HP -65 Owner's Handbook Manual page 93

NOTE: If you use your HP-65 extensively in field work or
during travel, you may want to order the HP 82004A Bat-
tery Holder and Pack, consisting of a battery charging
attachment and spare battery pack. This enables you to
charge one pack while using the other.
Temporary degradation, peculiar to nickel-cadmium batteries,
may cause a decrease in the operating period of the battery pack.
Should this happen, turn the HP-65 on for at least 5 hours to
completely discharge the battery pack. Then, put it on charge
for at least 14 hours. This procedure should correct the tem-
porary degradation.
If the battery pack won't hold a charge, it may be defective. If
the warranty is in effect, return the pack to Hewlett-Packard ac-
cording to the shipping instructions previously discussed. If the
battery pack is out of warranty, use the Accessory Order Form
provided with your HP-65 to order a replacement.
Magnetic Cards
Protecting a Card
To protect a card containing a stored program, clip the notch
already there with scissors as shown below.
Clip here
Not here — you could lose part of the program.
Care and Maintenance
Try to keep your cards as clean and free of oil, grease, and dirt
as possible. Dirty cards can only degrade the performance of
your card reader. Cards may be cleaned with alcohol and/or
with a soft damp cloth.