......Yes, it does exist. And, yes, your batteries could possibly
have the effects of it. It's the memory effect. The term "memory" basically
is described as the battery "remembers" its usual discharge point and superficially
"needs" a charge whenever it hits that point. In other words, if you have
a NiCd that always gets discharged to only 50% of its capacity, it will eventually
not run below that 50% mark if you ever wanted to discharge it to a lower
point. Many people who do not know about this effect just throw away the battery
because they think it is dead. More than likely, the battery can revived providing
that the battery isn't completely damaged (i.e. from years of memory buildup).
The most simple way to get rid of memory is to discharge the battery to 1.0
volts per cell (VPC) on a minimal load, and then charge it fully. Repeat this
procedure until you notice the battery lasting longer and longer on the drain,
until it holds its correct capacity and not the "memorized" one. Unfortunately,
unless you have good equipment, it is hard to discharge to 1.0 VPC without
accidentally "reversing" a cell.
Now, if you were only working on one cell at
a time, discharging to 1.0 VPC would be easy, but most batteries nowadays
for cellular phones and such are multiple cells in a plastic case. This makes
it hard to get every cell to 1.0 VPC. No batteries are created equal, and
what will most likely happen in a multi-cell battery is that one or more of
the cells will "reverse" because they are weaker than the other cells. The
reversed cell begins to accept a "backwards" charge from the other better
charged cells around it. This is really bad for a battery if you don't catch
it, because chances are it won't charge again while in the pack. If you are
going to discharge a pack and you cannot open it to test individual cell voltages,
please discharge to approximately 1.2 VPC. This will help prevent reversing
cells. If you do reverse a cell and can access each individual cell, I have
found that giving that cell about 4.5 volts (up to 1 A current) in the right
direction, it will probably set itself straight. Measure the voltage of the
cell after the "shock" charge. If it doesn't improve, try again. If you are
still unsuccessful, try a higher voltage. I've needed 9 volts in some cases
to get a cell working again. Once you get the cell at > 1.2 volts, immediately
put the pack on charge now so that battery won't have time to reverse again.
Charge the pack fully for 24 hours on a trickle charge to make sure that the
reversed cell(s) have recovered fully. Also note that the once-reversed cell
will never be the same. It will now always be the first one to reverse in
the pack, so you might want to be aware of that when you try to discharge/cycle
it in the future. Remember this: if you treat your battery well from the beginning
by never letting it acquire memory, you won't have to worry about these weird
procedures. Also, remember that all batteries have an expected life. NiCds
have a life of approximately 1000 cycles as long as they are treated very
well. So, if your battery is really old and doesn't hold a charge anymore,
chances are it's not memory, but a tired battery. Let it retire at a recycling
center.
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Charging Camcorder Batteries
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