Samlex Power PST-600-12 Manuel Du Propriétaire page 20

Section 7 |
TABLE 7.2: DISCHARGE CURRENT RATES - "C-RATES" (continued from Previous page)
Hours of discharge time "T" till
the "End Point Voltage"
8 Hrs. (UPS application)
10 Hrs. (Telecom application)
20 Hrs. (Automotive application)
100 Hrs.
NOTE:
When a battery is discharged over a shorter time, its specifi ed "C-Rate" discharge current will
be higher. For example, the "C-Rate" discharge current at 5 Hour discharge period i.e. C/5 Amps will
be 4 times higher than the "C-Rate" discharge current at 20 Hour discharge period i.e. C/20 Amps.
7.7 CHARGING / DISCHARGING CURVES
Fig. 7.1 shows the charging and discharging characteristics of a typical 12V / 24V Lead Acid
battery at electrolyte temperature of 80°F / 26.7°C. The curves show the % State of Charge
(X-axis) versus terminal voltage (Y-axis) during charging and discharging at different C-Rates.
Please note that X-axis shows % State of Charge. State of Discharge will be = 100% - %
State of Charge. These curves will be referred to in the subsequent explanations.
24V 12V
33.0
32.0
31.0
30.0
29.0
28.0
27.0
26.0
25.0
24.0
23.0
22.0
21.0
20.0
19.0
18.0
Fig. 7.1: Charging / Discharging Curves for 12V Lead Acid Battery
20 | SAMLEX AMERICA INC.
General information on Lead Acid
Batteries
"C-Rate" Discharge Current in Amps =
Capacity "C" in Ah
Lead-Acid Battery Chart - 80˚F / 26.7˚C
16.5
16.0
15.5
15.0
14.5
14.0
13.5
13.0
12.5
12.0
11.5
11.0
10.5
10.0
9.5
9.0
0 10 20 30 40
Battery State of Charge in Percent (%)
÷
Discharge Time
"T" in Hrs.
C/8 or 0.125C
C/10 or 0.1C
C/20 or 0.05C
C/100 or 0.01C
CHARGE
C/100
C/20
C/10
C/5
C/3
50 60 70 80 90 100
Example of C-Rate
Discharge Currents
for 100 Ah battery
12.5A
10A
5A
1A
C/5
C/10
C/20
C/40
DISCHARGE
110 120 130