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

On 11/01/12 12:12, g.shirville@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.