10.batteries & management · 2020-04-11 · lund university / lth / iea / avo reinap / mvkf25 /...

09-APR-2020MVKF25 Hydrogen, Batteries, Fuel Cells

10.Batteries & Management Balancing, BMS, TBMS States, degradation, models

Lund University / LTH / IEA / Avo Reinap / MVKF25 / 2020-04-09 2

L10: Batteries & Management•

Energy management

–

Battery management system–

Electric

and Thermal

management

•

Battery states –

Charge (SoC), Function (SoF), Health (SoH)

–

Performance deterioration

and battery degradation•

Battery characteristics and models

•

Charging

and discharging–

Charger, rechargeable battery, Li-ion Battery

–

Self-discharge

W

W

W

W

W W

W W

https://en.wikipedia.org/wiki/Battery_management_system

https://en.wikipedia.org/wiki/Self-discharge

https://en.wikipedia.org/wiki/Battery_charger

https://en.wikipedia.org/wiki/Electric_battery

https://en.wikipedia.org/wiki/Rechargeable_battery

https://en.wikipedia.org/wiki/Lithium-ion_battery

https://en.wikipedia.org/wiki/State_of_charge

https://en.wikipedia.org/wiki/State_of_health


Guide•

Battery characteristics

and model

(Ch 1 & 2)–

Cell components

–

Electrochemical energy conversion

–

Performance characteristics

–

Electrochemical analysis methods

•

Battery control

and management

(Ch 6 & 6)

–

Energy management–

State functions

•

Battery usage

and degradation

(Ch 7)

–

Degradation mechanisms–

Degradation of Li-ion cells

–

Degradation analysis


Value chain for EV batteries

•

Not only energy management but also material usage/reusage

•

From cell realization to recycling (excluding raw materials)

•

Vehicle power (performance), energy (range) and integration (BMS)

Fig.Ref.: B. Averill, P. Eldredge, “General Chemistry: Principles, Patterns and Applications”


Energy Management vs Design

•

A cross-road of different disciplines•

Multi-dimensional (analysis) & multi-

objective (synthesis)

Construction Production

Energy Conversion

kg kW, kWh

Pack specificationPack architecture

Pack designElectrical power system

Module designElectrical distribution system

System safetyBMS design

Module CU

CELL

•Joining methods

and E, M, T criteria?

Information

Energy•

Monitoring –

measure what

is important•

Control –

keep it optimal and

constrained•

Diagnosis –

keep battery

cells healthy


Thermal

energy

management -

TBMS•

.J. Li, Z. Zhu, “Battery Thermal Management Systems of Electric Vehicles”, MSc Chalmers 2014

•

29.5/17.7 kWh

&1700/270 kg


dtdC

RE

EEEEEdtd

thambth

losses

outputinputlossesgenerationonaccumulati

1

Battery : store energy and use it ;)

CH

AR

GE

DISC

HA

RG

E

Voltage [V]

Energy [Ah]

Current [A]


Battery overview•

Parameters (of primary interest)

–

Voltage, E [V]–

Capacity, Q [Ah]

•

Models & approaches–

Mathematical: chemical process kinetics & Markov process based stochastic model

–

Electrochemical: physics based set of coupled partial differential equations connecting laws related to chemical concentration and electric current flow

–

Single particle model–

Equivalent circuit: Electric circuit consisting of RCE

Ageing modelThermal model

Electrical model


Voltage and Capacity•

Electric operation domain

–

Voltage range –

Vmin

-Vmax

–

State of Charge –

SOC•

Depth of discharge DOD=100%-SOC

–

Voltage range –

min

-max

•

Open circuit voltage OCV(SOC, )

•

Internal resistance R(SOC,I,) results voltage drop and power losses

Voltage [V]

Capacity [Ah]

Vmax

VminQmin

Qmax

%100nomQtQtSOC


More voltage and more capacity•

Series → increase voltage

•

Cells in parallel → increase capacity → unequal voltage drives current

•

The largest safely drawn charge is the one that is stored in the weakest cell

•

Purpose of BMS–

Indentify state of charge SOC

–

Maximize capacity –

Provide safe function

Voltage [V]

Capacity [Ah]

BM

S


Battery control and BMS•

Energy management

–

Electric

operation range

– energy

balancing

for

better

usage–

Thermal

operation range

–

Keep temperature & use little energy for operation

•

Battery cell-module-pack development and control is supported buy models

–

From models in physics (FEM) towards datasheet and equivalent circuit modeling

–

from

component physics towards system realisation


Battery modeling A•

Simple approach @ limited data, parameters are independent of SOC, current

(rate) and

temperature•

Cell voltage

U=Eo

-Ro

I where Ro

is internal resistance and Eo

is open circuit voltage (OCV)

