Shelf life of unused NiMH batteries

[n3eg]

I made an interesting discovery today. I found an unused Motorola radio NiMH battery from 2002 and ran it through the Cadex analyzer. It came up at 27% after cycling, about the same as used NiMH batteries of the same type and age. The battery has no protection circuits or parasitic drain - it was still in an original unopened box. Do NiMH cells degrade with age like Li-ion cells, or was this a fluke?

 

[Eugene]

Seems low to me, I have Sanyo's from back to 1999 that average around 80%

 

[TooManyGizmos]

.
They need to be used routinely - and cycled .........

or recharged every few months .


They don't like to be ignored .

.

 

[SilverFox]

Hello N3eg,

Did you happen to check the voltage of the pack before you cycled it?

I would guess that it was pretty close to 0 volts.

When NiMh chemistry sits at 0 volts for any length of time, the electrolyte oxidizes inside the cells. This ruins them.

On the other hand, if you cycle a battery pack frequently and keep the voltage above 1 volt per cell, they can last a long time.

The seals in a NiMh cell can dry out and allow some electrolyte to escape from the cell, but this is not the same as the oxidation that takes place within Li-Ion cells.

Tom

 

[n3eg]

Another interesting thing: An identical battery that was taken out of the same box and charged once 7 years ago, had 3 of 6 cells shorted and wouldn't even charge.