Samlex Europe PST-300S-12E, Owner'S Manual

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seCtIOn 7 | General Information on lead Acid
Batteries
tABLe 7.2: DiScHARGe cURRent RAteS - “c-RAteS” (continued from Previous page)
Hours of discharge time “t” till
the “end Point Voltage”
"c-Rate" Discharge current in Amps =
capacity "c" in Ah
÷
Discharge time
"t" in Hrs.
example of c-Rate
Discharge currents
for 100 Ah battery
8 Hrs. (UPS application) C/8 or 0.125C 12.5A
10 Hrs. (Telecom application) C/10 or 0.1C 10A
20 Hrs. (Automotive application) C/20 or 0.05C 5A
100 Hrs. C/100 or 0.01C 1A
note:
When a battery is discharged over a shorter time, its specified “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.
Lead-Acid Battery Chart - 80˚F / 26.7˚C
Battery V
oltage in VDC
Battery State of Charge in Percent (%)
0 10 20 30 40 50 60 70 80 90 100 110 120 130
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
C/5
C/40
C/20
C/10
DISCHARGE
CHARGE
C/20
C/3
C/5
C/10
C/100
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
24V 12V
Fig. 7.1: Charging / Discharging Curves for 12V Lead Acid Battery
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