Post on 26-Mar-2020
Developing the battery for an electric city bus
Frieda M. DaveyProduct Engineering Daimler Buses – High-Voltage Battery
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey
Developing the battery for an electric city bus
Daimler Buses
Daimler
Trucks
Mercedes-Benz
Cars
Mercedes-Benz
Vans
Daimler
Buses
Daimler
Financial
Services
Revenue 2018
Employees 2018
Daimler Buses – A business unit of the Daimler Group
€ 26.3 Mrd.
14,070145,436
€ 93.1 Mrd.
82,953
€ 38.3 Mrd.
26,210
€ 13.6 Mrd.
18,770
€ 4.5 Mrd.
Annotation: Revenue company 2018: € 167,4 bn., Employees: 298,683
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Seite 3
Daimler Buses
City buses
Page 4
Interurban buses
Coaches
Minibuses
Product Portfolio
The Mercedes-Benz product range at a glance
Citaro* Conecto NGT + Conecto G NGTCapaCity + CapaCity L
Sprinter City
Citaro Ü*Intouro
Tourismo RHTourismoTourismo K
Sprinter TransferSprinter Travel
Citaro LE Ü*
Citaro NGT* + Citaro G NGT*
Sprinter Mobility
Conecto + Conecto G
Citaro GÜ * available as hybrid
Citaro LE*
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey
Daimler Buses
City and interurban buses
Page 5
City and interurban buses
Tour coaches
rear engine chassis
front engine chassis
rear engine chassis
Product portfolio
Mercedes-Benz chassis
* CBC = City Bus Concept (O500 also available as RF O500 M/MA/MDA)
** XBC Flexible Bus Concept
*** IBC = Intercity Bus Concept
OC 500 LE (CBC - LE)* O 500 U (CBC-LE)* OH RF (XBC)**
OF LO Boxer
O 500 RS (IBC)***OC 500 RF (IBC)***
O 500 UA
(CBC-LE-Gelenkzug)*
O 500 UDA
(CBC-LE-CapaChassis)*
O 500 RSD (IBC)*** O 500 RSDD (IBC)***
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey
Daimler Buses Page 6
Mercedes-Benz
Türk
Daimler
Buses
Mexico
EvoBus
Group
Daimler
Buses
Latin
America
Daimler Entities
Bus
Indonesia
Australia
South Africa
Daimler Buses
India
Daimler Buses - globally present
Our production sites are present all over the world
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey
Public transport needs to become more attractive at reduce
CO2 footprint and emissions at the same time.
Increasing mobility needs
Inner-city densification
Limited traffic areas
Noise pollution
Individual transport at its limits
Emission limits
Environmental zones and
access restrictions
CO2 targets (national / local)
Public funding for e-mobility
High pollution levels in cities
Public traffic needs to be part
of the solution
Need for ActionMobility Trends Legal & Political Premises
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Page 77
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey
PL 2025: 30% zero
emission
SE 2030: min.
regenerative fuel
FR 2025: 100% low emission zones
(Cities > 250.000 population)
NL 2025-30: 100%
zero emission
Source: customer interviews, press, market studies
Seite 8
DNK 2030: 100%
zero emission
1 by 1 Transformation of Diesel- to e-Buses not feasible by today
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 9
Target picture
e.g. 2025
Lower Range of Electric Buses compared to
Diesel Buses
Modification of Operation Concepts needed
Charging Systems & Interfaces to be developed
Setup of Energy Supply and Charging
Infrastructure
Standardization to be defined
Redesign of Processes required
(e.g. Service and Maintenance)
Training and Qualification
Financial Constraints
Etc.
Challenge 1: E-Buses carry only a fraction of the energy of a diesel bus.
At the same time, the weight is higher.
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 10
Diesel Bus
Tank capacity: ~ 215 l diesel
Weight: ~ 200 kg
Energy:
~ 2,100 kWh
Electric Bus
6 – 12 High-voltage batteries
Weight: ~ 1.500 – 3.000 kg
Energy:
~ 150 - 300 kWh
Challenge 2: Pure driving is possible with very little energy. Heating and
air-conditioning drastically increase the energy consumption.
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 11
En
erg
y c
on
su
mp
tio
n
Pure
Driving
Cooling
(Summer)
Heating
(Winter)
Energy consumption
nearly doubles
During winter, warm air flows out of the bus at every stop
while cold air enters.
Hence the energy needed for heating is very high.
In summer, air-conditioning leads to similar effects.
