Quantcast Section IV-Valve Regulated Lead Acid Cell Batteries

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TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
charge, or a lower specific gravity between equaliz-
ing to a fully charged battery, that has been under
constant voltage of 2.15 volts per cell for approxi-
ing charges when compared with adjacent cells.
mately 1 hour or more, should be between 0.25 and
c. Charging voltage. Battery voltage should be
1.0 percent of the 8-hour rate of the battery At a
increased for a definite period of time as shown in
higher temperature, or when there has been a re-
table 14-3. The highest voltage that circuit and
cent discharge, an increase in current is required.
equipment limitations will permit should be used. A
At lower temperatures, if the battery has been sub-
continuous charge is preferable, but intermittent
ject to a higher voltage, a lower current will be
charging may be necessary to conform to working
observed which may flow temporarily in the dis-
schedules. In any case, the charge must be contin-
charge direction. If the trickle rate is consistently
ued until all cells gas freely. Raising the voltage,
less than 0.25 percent or more than 1.0 percent of
particularly to the higher values of table 14-3,
the 8-hour rate of the battery, the meter should be
should be done gradually to avoid excessive cur-
checked. A permanently connected ammeter in the
rents. After completing the equalizing charge, the
battery circuit is impracticable, because any high
charging voltage should be reduced slowly to below
discharge currents would pass through the meter in
the floating value and the ammeter should be
a reverse direction.
watched to avoid reversal of the current to the
charging source. After a few minutes, the voltage
Table 14-3. Equalizing charge
should be increased to the floating value. Do not
wait for the battery voltage and current to stabilize
Battery voltage
Battery voltage
Length of monthly
at precharge values.
per cell (volts)
for 60 cells (volts)
Charge (hours)
d. Charging current. Actual battery charging cur-
2.42 . . . . . . . . . . . . . . .
145 . . . . . . . . . . . . . . .
3 to 8
143 . . . . . . . . . . . . . . .
2.39 . . . . . . . . . . . . . . .
4 to 12
rent depends on temperature, battery age, and re-
142 . . . . . . . . . . . . . .
2.36 . . . . . . . . . . . . . . .
6to 16
cent use of the battery. Therefore, specific charging
140 . . . . . . . . . . . . . . .
8 to 24
2.33 . . . . . . . . . . . . . . .
current values cannot be given. As a general guide,
138 . . . . . . . . . . . . . . .
2.30 . . . . . . . . . . . . . . .
11 to 34
at its optimum operating temperature, current flow-
14-13. Valve-regulated cell differences.
to enhance a recombination of hydrogen and oxygen
back to water. Properly charged, there is a minimal
Valve-regulated sealed lead-acid cells are not in-
loss of evolved hydrogen and oxygen; therefore, no
stalled in transparent jars like traditional cells.
water needs to be replaced during the battery's ex-
Plates are not visible, and the electrolyte is not
pected life. Charging above the manufacturer's rec-
ommended rating will result in venting hydrogen
a. Maintenance. These batteries are neither
and oxygen from the cell and, if prolonged, will
sealed nor maintenance-free. The cell cannot be con-
cause premature failure. Gelled electrolyte cells are
sidered sealed as a pressure relief valve is provided
normally operated in a vertical orientation; how-
to open when the cell's internal pressure exceeds a
ever, some manufacturers can-produce a cell which
set limit. Once the pressure is relieved the valve
can be operated horizontally.
closes and reseals. Cell which do not reseal but leak
14-14. Charging of valve-regulated cells.
may require replacement. For this type of construc-
tion there is no need to check the electrolyte level
Charging of valve-regulated sealed lead-acid cells is
nor the specific gravity of each cell. Other battery
similar to charging of flooded cells, but the charging
maintenance requirements are still necessary, such
voltage must be monitored more closely. Normally,
as visual inspection, cleanliness, cell voltage resis-
the cells operate on float charge without the need
tance, charging, capacity testing, and others previ-
for a periodic equalizing charge. Recharge times are
ously covered. Outgassing of these batteries is low
relatively short when recharges are required. Tem-
at normal charge rates, but it can occur when there
perature compensation of the float voltage is more
is a battery or a battery charger failure. Do not fully
critical than `for flooded cells, and a temperature-
enclose cells in any manner which inhibits cooling
compensated battery charger should be utilized.
air, and do not place them in the heat flow of elec-
14-15. Temperature compensation for valve-
tronics which may occupy the same enclosure. For
regulated cells.
safety reasons these batteries require the necessary
air changes covered earlier.
Failure to temperature-compensate the float volt-
b. Types. There are two types of cells commer-
age can cause premature cell failure. The recom-
cially available: the absorbed (or starved) electro-
mended float voltage is 2.25 volts per cell at 77
degrees F (25 degrees C). The float voltage may
lyte cell and the gelled electrolyte cell. Both operate


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