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Chapter 16: Practical Battery Tips
Batteries seem to have a mind of their own. Their stubborn and
unpredictable behavior has left many battery users in awkward
situations. In fact, the British Army could have lost the Falkland
War in 1982 because of uncooperative batteries. The army assumed
that a battery would always follow rigid military specifications.
Not so. When the order was given to launch the portable missiles,
nothing happened and the missiles did not fly that day. Such
battery-induced letdowns happen on a daily basis. Some are simply
a nuisance, others have serious consequences.
In this section we examine what the user can
reasonably expect from a battery. We learn how to cope with
the many moods of a battery and how to come to terms with
its limitations.
Personal Field Observations
While working with General Electric, I had the
opportunity to examine the behavior of many NiCd batteries
for two-way radios. I noticed a trend with these batteries
that was unique to NiCd. These particularities repeated themselves
in various other applications.
A certain organization continually experienced
NiCd battery failure after a relatively short service time.
Although the batteries performed at 100 percent when
new, their capacity dropped to 20 percent and below within
one year. We discovered that their two-way radios were under-utilized;
yet the batteries received a full recharge after each short
field use.
After replacing the batteries, we advised the
organization to exercise the new batteries once per month
by discharging them to one-volt-per cell with a subsequent
recharge. The first exercise took place after the batteries
had been in service for four months. At that stage, we were
anxious to find out how much the batteries had deteriorated.
Here is what we found:
On half of the batteries tested, the capacity
loss was between 25 to 30 percent; on the other half,
the losses were around 10 to 20 percent. With exercise
— and some needed recondition cycles — all batteries were
fully restored. Had maintenance been omitted for much longer,
the probability of a full recovery would have been jeopardized.
On another occasion, I noticed that two-way radios
used by construction workers experienced fewer NiCd battery
problems than those used by security guards. The construction
workers often did not turn off the radios when they put down
their hammers. As a result, the batteries got their exercise
and kept performing well until they fell apart from old age.
In many cases the batteries were held together with electrician’s tape.
In comparison, the security guards pampered their
batteries to death by giving them light duty and plenty of
recharge. These batteries still looked new when they had to
be discarded after only 12 months of service. Because
of the advanced state of memory, recondition was no longer
effective to restore these batteries.
On a further application, I studied the performance
of a two-way radio that was available with batteries of different
capacities. It soon was apparent that the smaller battery
lasted much longer, whereas the larger packs needed replacing
more often. The small battery had to work harder and received
more exercise during a daily routine.
Equipment manufacturers are aware of the weak
link — the battery. For a more reliable energy source, higher
capacity batteries are recommended. Not only are oversized
batteries bulky, heavy and expensive, they hold more residual
charge prior to recharge than smaller units. If the residual
energy is never fully consumed before a recharge, and no exercise
is applied, the nickel-based battery will eventually lose
its ability to hold charge due to memory.
On the lithium and lead-base systems, a slightly
oversized battery offers an advantage because the pack is
less stressed on deep discharges. The battery does not need
to be discharged as low for the given application. A high
residual charge before recharge is a benefit rather than a
disadvantage for these chemistries.
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