Effects Of Overcharging The Battery; Using Other Battery Chargers; Memory" Effects - Teledyne 913 Installation And Operation Manual

2.2.4 Effects of Overcharging
the Battery
2.2.5 Using Other Battery
Chargers

2.2.6 "Memory" Effects

We suggest you discontinue the use of "old" batteries. Rapid
self-discharge is often the actual cause of unreliability in older
batteries, not diminished capacity. The manufacturer of the cells
used in the Isco battery considers end-of-life to have occurred
when battery capacity has dropped to 80% of the rating for new
cells.
Finally, if you cannot return the battery to service immediately
or don't know the charge condition, simply "top off " the charge
for a few hours.
Overcharging the nickel-cadmium battery causes the cells to
heat up. Over time this heating breaks down the separator
material used between the plates inside the cells, encouraging
the growth of the crystalline whiskers, causing shorts. Prolonged
overcharging will shorten the life of the cells; try to avoid it.
Teledyne Isco does not recommend the use of chargers designed
for lead-acid batteries, such as automotive battery chargers. The
open-circuit voltage of lead-acid chargers is generally not high
enough to fully charge a nickel-cadmium battery, and these
chargers are usually not current-regulated. Neither does
Teledyne Isco recommend using chargers intended for other
types of nickel-cadmium batteries, especially the so-called
"fast-charge" types. These chargers are designed for use only
with compatible "fast-charge" cells and can charge the proper
batteries in as little as one hour (1.0 "C"). Isco batteries use
"standard" cells intended for charging at 400 mA (0.1 "C") for 15
to 18 hours. Chargers that provide more current than this may
cause overheating and that may force the safety vents to open,
releasing water. You cannot replace this water.
Chargers that deliver too little current to the batteries may
never charge them to full capacity, and may themselves be
damaged from the overload. Do not attempt to use any other
charging apparatus without an accurate digital multimeter to
monitor the charging current. If the charger delivers more than
600 mA, Teledyne Isco recommends you do not use it. If it
delivers less than 100 mA, the charging period becomes too long.
Even then the battery may never recharge completely. Be sure
of proper polarity before connecting any other charging
apparatus! If you use an Isco Power Pack, you can overcharge
the battery occasionally with little loss of capacity. However, you
should avoid chronic or prolonged overcharging. Again, return
the battery to service promptly.
For a long time, people believed that nickel-cadmium batteries
were subject to "memory" effects, and that a complete charge/dis-
charge cycle (exercising the battery) was necessary to maintain
battery capacity. "Memory" is the characteristic a battery may
develop of appearing to have lost some of its capacity after a few
shallow discharges.
The battery will only discharge to the same shallow point. It is
now known that the memory effect is not a problem with Isco
equipment under normal operating conditions, because most Isco
Power Products Guide
Section 2 Batteries
2-7