energy institute battery research group
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ENERGY INSTITUTE Battery Research Group. Analysis of Overcharge & Overdischarge Characteristics and Failure Detection of Li – ion Polymer Batteries Cem Kaypmaz 2008 İstanbul. Advanced Batteries. - PowerPoint PPT PresentationTRANSCRIPT
ENERGY INSTITUTEENERGY INSTITUTEBattery Research GroupBattery Research Group
Analysis of Overcharge & Overdischarge Characteristics and Failure Detection of Li – ion Polymer Batteries
Cem Kaypmaz
2008
İstanbul
Advanced Batteries
Having a Battery Management System (BMS) integrated with cells is necessary and “State Deterimation”, is a critical issue.
• The in-situ characterization of a battery is an interest for the battery manufacturers, suppliers and the third party users.
• Independent from the battery chemistry either primary or secondary, batteries are designed to perform an application specific usage.
• Studies are focused on, Telecommunication, Aerospace, Advanced Electrified Vehicles (EV, HEV, PHEV) and most Military energy storage systems.
Battery State : Aging ?
Ref: Jossen et al, 2005
Battery State
State of Charge State of Health
Battery State
Reversible Changes Irreversible Changes
- Effective Capacity- Internal Resistance- Open Circut Voltage- Gas Production
SoC State of Charge (SoC):
• (remaining capacity) / (capacity of fully charged battery)
• (Cn – Qb) / Cn
Cn: nominal capacity
Qb: net dicharged charge from a battery since the last SoC FULL
1 > SoC > 0
100% > SoC > 0%
SoH State of Health (SoH):
• (measured capacity) / (rated capacity)
• Cm / Cn
Cm: measured capacityCn: nominal capacity
1 > SoH > 0As per definition, a battery is at its end of lifetime at SoH
of 0.8 . (Ref: Rand et al, 2004)
SoF State of Function (SoF):
• Case variable
• User (or designer) defined
• May differ according to the operating conditions
Failure Modes - I For many applications and battery types, failure modes of a
battery could be listed and summarized as follows:
• A certain loss of effective capacity loss of active material, loss of conductivity in active mass
• Increase in internal resistance resulting active power loss electrolyte loss,loss of active surface
Failure Modes - II
• Increase in self discharge dendrites between the plates, poisoning of the electrolyte
• Internal short circuitformation of dendrites,
• Cell open circuit behavior grid corrosion, pasivation
Battery State: Conventional...
State of Charge (SoC)
State of Health (SoH)
State of Function (SoF)
FailureSpace
OperationalArea
Li- ion Polymer Cells
KOKAM SLPB 526495 Li-ion polymer Typical Capacity 3.3AhNominal Voltage 3.7V Life > 500cycles
(Ref: KOKAM data sheet, 2008)
4 cells : Cycling Tests
8 cells: Overcharge Tests
8 cells: Overdischarge Tests
Experimental Setup
Battery Test System (Cycler)
8 channel,
20V, 3A
Frequency Analyser (P/G)
1 Mhz-10μHzs
10V, 20A power booster
Impedance Spectroscopy
Changing the frequency of the excitation current gives the ability to detect different battery kinetics.
Ref: Barsoukov et al, 2005).
The Model
• L: The inductive behavior (L) at high frequencies (4-5kHz)
• RΩ: Pure ohmic resistance of the cell (2-3 kHz)
• Rsei and Csei : The solid electrolyte interface (sei), a pasivation layer occurring on the anode (2kHz-20Hz)
• Rct and Cdl : the charge transfer resistance and the double layer capacity (2Hz-100mHz).
• ZW: Warburg Impedance, the diffusion behavior of the battery (50mHz to 5 mHz)
• EMF: is the direct voltage produced inside the battery (Gerschler et al, 2008).
L
Csei
RΩ
EMFRsei
Cdl
Rct
-
+ZW
Tests The tests are planned to create abnormal conditions for the cells both in charge and discharge process. Normal operation voltage range of these cells declared by the manufacturer 2,7V – 4,2V and 3.3 Ah.
For “failure creation” these limits were passed and the cells were forced to failure.
• Overcharge Test (OCT) • Overdischarge Tests (ODT)
Also Cycling Tests (CT) was performed in order to follow up “normal” conditions and parameter changes.
Test Procedures
Cycling Test Procedure Overdicharge Test Procedure
Overcharge Test Procedure
Balancing (OCT) Test Procedure
Test Results After 40 Cycle Procedure
-5
0
5
10
15
15 20 25 30 35 40 45
Z re [mohm]
Z im
[m
oh
m]
ω
I
II
III
L
C1
R0
EMFR1
-
+ZW
Test ResultsAfter 3 hours of Overcharge Procedure
-10
0
10
20
30
40
50
60
20 30 40 50 60 70 80 90 100 110 120
Z re [mohm]
Z i
m [
mo
hm
]
ω
I
II
III
IV
V
L
C1
R0
EMFR1
C2
R2
-
+ZW
Test Results
Nyquist Plots for Different Test Procedures
-10
0
10
20
30
40
50
0 20 40 60 80 100 120 140
Z re [mohm]
Z im
[moh
m]
CT ODT OCT
ω
Acknowledgements