Manual
13
745-680-B8-002, Rev. B
3.0 Storage
Open circuit
When a battery is stored in an open circuit, two major things occur:
Sulfate leaves the electrolyte and reacts with the plates, causing a reduction in the charge state 1.
of the battery.
Grid corrosion accelerates, especially when the open circuit voltage of the battery is allowed to go 2.
below 2.05Vpc.
The state of charge of lead acid batteries slowly decreases in an open circuit due to self-discharge.
In SMU-F batteries, the rate of self-discharge is about 2–3% per month at 77ºF (25ºC). During
prolonged storage it is necessary to boost-charge the battery at least every 6 months to maintain
a fully charged condition of the battery (see Section 2.2). Excessive open circuit storage of any
lead acid battery without recharge will result in a permanent loss of capacity. When stored at higher
temperatures, the boost interval should be more frequent. Keep the open circuit voltage (measured
in a fully rested state of at least 16 hours) at or above 2.05Vpc to minimize the amount of irreversible
grid corrosion.
Fig. 2-1, Recharge Time and Capacity Restored as a Function of Current Limit
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
110%
0246810121416
Hours
Capacity
0.1C
10
0.1C
5
0.2C
5
2.2 Recharge Following Discharge
Using a current limit of 0.1 C
10
, it takes approximately 9 hours to restore 80% of the discharge, and 11
hours to restore 90%. This can be compared to a current limit of 0.25 C
10
, whereby 80% is returned in
approximately 4 hours, and 90% within 5 hours.
NOTE:
While less charger (rectier) amps means a longer recharge time, too many charger (rectier) amps can
damage the battery.
Storage Temperature ºF (ºC) Boost Interval
77 (25) 6 Months
95 (35) 3 Months
113 (45) 1 Month
Table 3-1, Boost Charge Intervals