•

Heating power Ploss

=(Ro

I)2

only

Ohmic

losses•

Transient temperature

rise

=Ploss

Rh

(1-e-t/RhC

h

)


Battery modelling B

Heat generation

model

Cell Electrical

model

Cell Thermal model

VtVoc

SoC

I* ϑa

Qϑ

•

Simulink SimPowerSystem

•

Generic

dynamic model

•

Pre

characterised charging/discharging

characteristics


Electric equivalent circuit

•

Electrolyte resistance –

causes resistive voltage drop at current flow

•

Diffusion and surface reaction –

results the voltage transient(s) at current step

R1

C1

R2

C2

R0

E=Uoc(Vsoc)

Ccap

Rsdc

Ibat Ibat

VsocBattery Lifetime

Voltage-Current Characteristics


Step response


Frequency response


Electrochemical force and cell

•

Chemical reaction = two half-reactions: oxidation+reduction=redox

–

Side reactions due to thermal loads, pressure?

•

Active, electrodes, non-active, the rest including electrolyte, components

B. Averill, P. Eldredge, “General Chemistry: Principles, Patterns and Applications”


Principles, definitions, realizationsLEFT:

Negative electrode

RIGHT:Positive electrode

OxRedln0 nF

RTEEEE leftrightcell


Keywords to previous slide•

Electrochemical energy conversion

–

Ch → E: Galvanic, Oxidation → loss of electrons → discharging

–

E → Ch: Electrolytic, Reduction → gain of electrons → charging

•

Nernst equation•

Electrode domain

–

μm-scale

•

From left to right = negative electrode positive electrode and boundaries for different domains in between

CH 1 : The electrochemical cell


Energy and power•

Specific energy originates from material chemistry

–

Capacity capability

•

Specific power is related to material physics and production

–

Internal power losses and thermal constrains –

durability and safety

p. 40 & 129


Cell voltage

cell

negcctposcct

negposcell

iR

EEE

•

Activation polarization – charge transfer (ηct

) from electrode surface

•

Concentration polarization – caused by concentration (ηc

) differences between electrode and electrolyte due to ionic conductivity and transport properties

•

Ohmic

polarization –

IR drop proportional to current

p. 34


Voltage hysteresis

cha

disE

cha

disQ

t

t

dttItV

dttItV

QQ

dttIQ

tSOCtSOC

0

10

•

Charge-Discharge profile•

Delay in chemical and electrochemical reactions, causes difference between charging and discharging voltages

•

Voltage hysteresis, ΔE, may

increase

with charge

and discharge rate

p. 34


Charge and Discharge rates•

A C-rate is a measure of the rate at which a battery is discharged relative to its maximum capacity.

•

A 1C rate means that the discharge current will discharge the entire battery in 1 hour.

•

Practical capacity is defined as the current density passing through the cell until the cut-off voltage is reached

•

How C-rate affect cell performance

p. 37


Capacity

Ageing model

Electrical model

current Thermal model

power

temperaturevoltage

DoD SoH

•

Specific capacity [Ah/kg] of used electrochemical active material

•

Capacity fade due to loss of recyclable Lithium and SEI build up

p. 37 & 197


Cyclic voltammetry

•

Galvanostatic

cycling –

voltage response at constant current –

study the cell capacity and degradation

•

Potentiostatic

cycling –

holding voltage constant and decline the current

•

Cyclic voltametry

for electrode reaction response at linearly changed voltage resulting current peaks

W

1.7.2 & 7.3.3

https://en.wikipedia.org/wiki/Voltammetry


Electrochemical impedance spectroscopy

•

Frequency response of battery•

Detect changes of the interfacial properties of the electrode –

charge transfer impedance (R||C)

W

1.7.3 & 7.3.2

https://en.wikipedia.org/wiki/Dielectric_spectroscopy


EIS battery testing•

Electrochemical

dynamic

response–

Respons is related

to ion-

current/diffusion

rate in the cell–

Slower

response

for weaker

batteries

•

Characterization–

LF dubbed diffusion–

MF charge transfer–

HF migration

•

Batteries with faded capacity suffer from low charge transfer and slow active Li-ion diffusion.

http://batteryuniversity.com/learn/article/testing_lithium_based_batteries

http://batteryuniversity.com/learn/article/testing_lithium_based_batteries


Battery performance degradation

•

Degradation –

deterioration

of useful capacity and power capabilities

•

Identification of physical and chemical processes behind degradation mechanisms . Origins related to technology and usage.

