Nickel Metal Hydrids

From: Dwight K. Elvey <dwight.elvey_at_amd.com>
Date: Mon Jan 17 16:05:27 2005

Hi
 I would guess that your method is most likely the
best. Keeping them at full charge tends to create
those metal fingers inside that short them out.
Discharging them as packs tends to reverse charge
some of the cells causing out gassing and cell
rupturing.
 I don't know if the NiMH I had was drained by load
or just by sitting around. It is an old machine ( about
13 or 14 years old ). I would guess that these cells
have a similar problem if fully discharged as
a battery stack. The laptop had no normal signs of
wear like a similar one that I had ( video is failing ).
It may have only been used for a year or so and
then just placed in storage.
 Most times when I come on NiCads that have zero volts,
I find the cells to have an internal short. Either
NiMH have something that keeps this from happening
or I was real lucky.
 I do know that wet NiCads ( those with vents ) are
usually shipped with a shorting bar. I would guess that
if one individually drained the NiCad cells, they
could be stored a long time.
 I'll let you guys know how things are after a couple
more days. Hopefully the battery will remain useful.
Dwight


>From: "John Allain" <allain_at_panix.com>
>
>> Most NiCads batteries would not recover from such a level.
>
>How should NiCads be stored?
>Sounds line 0v is a terrible idea.
>I usually put them away at normal discharge,
>about .8-1.0v and then charge a few hours before
>next use.
>All I really know is that:
> o. 300 recharges is about all you can expect, and
> o. topping off is no good
>
>My guess is that unused NiCads could reach 0v
>after a year or two on the shelf. If you restore a
>collectable and then shelve it for 10 years only
>to find it's dead _again_ it won't be gratifying.
>
>It might not be worth sweating this detail, however.
>I have noticed that NiMH prices have gone down
>about half over the last 5 years.
>
>John A.
>
Received on Mon Jan 17 2005 - 16:05:27 GMT