How healthy is your sealed VRLA battery? Since a sealed
VRLA battery is sealed – and the sealing caps are never
removed – you won’t be able to check the state of the
charge by the old hydrometer-and-specific-gravity test.
Rather, use a voltmeter or multimeter to measure DC volt-
age. It should be of class 1 accuracy or better. Some
basics to keep in mind:
●
Check voltage using a voltmeter. Readings for a
charged, newly-activated battery should be 12.8v
or higher after the battery is charged and sits for
at least 1 - 2 hours. If less, it needs an
additional charge.
●
The graph top right shows open circuit characteristics
of the sealed VRLA battery after end of charging
using a constant current charger set to the standard
current of the specific battery. As shown, the open
circuit voltage is stabilizing 30 minutes after end
of charge.
Therefore, to determine the state of charge and the
health of the battery, measure the open circuit
voltage 1 hour after end of charge.
●
For a battery that has been in use, refer to the graph
bottom right to determine state of charge from
open circuit voltage.
Measuring Voltage
Relation between State of Charge
and Open Circuit Voltage
14
13
12
11
10
100 75 50 25 0
State of Charge (%)
Open Circuit Voltage (v)
Ambient Temperature
32-104°F (0~40°C)
27
Open Circuit Voltage Characteristics
after End of Charge
18
17
16
15
14
13
12
11
10
0 102035405060
Elapsed Time (minutes)
Terminal Voltage (v)
Ambient Temperature
77°F (25°C)
Charge Open Circuit
POINTS TO REMEMBER
❐ Use a voltmeter to determine state of charge. Because sealing caps are
never removed, you can’t test specific gravity.
❐ Don’t use a quick charge for initial activation.
❐ A battery that has just been activated or charged needs to stabilize
1 hour for an accurate voltage reading.
5
SECTION
Sealed VRLA
Batteries
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