•

SoH

–

state of health remaining capacity due to ageing

http://epg.eng.ox.ac.uk/content/degradation-lithium-ion-batteries

http://epg.eng.ox.ac.uk/content/degradation-lithium-ion-batteries


Battery failure

•

Safety=thermal stability

→Failure mechanisms–

External/internal –

internal short circuits–

Mechanical, electrical, thermal –

abusive conditions


Thermal runaway•

Failure propagation from cell to module and pack

•

Rapid temperature increase–

Most likely due to internal spontaneous short circuits due to impurities (that can grow during time as side effect of chemical reactions)

•

Avoid thermal runaway–

Overcharge/discharge protection activated by over pressure

–

Current interrupt device (CID)–

Positive temperature coefficient (PTC)

–

Separator specified for PTC & CID, layered separators for reducing internal short circuits

6.1.2.1


Energy and power demands•

Optimal performance and lifetime capacity

–

Power demand

vs energy

capacity–

Historic

use

and outlook

–

Energy capacity

and thermal

capability

6.1 vs

5.2


Charge and discharge control

•

maintain

the voltage

limits while

respecting

the current and temperature

limits

•

LOW Constant

current

charging

followed

by voltage and temperature

control

•

HIGH current

for constant

voltage

charging•

Combined

CV+CC

6.1.1


Cell balancing•

Voltage

equalization,

which

is to fill

up energy and maximize

capacity

and life by ”removing” unbalanced

weak

links

•

Active/passive

– taking/wasting

energy

W

6.2.1.4

https://en.wikipedia.org/wiki/Battery_balancing


What is a BMS really doing?•

www.youtube.com/watch?v=OG-UUXEOZ8E

http://www.youtube.com/watch?v=OG-UUXEOZ8E


BMS•

Cell protection, charge control, demand

management, SoC

and SoH

determination, cell

balancing, authentication and identification,

communication

–

are some

objectives

for BMS

http://www.mdpi.com/1996-1073/4/11/1840/htm

http://www.mdpi.com/1996-1073/4/11/1840/htm


BMS development

•

Overall functional

safety

is better

match to global FPGA than

to local

micro

processor units

–

parallelism for performance with fail-safe logic

https://www.altera.com/solutions/industry/automotive/applications/electric-vehicles/battery-management-system.html

https://www.altera.com/solutions/industry/automotive/applications/electric-vehicles/battery-management-system.html


BMS control sequence

•

Intelligent batteries

due to base functions of a battery management system

http://mocha-java.uccs.edu/ideate/courses.html

http://mocha-java.uccs.edu/ideate/courses.html


BMS Failure recognitionhttp://www.mpoweruk.com/bms.htm

http://www.mpoweruk.com/bms.htm


BMS implementation


BMS architectures for xEVs

•

Communication, reliability

and accuracy•

Practical

attachment, number

of components

and

connections•

Few

architectures

with different features in

connections

and communication

http://www.electronicproducts.com/Power_Products/Batteries_and_Fuel_Cells/Battery_management_architectures_for_H

http://www.electronicproducts.com/Power_Products/Batteries_and_Fuel_Cells/Battery_management_architectures_for_HEVs.aspx


Multicell Battery Stack Monitor

•

Component

name

LTC6802-1, Up to 12 cells, 13 ms measurement

interval, up to 1000V, passive cell

balancing

http://www.linear.com/product/LTC6802-1

http://www.linear.com/product/LTC6802-1


BMS sensor module

MM9Z1 638 4-Cell Lithium Battery BMS unit•battery stack monitor IC can measure a number of cell voltages and provide for the discharge of individual cells to bring them into balance with the rest of the stack

http://www.nxp.com/products/automotive-products/energy-power-management/can-transceivers/reference-design-mm

http://www.nxp.com/products/automotive-products/energy-power-management/can-transceivers/reference-design-mm9z1-638-4-cell-lithium-battery:RD9Z1-638-4Li


Some future trends by Bosch


Useful links•

www.mpoweruk.com

•

www.Batteryuniversity.com•

www.liionbms.com/php/cells.php

http://www.mpoweruk.com/

http://www.batteryuniversity.com/

http://www.liionbms.com/php/cells.php

10.batteries & management · 2020-04-11 · lund university / lth / iea / avo reinap / mvkf25 /...

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