User manual

Just as every 8°C rise in operating temperature cuts the
battery’s life expectancy in half, so does every 8°C
increase in ambient temperature reduce the storage life
of a battery by 50%. Conversely, a reduction in storage
temperature will have the reverse effect by increasing
the allowable storage time.
2.11 Open circuit voltage (OCV) and state of charge
(SOC)
Since most batteries are subject to some kind of storage,
it is important for the user to have some method of
accurately estimating the battery capacity after it has
been in storage.
Figure 2.11.1: Open circuit voltage and state of charge
Although efforts should be made to ensure that batteries
are stored in temperature-controlled environments, a
freshening charge should be applied once every twenty-
four (24) months or when the open-circuit voltage (OCV)
reading drops to 12V, whichever comes first. As shown
in Figure 2.11.1, 12V corresponds to a 35% state of
charge (SOC).
The battery may be permanently
damaged if the OCV is allowed to drop below 11.90V
.
Figure 2.11.1 shows the OCV and corresponding SOC for
a Genesis battery. An OCV of 12.84V or more indicates a
battery at 100% SOC. The figure is accurate to within
20% of the true SOC of the battery
if the battery has not
been charged OR discharged in the 24 hours preceding
the voltage measurement
. The accuracy improves to 5%
if the period of inactivity before the voltage
measurement is 5 days.
Capacity loss during storage is an important
consideration, particularly in applications where
performance loss due to storage is unacceptable.
However, knowing how much charge is remaining in the
battery at any point in its storage life is equally
important as the battery must be maintained at a
minimum charge level in order to prevent permanent
damage. Figure 2.11.2 shows the relationship between
storage time and remaining capacity at 25ºC, 45ºC and
65ºC.
Figure 2.11.2: Storage capacity at temperatures
2.12 Procedure to recover overdischarged batteries
There may be instances when a Genesis
®
battery is
overdischarged to the point where a standard charger is
unable to fully recharge the battery. In such cases, the
following procedure may help recover the affected
battery.
1. Bring the battery to room temperature (25°C).
2. Measure the OCV. Continue to step 3 if it is at least
12V; otherwise terminate the procedure and reject the
battery.
3. Charge the battery using a 0.05C
10 constant current for
24 hours. The charger should be capable of providing
a driving voltage as high as 36V. Monitor the battery
temperature;
discontinue charging if the battery
temperature rises above 45ºC
.
4. Allow the charged battery to stand on open circuit for
a minimum of 1 hour before proceeding to Step 5.
5. Perform a capacity test on the battery and record the
amp-hours delivered. The longer the discharge the
more reliable the result. This is Cycle 1.
6. Repeat steps (3) to (5). The capacity returned in step 5
is now Cycle 2. If Cycle 2 capacity is greater than Cycle
1 capacity proceed to step 7; otherwise reject the
battery.
7. Repeat steps (3) to (5) to get Cycle 3 capacity. Proceed
to step 8 if Cycle 3 capacity is equal to or more than
Cycle 2 capacity. Reject the battery if Cycle 3 capacity
is less than Cycle 2 capacity.
8. If Cycle 3 capacity equals or exceeds Cycle 2 capacity,
recharge the battery and put it back in service.
Open circuit storage time in weeks
Percent of 0.05C capacity
10
20
30 40
50
60 70
80
90
100
0
70
30
40
60
50
25°C
45°C
65°C
State of Charge (SOC), %
Open circuit voltage (OCV), V
10
20 30 40 50 60 70 80 90 100
13.0
12.8
12.6
12.4
12.2
12.0
11.8
11.6
12.84V or higher indicates 100% SOC
10
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