SamplexPower PST-300-12 Manuel Du Propriétaire page 18

seCtIOn 7 |
Table 7.2 below gives some examples of C-Rate specifications and applications:
tABLe 7.2: DiScHARGe cURRent RAteS - "c-RAteS"
Hours of discharge time "t"
till the "end Point Voltage"
0.5 Hrs.
1 Hrs.
5 Hrs.
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 specified "C-Rate" dis-
charge current will be higher. for example, the "C-Rate" discharge current at 5 Hour
discharge period i.e. 0.2C / C5 / C/5 Amps will be 4 times higher than the "C-Rate"
discharge current at 20 Hour discharge period i.e. 0.05C / C20 / C/20 Amps
charging / Discharging curves
fig. 7.1 (page 19) shows the charging and discharging characteristics of a typical, 6 cell,
12V, Lead Acid battery at electrolyte temperature of 80°f. The curves show the % State
of Charge (X-axis) versus terminal voltage (Y-axis) during charging and discharging
at different C-Rates. for 24V battery, multiply voltage on Y-axis by 2 for 48V battery,
multiply voltage on Y-axis by 4 (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
subsequent explanations.
Reduction in Usable capacity at Higher Discharge Rates –
typical in inverter Application
As stated above, the rated capacity of the battery in Ah is normally applicable at a dis-
charge rate of 20 Hours. As the discharge rate is increased as in cases where the inverters
are driving higher capacity loads, the usable capacity reduces due to "Peukert Effect".
This relationship is not linear but is more or less according to the Table 7.3 (page 19).
18 | SAMLEX AMERICA INC.
General Information on Batteries for
Powering Inverters
c-Rate Discharge current in Amps
Fraction
2C
1C
C/5
C/8
C/10
C/20
C/100
Decimal Subscript
2C 2C
1C 1C
0.2C C5
0.125C C8
0.1C C10
0.05C C20
0.01C C100
example of c-Rate
Discharge currents
for 100 Ah battery
200A
100A
20A
12.5A
10A
5A
1A
.