.


Of course, if you treat the batteries nicely they'll last 800-1000 charges without losing significant amounts of capacity.
autumnsong  [Team Member]
10/16/2009 10:58:46 AM
Originally Posted By SparticleBrane:
Originally Posted By dosquattros:
I've got some AA and AAA NiMH batteries laid up, and have assorted charging strategies. Does anyone have an idea of what the shelf life is on these if left uncharged? Thanks guys!


Not very long at all. It is recommended that you recharge NiMH batteries once/month to keep them working.

NiMH rechargeable batteries self-discharge over time, and if the cells get below a certain voltage it will physically damage the cell, thus making it incapable of holding a charge and rendering it useless.


Of course, if you treat the batteries nicely they'll last 800-1000 charges without losing significant amounts of capacity.


So, just to be clear.... What you are saying is that NiMH batteries come from the factory pre-charged and you MUST immediately start the charge discharge cycling or the batteries will be ruined? I was under the impression that NEVER used/charged NiMH batteries could be stored but once you started charging them you had to continue. Am I mistaken? Is there a link that confirms this? Thanks.
Desert_AIP  [Team Member]
10/16/2009 11:02:38 AM
How do the batteries not get damagaed hanging on the rack in the store for months?
warlord  [Member]
10/16/2009 11:07:20 AM
I really don't know for sure, but I would say probably indefinitely to the question in the OP because the NiMh life is determeined by the number of discharge/charge cycle. This is why the instruction sheets recommends discharging it and then recharging and not recharge even though it is not fully discharged.
halfslow  [Member]
10/16/2009 11:17:04 AM
Enerloop NIMH batteries are the only ones I know of which are worth having at this time:

http://us.sanyo.com/Batteries/About-Eneloop-Batteries

The have very little of the problems that most batteries have.

SparticleBrane  [Member]
10/16/2009 11:33:23 AM
I've read lots of conflicting information –– some people say to charge them (whether or not they are used) once a month, once every 3 months, or sometimes not at all. I just read something saying that NiMH can be stored 'indefinitely' when empty or full. But then it said to avoid the memory effect, make sure you do a recharges/discharges before real usage.


I know with the battery packs I use in my HID diving light (13.5aH NiMH packs), it is recommended to charge them at least once/month as best practice, although they can probably tolerate sub-optimal conditions.
dosquattros  [Member]
10/16/2009 11:46:29 AM
I found this FAQ, which seems to indicate that they can be left "as bought" for quite a while, and that as mentioned by others above, once put into service they should be cycled a few times a year to maintain performance. This is all in the manufacturers words though. I appreciate hearing your real-world experiences...

Battery Storage Recommendations

Thanks guys!
criley  [Team Member]
10/16/2009 12:20:32 PM
Originally Posted By halfslow:
Enerloop NIMH batteries are the only ones I know of which are worth having at this time:

http://us.sanyo.com/Batteries/About-Eneloop-Batteries

The have very little of the problems that most batteries have.




RayOVac has hybrid batteries that are also very good.

Duracell has just come out with some recently as well.

They both can hold the majority of their charge for about a year.

5subslr5  [Life Member]
10/16/2009 12:45:51 PM

Originally Posted By criley:
Originally Posted By halfslow:
Enerloop NIMH batteries are the only ones I know of which are worth having at this time:

http://us.sanyo.com/Batteries/About-Eneloop-Batteries

The have very little of the problems that most batteries have.




RayOVac has hybrid batteries that are also very good.

Duracell has just come out with some recently as well.

They both can hold the majority of their charge for about a year.



They both can hold the majority of their charge for about a year.


Right will hold roughly 80%.

Here's what I do/am going to do. I charge all my rechargeable batteries immediately upon receipt. I'm going to recharge at the end of one year.

NOT saying that I'm correct.



5sub
Ranchhand365  [Member]
10/16/2009 5:46:47 PM
I design and manufacture NiMH battery chargers (15 yrs).

From the FAQ:

"Either fully charged or discharged, Nickel Metal Hydride (NiMH) batteries may be stored indefinitely . . .
In either cased (charged or discharged) the capacity is recovered within two or three charge / discharge cycles."


This is my knowledge of storage.

After a long storage, you will want to ‘form up’ the cells again thru repeated charge / discharge cycles. You need to do this when the cells are new also. In our experience, full capacity of a Ni cell is not realized until 10 - 40 cycles (depends on the cell). Probably +95% capacity is achieved in the first five cycles. NASA storages their Ni batteries at slightly above 0°C (freezing) to prevent condensation. They put every battery pack thru a 40 cycle charge / discharge routine upon initial receipt and a couple of times right before flying the pack.

Edit to add: You don't want to charge the batteries when they are hot or cold. Room temperature is good. If the cells are getting hot to the touch during charging, get a new charger. (I’m talking hot, not a little warm.) This boils off the electrolyte and reduces cell capacity.
Paid Advertisement
--