Challenge 3: The depot needs a completely different electricity supply
infrastructure to charge a fleet of electric buses.
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 12
150 kW
One charging station
for an electric bus
has a similar power
demand as 75
households.
75
Transformer
Medium voltage
10 – 30 kV
Depots for electric buses are
directly connected to the medium
voltage grid and need
transformers on the depot.
5 -10 min
2 – 5 h
Charging of an electric bus
requires several hours. For this,
all processes in the depot need
to be adapted..
Challenge 4: Various battery types with different properties and
development roadmaps are available
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 13
Battery TypeNMC(Nickel-Manganese-Cobalt)
Solid-State (Lithium-Metal-Polymer)
LFP(Lithium-Iron-Phosphate)
LTO(Lithium-Titanate-Oxide)
Charging power + + + + + + + +
Driving range + + + + 0 -
Service life + + + + + + +
Conclusion
Good trade-off between
range and charging
power. Different
operating concepts can
be realized.
Best suited for
overnight charging
concepts with long daily
runs thanks to high
capacity.
Similar to NMC but
lower range at given
weight. Higher self-
discharge causes
balancing issues.
Only suitable for
opportunity charging
concepts with very
short distances and fast
recharging.
Comparison of different offers difficult
Selection of suitable operating concept for battery type
How does the future look like Can the battery be upgraded?
Challenge 5: E-Bus workshops require new equipment and staff training.
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 14
Roof working structure
Crane system
Testing and charging equipment
Safety equipment
HV sensibilization
Specialist for HV vehicles
Working under voltage
Responsible electrician for HV systems
Energy Efficiency
Main development focus was modularity and energy efficiency
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 15
Modularity and FlexibilityProject Status
low
highBattery Capacity
Charging OptionsPanto-
graph
CCS
Plug
Transition
Period
Summer Winter
Driving Auxiliaries Heating Cooling
Thermal Management
Energy ManagementHeating
Cooling
Maximum Range
Start of Delivery
Solo: Q1/2019
Articulated: Q2/2020
Solo RHD: Q4/2021
~88 ~130
Vehicle Type
Daimler Buses
Bild vom EDB und Kerndaten
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Seite 16
Our first step in electrification
of public transport
as platform for eMobility
The new Mercedes-Benz eCitaro
A sophisticated starting point of an eMobility platform
• 8 t front axle • Modular
battery
clusters
• Rear axle
with 2 electric motors close to wheel hub
• Battery cooling system
• Cooling system for drivetrain and auxiliaries
• CO2 air conditioning with heat pump
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 17
Customer operations
with major deviations
• Operation area
• Line topography
• Infrastructure
• Operational processes
Charging systems
Depot or opportunity charging
Vehicle preparation and service
Evaluation of customer requirements
Requires more than a singular technology approach
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 18
infrastructure,
charging systems
Operation area
inner city
outer city
…
suburbs
Technology roadmap considers availability and maturity
Portfolio will significantly grow in 2020 to cover majority of demands
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 19
Vehicle
Charging system
+
+
Battery system
+
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 20
Developing the battery for an electric city bus
Secondary cell
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 21
Cathode matrix
Anode matrix
Cathode Separator Anode
Liquid electrolyte
Discharge
Daimler Buses
Cell chemistries – an overview
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Seite 22
Lithium-Sulphur Battery
Energiedichte (wg. Lithium)
Leistungsdichte
Schnellladen
Zyklenfestigkeit
Sicherheit
Kosten
Nachhaltigkeit
All Solid-State Battery
Energiedichte (v. a. Lithium)
Leistungsdichte
Schnellladen
Zyklenfestigkeit
Sicherheit
Kosten
Nachhaltigkeit
LIB with Li-Metal-Anode
Energiedichte (insb. Wh/l gering)
Leistungsdichte
Schnellladen
Zyklenfestigkeit
Sicherheit
Kosten
Nachhaltigkeit
Maturity: high - industrialized Maturity: low - developmentMaturity: very low - researchMaturity: low - development
Lithium-Ion-Battery (LIB)
EV, EES, Electronics, Drones Aviation, EES, possibly EVsPossibly EVsDrones, Electronics, (possibly EVs)
Li-Metal-Polymer-Battery
Energiedichte
Leistungsdichte
