Page - 146 - in Emerging Technologies for Electric and Hybrid Vehicles
Image of the Page - 146 -
Text of the Page - 146 -
Energies 2017,10, 1503
2.2.DataAcquisitionandSOCEstimationwithSelf-InitializationCapability
During the system runningprocess,manyparameters, such as the cell voltage, temperature,
packvoltageandcurrent,mustbecollected inreal-time. Thestatusof thebatterypack, suchasSOC,
is requiredforcontinuous faultdiagnosis. Therefore, theaccuracyof theSOCestimation iscritical to
thesystemperformance.Ahigh-accuracydata-acquisitionmethodusingtheLTC6804 isselectedas
ananalog-to-digital converter tomonitor thebatterypack. It canmeasure thebatterycellswitha total
measurement errorof less than1.2mV.Themeasurement range from0 to5Vmakes theLTC6804
suitable for theLIBapplication,as itdoesnotconsumemuchpower. Thespeedof thedataacquisition
is fastenoughwiththe12-cellvoltages thataresampledat290μs.However, lowerdata-acquisition
ratescanbeusedforhighernoisereduction. Theconfigurationof thishardwaremodulecanbeseen in
Figure2. Theprecisionof theLTC6804wasaround0.3%.However, theoverall systemaccuracycan
beaffectedby theprint circuitboard (PCB)design. Nevertheless, theprecision targetof6%canbe
obtainedbycontinuouscalibrationfor thecaseofa lower-currentapplication.
Figure2.Hardwareconfigurationofdata-acquisitionmoduleofbatterycells (RC:resistorcapacitor,
SPI:SerialPeripheral Interface).
The releasable capacity (Creleasable) of an operatingbattery is the released capacitywhen it is
completelydischarged. TheSOCisdefinedas thepercentageof thereleasablecapacityrelative to the
battery-ratedcapacity (Crated),givenas follows:
SOC=Creleaseable/Crated×100%. (1)
Afullychargedbatteryhas themaximal releasablecapacity (Cmax),whichcanbedifferent from
the rated capacity. In general, Cmax declines as time increases. Hence, theCmax can be used for
evaluatingthestate-of-health (SOH)ofabattery:
SOH=Cmax/Crated×100%. (2)
Whenabattery isdischarging, thedepthofdischarge (DOD)canbedefinedas thepercentageof
thecapacity thathasbeendischarged(Creleased) relative toCrated:
DOD=Creleased/Crated×100%. (3)
146
Emerging Technologies for Electric and Hybrid Vehicles
- Title
- Emerging Technologies for Electric and Hybrid Vehicles
- Editor
- MDPI
- Location
- Basel
- Date
- 2017
- Language
- English
- License
- CC BY-NC-ND 4.0
- ISBN
- 978-3-03897-191-7
- Size
- 17.0 x 24.4 cm
- Pages
- 376
- Keywords
- electric vehicle, plug-in hybrid electric vehicle (PHEV), energy sources, energy management strategy, energy-storage system, charging technologies, control algorithms, battery, operating scenario, wireless power transfer (WPT)
- Category
- Technik