Samlexpower PST-100S-12E Owner's Manual - Section 7 |
16 | SAMLEX AMERICA INC.
SAMLEX AMERICA INC. | 17
seCtIOn 7 |
General Information on Batteries for
Powering Inverters
anelectricalconductorinonesecond.TheCapacity“C”inAhrelatestotheabilityofthe
batterytoprovideaconstantspecifiedvalueofdischargecurrent(alsocalled“C-Rate”)over
a specified time in hours before the battery reaches a specified discharged terminal voltage
(Alsocalled“EndPointVoltage”)ataspecifiedtemperatureoftheelectrolyte.Asabench-
mark,theautomotivebatteryindustryratesbatteriesata“DischargeRate”C/20Amperes
correspondingto20Hourdischargeperiod.Theratedcapacity“C”inAhinthiscasewillbe
thenumberofAmperesofcurrentthebatterycandeliverfor20Hoursat80ºf(26.7ºC)till
thevoltagedropsto1.75V/Celli.e.10.5Vfor12Vbattery,21Vfor24Vbatteryand42Vfora
48Vbattery.forexample,a100Ahbatterywilldeliver5Afor20Hours.
Rated capacity in Reserve capacity (Rc)
BatterycapacitymayalsobeexpressedasReserveCapacity(RC)inminutestypicallyfor
automotiveSLI(Starting,LightingandIgnition)batteries.Itisthetimeinminutesa
vehicle can be driven after the charging system fails. This is roughly equivalent to the
conditions after the alternator fails while the vehicle is being driven at night with the
headlights on. The battery alone must supply current to the headlights and the com-
puter/ignitionsystem.Theassumedbatteryloadisaconstantdischargecurrentof25A.
Reservecapacityisthetimeinminutesforwhichthebatterycandeliver25Amperesat
80ºf(26.7ºC)tillthevoltagedropsto1.75V/Celli.e.10.5Vfor12Vbattery,21Vfor24V
batteryand42Vfor48Vbattery.Approximaterelationshipbetweenthetwounitsis:
Capacity“C”inAh=ReserveCapacityinRCminutesx0.6
typical Battery Sizes
TheTable7.1belowshowsdetailsofsomepopularbatterysizes:
tABLe 7.1: PoPULAR BAtteRY SiZeS
Bci* Group
Battery Voltage, V
Battery capacity, Ah
27/31
12
105
4D
12
160
8D
12
225
GC2**
6
220
*BatteryCouncilInternational;**GolfCart
Specifying charging / Discharging currents: c-Rate
Electricalenergyisstoredinacell/batteryintheformofDCpower.Thevalueofthe
stored energy is related to the amount of the active materials pasted on the battery
plates,thesurfaceareaoftheplatesandtheamountofelectrolytecoveringtheplates.
Asexplainedabove,theamountofstoredelectricalenergyisalsocalledtheCapacityof
thebatteryandisdesignatedbythesymbol“C”.
ThetimeinHoursoverwhichthebatteryisdischargedtothe“EndPointVoltage”for
purposesofspecifyingAhcapacitydependsuponthetypeofapplication.Letusdenote
thisdischargetimeinhoursby“T”.Letusdenotethedischargecurrentofthebattery