On Fri, 18 Jun 2004 10:01:19 +0000 (UTC), "James"
wrote:


"Peter W. Meek" wrote in message
.. .
On Wed, 16 Jun 2004 10:34:33 -0400, Glenn Ashmore
wrote:

NiCads develop a memory over time and can't be fully recharged unless
they are fully discharged occasionally.

This is (almost) a myth. The Ni-Cad memory phenomenon
does exist, but I can almost promise that no-one
reading this has ever experienced it.

I am sorry but you are not entirly correct.

Proven many many times and easy to repeat.
Take two brand new and identical radio controlled racing cars.
FULLY charge and discharge the nicads of one of the cars ten times.
Randomly and gently cycle the nicads of the other car ten times.
Race the cars.

Fully charged/discharged car WILL win.
Not only will the car win a short sprint race... It will also win an
endurance race.





What you are seeing has nothing to do with "memory effect".
A new nicad cell needs to be exercised several times to bring it up to
its full capacity. The capacity as to charge / discharge cycles is
sort of a bell shaped curve. Brand new not as much, after several
charge discharge cycles the capacity peaks, then it starts declining
with more charge discharge cycles.

When discharging them you should never discharge them below about 1
volt per cell. Doing so you run the risk of a cell being reverse
charged and that is the kiss of death for that cell.

Also nicad's don't like to be float charged like a lead acid battery.
A lead acid battery is as happy as can be when it is properly float
charged. A nicad is not. It will kill them. A nicad is not the proper
battery type for standby power.

Don't let a nicad get too hot when charging as that will cause the
cell to vent. Once a cell vents it is pretty much history.

By the way, there is no such thing as "memory effect". The very early
ni cad cells had sort of that problem but it does not exist in modern
cells.

Regards
Gary