"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.

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

In article ,
says...

Also nicad's don't like to be float charged like a lead acid battery.

What does "float-charged" mean?

On Fri, 18 Jun 2004 17:00:22 +0100, Stefan wrote:

In article ,
says...

Also nicad's don't like to be float charged like a lead acid battery.

What does "float-charged" mean?

"Floating a battery" refers to keeping a constant voltage charge on
the battery that is just high enough to replace the natural losses in
the battery. This is typically done with lead acid batteries that are
to be maintained at peak charge but not used for long periods.

A fully charged 12 volt lead acid battery has a voltage of around 12.7
volts. It will slowly discharge itself with no load on it if left
alone.
If a constant 13.3 to 13.6 volts (depending on temperature) charge is
left on the battery it will replace the self discharge energy of the
battery. This voltage can be left on the battery indefinitely and will
not harm the battery. Any higher charge voltage, only by a few tenths
of a volt, for long periods will harm the battery.

When initially charging the battery the voltage needs to be at around
14.2 volts for finishing the charge. Some gassing of the battery needs
to take place in the final phase of charging, slight overcharging, in
order to properly top off the cells. Then switch to the float voltage
13.3 volts to maintain.

Regards
Gary