Schnellladen
Zyklenfestigkeit
Sicherheit
Kosten
Nachhaltigkeit
Maturity: intermediate
EV, EES
Cathode matrix
Anode matrix
Cathode Separator Anode
Load
Liquid electrolyte
Discharge
• Energy density
• Power density
• Fast charging
• Cyclability
• Safety
• Cost
• Sustainability
• Energy density
• Power density
• Fast charging
• Cyclability
• Safety
• Cost
• Sustainability
Cathode matrix
Lithium metal Discharge
Load
Cathode Separator Anode
Liquid electrolyte Protection layer
Cathode matrix
Lithiated cath. Discharge
Cathode Anode
Inorganic solid electrolyte = separator
Aode
• Energy density
• Power density
• Fast charging
• Cyclability
• Safety
• Cost
• Sustainability
Cathode matrix
Lithium Sulphide. Discharge
Load Load Load
Cathode Separator Anode
Liquid electrolyte
• Energy density
• Power density
• Fast charging
• Cyclability
• Safety
• Cost
• Sustainability
Cathode matrix
Lithiated cath. Discharge
Cathode Anode
Polymer solid electrolyte = separator
• Energy density
• Power density
• Fast charging
• Cyclability
• Safety
• Cost
• Sustainability
Daimler Buses
LIB - Typical cathode materials
• NMC Lithium-Nickel-Manganese-Cobalt-Oxid
• LMO Lithium-Manganese-Oxide
• LFP Lithium-Iron Phosphat
• NCA Lithium-Nickel-Cobalt-Aluminium-Oxide
• …
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Seite 23
Cathode matrix
Anode matrix
Cathode Separator Anode
Liquid electrolyte
Discharge
Daimler Buses
LIB - Typical Anode Materials
• Graphite with intercaleted Li-ions
• Addition of Silicon for improved energy density
• LTO Lithium Titanium Oxide for fast charging
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Seite 24
LIB - Typical Electrolytes
• LiPF6 in organic solvent
• Additives for anode passivation, cathode protection, overcharge protection, safety, flame protection, lifetime,
reduction of gas formation…
• Ionic Liquids for flammability reduction
LIB - Separators• Polymer and/or ceramic
Cathode matrix
Anode matrix
Cathode Separator Anode
Liquid electrolyte
Discharge
Charging power (kW)
Opportunity
charging
Battery strategy has to consider different applications
Two technology approaches to cover operation scenarios
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 25
Useable energy (kWh)
Depot
charging
• High charge power
• Medium
energy density
1st step
solid-state battery
• High energy
density
• Low
charge power
2nd step
+
Li ion
battery
(NMC)
Modular layout
• Established cell chemistry
• Applicable for opportunity and depot charging
• Cooling required
NMC Battery technology is based on modular concept
Evolution of modules for higher capacity in next step
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 26
• Anode: Graphite structure
• Cathode: NMC structure
(Nickel-Manganese-Cobalt)
• Ceramic separator & liquid electrolyte
cathode separator anode
liquid electrolyte
load
Li+cathode matrix
anode matrix discharging
New technology
• High energy density
• Inherently safe and sustainable cell chemistry
• Approximately 80kW charging power
• No cooling required
• Long lifetime perspective
Solid-state batteries are second technology path
Combination of high energy density and long lifetime perspective
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 27
• Anode: Pure Lithium metal
• Cathode: LFP
• No additional separator
• Solid-state polymer electrolyte
cathode anode
polymer electrolyte = separator
load
discharging
cathode matrix
cathode with Li
Li+ Li atom
Solid-state batteries enable maximum range with depot charging
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 28
Lithium-ion
NMC
Solid-state
battery
Useable energy [kWh] + + + +
Energy density [kg/kWh] + + + +
Lifetime [years] + + + +
Charging power + + + +
Flexible for depot and
opportunity charging
Depot charge
with maximum range
Daimler Buses
Definitions
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Page 29
• BoL Beginn of Life
• EoL End of Life
• SOH State of Health
How healthy is the HV Battery? How much has it aged?
• SOC State of charge
How much energy is in the HV Battery?
SOH =90% SOH =80%
Capacity HV Battery =100%
Capacity HV Battery = 80%
100% 40%
SOH =100%
Daimler Buses Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Page 30
• DOD Depth of Discharge
How much energy per discharge is being extracted?
• SOC Range
In what range of SOC is the HV Battery being used?
• C – Rate
How fast is the HV Battery charged/discharged?
• Cyclability ( ≈ Lifetime)
How many times can the HV Battery be discharged of a DOD = X, temperature =Y, with a C-Rate =Z?
