Samlexpower PST-15S-12E Owner's manual - Section 7 |
18 | SAMLEX AMERICA INC.
seCtIOn 7 |
General Information on Batteries for
Powering Inverters
Table7.2belowgivessomeexamplesofC-Ratespecificationsandapplications:
tABLe 7.2: DiScHARGe cURRent RAteS - “c-RAteS”
Hoursofdischargetime“T”
till the “End Point Voltage”
C-RateDischargeCurrentinAmps
ExampleofC-Rate
DischargeCurrents
for100Ahbattery
fraction
Decimal
Subscript
0.5Hrs.
2C
2C
2C
200A
1Hrs.
1C
1C
1C
100A
5Hrs.
C/5
0.2C
C5
20A
8Hrs.
(UPSapplication)
C/8
0.125C
C8
12.5A
10Hrs.
(Telecomapplication)
C/10
0.1C
C10
10A
20Hrs.
(Automotiveapplication)
C/20
0.05C
C20
5A
100Hrs.
C/100
0.01C
C100
1A
note: Whenabatteryisdischargedoverashortertime,itsspecified“C-Rate”dis-
chargecurrentwillbehigher.forexample,the“C-Rate”dischargecurrentat5Hour
dischargeperiodi.e.0.2C/C5/C/5Ampswillbe4timeshigherthanthe“C-Rate”
dischargecurrentat20Hourdischargeperiodi.e.0.05C/C20/C/20Amps
.
charging / Discharging curves
fig.7.1(page19)showsthecharginganddischargingcharacteristicsofatypical,6cell,
12V,LeadAcidbatteryatelectrolytetemperatureof80°f(byconvention,batterydata
isnormallypresentedat80°f).Thecurvesshowthe%StateofCharge(X-axis)versus
terminalvoltage(Y-axis)duringcharginganddischargingatdifferentC-Rates.for24V
battery,multiplyvoltageonY-axisby2for48Vbattery,multiplyvoltageonY-axisby4
(Please note that X-axis shows % State of charge. State of Discharge will be = 100% -
% State of Charge).Thesecurveswillbereferredtoinsubsequentexplanations.
Reduction in Usable capacity at Higher Discharge Rates –
typical in inverter Application
Asstatedabove,theratedcapacityofthebatteryinAHisnormallyapplicableatadis-
chargerateof20Hours.Asthedischargerateisincreasedasincaseswheretheinverters
aredrivinghighercapacityloads,theusablecapacityreducesdueto“PeukertEffect”.
ThisrelationshipisnotlinearbutismoreorlessaccordingtotheTable7.3(page19).
Fig. 7.1: Charging / Discharging Curves for 12 V Lead Acid Battery