Samlexpower PST-1500-12 Owner's Manual - Section 7 |
22 | SAMLEX AMERICA INC.
SAMLEX AMERICA INC. | 23
The discharge curves in fig. 7.1 show the % State of Charge versus the terminal voltage
oftypicalbatteryunderdifferentcharge/dischargecurrents,i.e.“C-Rates”andfixed
temperatureof80°F.(PleasenotethattheX-Axisofthecurvesshowsthe%ofStateof
Charge.The%ofStateofDischargewillbe100%-%StateofCharge).
7.11 LOW DC INPUT VOLTAGE ALARM IN INVERTERS
Asstatedearlier,thebuzzeralarmistriggeredwhenthevoltageattheDCinputtermi-
nals of the inverter has dropped to around 10.5V for a 12V battery (21V for 24V battery)
at C-Rate discharge current of C/5 Amps. Please note that the terminal voltage relative
toaparticularofStateDischargedecreaseswiththeriseinthevalueofthedischarge
current.Forexample,terminalvoltagesforaStateofDischargeof80%(StateofCharge
of 20%) for various discharge currents will be as given at Table 7.5 (Refer to fig 7.1 for
parameters and values shown in Table 7.5):
TABLE 7.5 TERMINAL VOLTAGE AND SOC OF LOADED BATTERY
Discharge Current:
C-Rate
Terminal Voltage at 80% State
of Discharge (20% SOC)
Terminal Voltage When Completely
Discharged (0% SOC)
12V
24V
12V
24V
C/3A
10.45V
20.9V
09.50V
19.0V
C/5 A
10.90V
21.8V
10.30V
20.6V
C/10 A
11.95V
23.9V
11.00V
22.0V
C/20 A
11.85V
23.7V
11.50V
23.0V
C/100 A
12.15V
24.3V
11.75V
23.5V
Intheexamplegivenabove,the10.5V/21.0VLowBattery/DCInputAlarmwouldtrig-
ger at around 80% discharged state (20% SOC) when the C-Rate discharge current is C/5
Amps. However, for lower C-Rate discharge current of C/10 Amps and lower, the battery
will be almost completely discharged when the alarm is sounded. Hence, if the C-Rate
discharge current is lower than C/5 Amps, the battery may have completely discharged
by the time the Low DC Input Alarm is sounded.
7.12 LOW DC INPUT VOLTAGE SHUT-DOWN IN INVERTERS
Asexplainedabove,ataround80%StateofDischargeofthebatteryatC-Ratedis-
chargecurrentofaroundC/5Amps,theLowDCInputVoltageAlarmissoundedat
around 10.5V for a 12V battery (at around 21V for 24V battery) to warn the user to
disconnect the battery to prevent further draining of the battery. If the load is not dis-
connected at this stage, the batteries will be drained further to a lower voltage and to a
completely discharged condition that is harmful for the battery and for the inverter.
Inverters are normally provided with a protection to shut down the output of the inverter
iftheDCvoltageattheinputterminalsoftheinverterdropsbelowathresholdofaround
10Vfora12Vbattery(20Vfor24Vbattery).ReferringtotheDischargeCurvesgivenin
Fig7.1,theStateofDischargeforvariousC-Ratedischargecurrentsforbatteryvoltageof
10V/20Visasfollows:(PleasenotethattheX-Axisofthecurvesshowsthe%ofStateof
Charge.The%ofStateofDischargewillbe100%-%StateofCharge):
Section 7 |
General information on Lead Acid