Canon A-1 - Manual (Page 36)

cannot be checked in the “L" position. Then
press the battery check button on the top of
the camera for two to three seconds. If,
while pressing the battery check button,
the LED on the top of the camera blinks on
and off rapidly, battery power is sufficient.
If it blinks only slowly, twice per second, for
instance, or not at all, the power level is
insufficient
and the battery should be
replaced. It should also be replaced if the
flashing frequency changes during the few
seconds
the check button is depressed,
indicating the battery is near exhaustion.
It is a good idea to carry a spare battery
when you expect to use the camera
continuously for a long time, such as on a
vacation, when you plan to take a number of
time exposures on bulb, or when the camera
is to be used in very cold conditions.
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