Alpha Technologies AlphaCell SMU-HR - Manual (Page 13)

13 745-680-B2-002, Rev. B
2.2 Recharge Following Discharge, continued
Using a current limit of 0.1 C10, 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 C10,
whereby 80% is returned in approximately 4 hours, and 90% within 5 hours.
3.0 Storage
Open circuit
When a battery is stored in an open circuit, two major things occur:
1 Sulfate leaves the electrolyte and reacts with the plates, causing a reduction in the charge
state of the battery.
2. Grid corrosion accelerates, especially when the open circuit voltage of the battery is allowed
to go below 2.05Vpc.
The state of charge of lead acid batteries slowly decreases in an open circuit due to self-discharge. In
SMU-HR batteries, the rate of self-discharge is about 23% per month at 77F (25C). 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
While less charger (rectifier) amps means a longer recharge time, too many charger (rectifier) amps can
damage the battery.
NOTE:
Table 3-1, Boost Charge Intervals
0.1C
10
0.1C
5
0.2C
5
0 2 4 6 8 10 12 14 16
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
110%
Storage Temperature °F (°C) Boost Interval
77 (25) 6 Months
95 (35) 3 Months
113 (45) 1 Month
Hours
Capacity