80% DOD 40% DOD
0%
100%
20%40%
SOC Range: 20% - 40% (DOD = 20%)
0%
100%
60%80% SOC Range: 60% - 80% (DOD = 20%)
Daimler Buses
Influencing factors on cyclelife
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Page 31
The lower the C-Rate…
…the higher the lifetime
C-Rate Lifetime
T = ideal T
T ≠ ideal T
Lifetime
Lifetime
Daimler Buses Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Page 32
The smaller the DOD…
… the longer the lifetime
DOD Lifetime
The lower the SOC range…
… the higher the lifetime
SOC Range Lifetime
Relevant Parameters
Daimler Buses
Calendaric vs Cycling Aging
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Page 33
Calendaric aging
Aging fators:
• Storage temperature
• Storage SOC
Cyclic aging
Aging factors:
• Temperature
• C-Rate
• SOC Range
• DOD
Overall aging
• Depending on the power- and driving-profile, the HVB lifetime is more dependant on cyclic or calendaric
aging
• In general: Cars Driven little, parked a lot Calendaric Aging
City Bus Driven a lot, parked little Cyclic Aging
Daimler Buses Page 34
Cathode AnodeElectrolyte
Li+
e-
SE
I
SE
I
Electrolyte
Li+
e-
SE
I
SE
I
AnodeCathode
EoL:
• Side reactions at the interfaces. Part of the active material lost,
energy content decreases.
• By moving in and out of the electrode microstructure, the lithium ions
create micro cracks in the electrode material. The lithium ions have
increasing difficulty in diffusing, ionic resistance in the cell increases,
energy content decreases.
• The cracking of the electrodes leads to increase in volume in the cell
called „swelling“
BoL:
Cell aging
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey
Daimler Buses
Cell formats
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Seite 35
Pouchcell
Hardcase
CostsIntegrability
Density
Swelling
CyclabilityCooling
Manufacturing
Safety
Cylindrical
Daimler Buses Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Seite 36
BEV Cells (Energy Cell)
• Higher capacity (more active material)
Thicker electrodes to host more Li+
Fewer rolls of electrodes+separator fit within the cell
Longer path for the Li+ to travel between cathode and anode
Higher internal resistance (reduced cyclability)
Meant for constant current over time
• Often bigger
• „Simple“ chemistry
Technical battery requirements for a bus:
• high cyclability (long lifetime of the battery on the bus) PHEV cell
• high capacity (high driving range of the bus) BEV cell
BEV cells fulfill certain of our requirements, PHEV cells fulfill others Compromise needed
PHEV vs. BEV cells
PHEV Cells (Power Cell)
• Lower capacity (less active material)
Thinner electrodes
More rolls of electrodes+separator fit within the cell
Shorter path for the Li+ to travel between cathode and anode
Lower internal resistance (improved cyclability)
Higher C-rates are possible
• Often smaller
• Improved and fined tuned chemistry
Cathode
Anode
Daimler Buses Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey Seite 37
PHEV vs. BEV
Example
- 300-400 km range (very high capacity)
- Only ca. 500 cycles (very low cyclability)
CAR: Assuming ca. 50 km/day 1 cycle per week 500 weeks ca. 9 years (calendaric aging not considered,
altough relevant)
BUS: A bus does 1 cycle per day 500 cycles 500 days Life < 1,5 years (!!!!)
Even if the bus is a BEV (battery electric vehicle), PHEV cells also need to be considered
to guarantee lifetime (cyclability)
Bus requirements ≠ Car requirements
Energy consumption
[kWh/km]
For evaluation of battery technology
driving cycle and temperature scenario need to be considered
10 12 14 16 18 20 22 24
Driving
Ventilation
Summer / air conditioning
Winter / electric heating
SORT1
cycle
SORT2
cycle
SORT3
cycle
Average vehicle speed [km/h]
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 38
+200%
Customer route coverage*
Coverage of entire customer operations
Range extender as effective completion of portfolio
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 39
Operation range [km]
Segment 1 Segment 2 Segment 3
Not covered by
depot charging
Potential solid-state battery >70%
Potential NMC battery appr. 50%
* sum of 1270 vehicle operations analysed
Potential for range extender
Solo & Articulated
Charging systems
Battery technologies
Fuel cell range extender
eMobility Consulting
Comprehensive approach
for electric mobility systems
The new Mercedes-Benz eCitaro
Fully embedded in a integrated eMobility system
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 40
Mercedes-Benz eCitaro
Coverage of relevant operational
requirements with a modular kit
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 41
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 42
Thank you
Developing the battery for an electric city bus | Daimler Buses | Frieda M. Davey 43