At 02:24 PM 10/12/2004, Falcon Wireless Tech Support - KF4HAZ wrote:

>I used Makita cordless tools and NiCd packs for 10yrs.
>The packs got discharged and re-charged @C/1 rate using temp rise method a 
>minimum of 5 cycles per week for each pack and never a problem in 10yrs.
>But when I changed my line of work, they would often sit for weeks or 
>months without use, that killed all of them.
>NiCd packs are meant to be worked hard and often, they are not well suited 
>for the average "occasional use" home user.

Long term "trickle" charging, in excess of the self discharge rate, is a 
bad thing.
It electrolyzes the water into H2 and O2.
The hydrogen can creep out through the metal, and through the seal, even 
faster if it's not perfect. The oxygen combines with everything it can, and 
it also tries to escape the seal.
Lost electrolyte and corrosion is what eventually kills the cell.
You can buy cells designed to take it, they have excess plate capacity on 
one side, and some expensive catalyst to encourage the H2/O2 
recombination.  This takes down the max capacity per cell though, and it 
costs more.
You'll see a nice sharp thermal spike at the end of 1C charge on these 
cells, the ones that don't have it (regardless of the mfgr's claims!) are 
mushy, and the temperature rise can be almost linear over the charge time.

Nicads like temperature extremes better than NIMH's.
They don't reccomend charging (at all!) above 40C, which is not all that 
warm, especially sitting in the passenger compartment of a car.  

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