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Appendix
Model 415E
MAINTENANCE OF THE RECHARGEABLE NICKEL CADMIUM BATTERY
The maintenance of the rechargeable Nickel Cadmium
battery poses two problems, both of which pertain to
recharging the battery.
The first problem concerns damage to the battery be¬
cause of improper maintenance. Damage during oper¬
ation and storage will reduce the number of charging
cycles and therefore the life of the battery.
The second problem concerns that of thermal runaway.
As the Nickel Cadmium battery heats due to the charging
current, the battery terminal voltage drops.
The
charging current will then increase if the recharging
circuit consists of a constant voltage source.
This
thermal runaway will result in destruction of the bat¬
tery. This problem, however, is alleviated in Hewlett-
Packard instruments because a constant current source
provides battery recharge.
Maintenance of the Nickel Cadmium battery can be
summarized with several DO NOT's.
1. Do not allow the battery to discharge below 6 volts
per 5 cell battery (1.2 volts per cell). This will
prevent reverse charging of one or more cells.
2. Do not fast charge for periods exceeding 75 hours
because excessive heat generaged may shorten
battery life. Typical charging rates are a trickle
charge of 4 mA to 7 mA and a fast charge rate
of 16 mA to 18 mA, where applicable. The bat¬
tery may be charged at a trickle rate indefinitely.
3. Do not charge the batteries in an environment
with temperatures above 95°F (35 "C) or below
32°F (0°C). Whenever possible, charge the bat¬
tery at moderate temperatures (70 °F ilO^F,
21°C ±5.6°C).
Operation of the battery in the
same moderate temperatures as for battery
charging will provide maximum performance.
4. Do not store the battery at temperatures above
122 °F (50°C) or below -4°F (-20°C). Prolonged
storage (90 days under ideal conditions) may re¬
quire three to five charge-discharge cycles to
reach full capacity.
5. Do not short-circuit the battery because the ex¬
ceedingly low internal resistance will allow dis¬
charge at extremely high current levels.
This
will result in battery damage.
1-2
02152-4
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