[amsat-bb] Re: Question of the day!

[Gordon JC Pearce]

On 11/01/12 12:12, g.shirville at btinternet.com wrote:
> Hi All,
>
> It is "said that" NiCad battery cells usually fail to "short circuit"
> and that Lithium Ion ones usually fail by just loosing their ability to
> hold a charge viz they go "open circuit"
>
> Is this true or....?
>
> many thanks
>
> Graham
> G3VZV

It certainly *seems* to be true.  We have radios with NiCads that are 
still struggling on with reduced capacity but when they go, they go dead 
short across the cell.  This is because little whiskers of cadmium 
eventually grow across the electrolyte.

NiMH doesn't seem to do this, and can otherwise be considered a drop-in 
replacement for NiCad.

The Lithium Ion batteries we use seem to hold up pretty well until about 
600 cycles, then fall off very rapidly.

-- 
Gordonjcp MM0YEQ