Manual

20
T
o avoid over-voltage, periodically check battery voltage with a
calibrated digital voltmeter. If an over-voltage is recorded, check and
readjust the rectifier and/or panel meter calibration as necessary. Place
the battery at the recommended float charging voltage as soon as
possible. Restoring the proper float voltage will preclude further dam-
age caused by charging at an over-voltage b
ut it cannot reverse dam-
age that has already been sustained by the battery.
CAUTION
Liberty Series 1000 batteries produce virtually no gas
emissions during normal operation. However, potentially
explosive gases may be released under abnormal operating
conditions or initial/equalize charge. Provide adequate
ventilation so hydrogen gas accumulation in the battery area
does not exceed one percent. Do not smoke
, use open flame
or create sparks near battery.
2.4 Voltmeter calibration
Panel voltmeters used in conjunction with float charging systems
should be kept in accur
ate calibr
ation by checking with a kno
wn
standard per the man
uf
acturer’s recommendations. Alw
ays measure
battery voltage at the battery terminals and compare the reading with
the panel meter to eliminate the effect of line drop between the batter
y
and connected system or charger. Battery voltage should always be
measured with a digital voltmeter with at least a 3
1
⁄2-digit display and a
minim
um accuracy of 0.25 percent. Battery voltage must be measured
at the battery, not at the system connection. This type of instrumenta-
tion is also particularly useful in recording individual cell potentials.
SECTION 3 - GENERAL INFORMA
TION AND MAINTENANCE
3.1 Performance characteristics
Batter
y performance at a given discharge rate is related to the internal
resistance of the cells and the external resistance of the conductors
connecting the cells
.
Aging increases internal resistance that results in
greater voltage drop, or losses. The effects of aging have the greatest
impact on high r
ate performance. A battery whose resistance has
increased b
y 10%, f
or e
xample
, when discharged at its 8-hour r
ate will
experience a loss of approximately 10% of its reserve capacity or
pro
vide only 7.2 hours of support. But the same battery discharged at
its 15 min
ute r
ate will e
xper
ience a loss of approximately 20% capaci-
ty and provide only 12 minutes of support to its final voltage. Internal
cell resistance is provided in Table 2, Part 1 of this manual.
Typically during the last half of the battery service life, performance
will begin to fall slowly at first, then at an increasing rate. Lead-acid
batteries have reached the end of their useful life when performance
has fallen to 80 percent of published ratings.
Note: Frequent charge/discharge cycles accelerate battery aging and
performance degradation.
To insure adequate performance it is recommended that a battery be
siz
ed with additional margin f
or oper
ation at minimum expected tem-
perature and for loss of capacity as the battery ages.