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Page 1: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

1 © Ricardo Inc 2015 March 2015

BMS System Benchmark and Standardization

Robert Ratz

Page 2: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

2 © Ricardo Inc 2015 March 2015

Delivering excellence through experience

Providing technology, product innovation, engineering solutions and

strategic consulting to the world’s automotive industries since 1915.

Today

1915

Ricardo is a global, world-class, multi-industry consultancy for

engineering, technology, innovation, strategy and environment.

Page 3: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

3 © Ricardo Inc 2015 March 2015

As with all analysis, approximations in models, loading and interpretation exist, and real components may vary in geometry and properties from those assumed. Hence analysis results should be used only as a tool for guiding the design process and

for reducing risk of poor performance during development and validation testing. Where analysis results are described as acceptable, it is implied only that the risk of poor performance is considered acceptable to proceed to the next stage of the

design and development process, unless otherwise stated. While the analysis may reduce the amount of testing required to prove a design, it should not be considered a replacement for validation testing unless specifically stated by Ricardo.

Battery Management System

Agenda

• Ricardo Vehicle Benchmarking and Analysis

• BMS System Overview

• Types of Cell Balancing

• BMS System Benchmark Comparison

– Architecture Comparison

– Battery size

– Cell Balancing

– Isolation methods

– Voltage sense & battery balance

– Microcontrollers

• Motivation for a standardized BMS system specification

Page 4: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

4 © Ricardo Inc 2015 March 2015

Fourteen xEVs have been benchmarked over the last four years by Ricardo

High Voltage

Battery Pack

DC DC

Converter

DC AC

Inverter

Onboard

Charger

System

High Voltage

Junction Box

High

VoltageHarn

Harnes

HVAC and

Cooling

Systems

Transmission

/ EV Drive

System

Ex

am

ple

Sc

he

ma

tic

s

Ba

ttery

Pack

Th

erm

al

Ba

ttery

Pack E

lectr

ical

Introduction to EV/Hybrid Analysis Benchmarking

xEVs Benchmarked (note driveline weights shown)

Page 5: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

5 © Ricardo Inc 2015 March 2015

Benchmark activities include in-depth analysis and studies of all major EV systems

Thermal Schematic Cell Characterization BMS Analysis

Exploded Views Battery Schematic Steel Analysis System Schematic

2D CAD Drawing Circuit Analysis Performance Testing 3D CAD Modeling

Analyses performed (sample)

Introduction to EV/Hybrid Analysis Benchmarking

Page 6: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

6 © Ricardo Inc 2015 March 2015

BMS System Overview

BCM (Battery Controller Module)

• Current Sensing

• Voltage sensing

• Temperature sensing

• CAN Communications

• Battery Charger control

• Output drivers for pumps, fans, and heaters

• Contactor control:

– Main Contactors

– pre-charge

– Charger Contactors

• State of Charge algorithms

• State of health algorithms

• Power capability algorithm

• Safety feature

– Performs leakage detection and contains

ground fault interrupt functionality

– Self test of all critical functionality on every

“key-on” event

– Diagnostics of key functions

Page 7: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

7 © Ricardo Inc 2015 March 2015

BMS Architectures – Distributed

Distributed BMS Architecture is split into

one main controller and multiple slave

boards

Battery Controller Functions:

• Battery charger control

• Output drivers for pumps, fans, and

heaters

• Typically Contactor control

• State of charge algorithms

• State of health algorithms

• Power capability algorithm

• Safety feature

Slave Board (Voltage & Balance PCB)

• Voltage /Temperature

• Cell Balancing

• Communicates to main controller

Battery module

#1

Battery module

#2

)

Battery module

#3

Battery module

#4

Bat

tery

pac

k sy

stem

Traction voltage

Cell monitoring and current

balancing circuits #1

(Red PCB)

Cell monitoring and current

balancing circuits #2

(Blue PCB)

Cell monitoring and current

balancing circuits #3

(Blue PCB)

Cell monitoring and current

balancing circuits #4

(Green PCB)

CAN

Sys

tem

CA

N b

us

lines

CAN

CAN

CAN

CAN BMS master ECU

Pros

• Highly Scalable and modular

• Less wiring

Cons

• Several PCBs

Page 8: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

8 © Ricardo Inc 2015 March 2015

• A Centralized BMS has all of the functions in a

single module/PCB.

• Centralized architectures tend to be on smaller

packs (exception is the Nissan Leaf)

Centralized BMS

Pros

• One PCB and reduced

electronic costs

Cons

• Wiring intensive

• Not scalable

Master CPU

(uPD70F3236BM)

Battery monitor #1

(DS15110)

Ga

lva

nic

is

ola

tio

n

(op

toc

ou

ple

rs)

Battery monitor #24

(DS15110)

. . . . . . . . . . . . . . . . .

22

x D

S1

51

10

in d

ais

y-c

ha

in

Battery

module

(4 cells)

Battery

module

(4 cells)

Daisy-chain

serial

communication

interface

Battery monitor #25

(DS15110)

2x96 cells in

parallel

configuration

Battery

192 cells

CAN

driver

Co

nn

ec

tor

Page 9: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

9 © Ricardo Inc 2015 March 2015

Cons

• More Complex

• More expensive

Passive Balancing

• Resistive discharging of higher voltage

cells to the lowest denominator

Pros

• Integrated ASICs

• Least expensive

Active Balancing

• Charges a low cell from a higher cell

Pros

• Quicker to balance

• Capable of nurturing

a weak cell to prolong life

• Recovers energy

Cell Balancing

VDD

CB8

IN8

IN7

Voltage measurement circuit and

cell balancing FET for each cell

3.75V

. . . . .

Cell 1

3.75V

Cell 8

6x same block

IN1

CB1

IN0VSS

Mux ADCSPI

interfaceto the

CPU

30R

30R

L9763

IN2

IN3

IN4

IN5

IN6

5V LDO

5V SMPS

+5V

+5V

CB1

CB8

Cell balancing

control circuits. . . . .

Daisy-chain

interfaceto other

L9763

IN1

CB1

IN0

VSS

Mux Serial

interface

Charge

pump with

switch

matrix

2P25 SF367

IN2

IN3

1.2V

1.2V

CB2

CB3

CB4

VDD

Current

balancing

control logic

ADC

Unknown

interface

Connect to next

2P25 SF367 in

daisy-chain

CB5

CB6

IN4

IN5

IN6

to next 6 cells

to next 6 cells

6 c

ells

in

se

rie

s

CB0

Charge balancing

capacitor

Cons

• Slower Balancing

• Wastes energy to heat

Page 10: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

10 © Ricardo Inc 2015 March 2015

BMS Benchmark and Analysis

• Analyzed BMS PCB

• Determined PCB functional partitioning

• Developed system diagrams

2011

Chevrolet

Volt

2011

Nissan

Leaf

2012

Toyota

Prius Plug In

2011

Mitsubishi

iMiEV

2013

Chevrolet Malibu

Eco

2013

Ford

Fusion

Master CPU

(R5F7142)

Battery monitor #1

(HCC03-LLV1018)

Galvanic isolation (optocouplers)

Battery monitor #2

(HCC03-LLV1018)

Battery

module

(6 cells)

Battery

module

(6 cells)

Battery

16 cells

CAN

driver

Co

nn

ec

to

r

Battery monitor #3

(HCC03-LLV1018)

Battery

module

(4 cells)

Battery monitor #6

(HCC03-LLV1018)

Battery monitor #5

(HCC03-LLV1018)

Battery

module

(6 cells)

Battery

module

(6 cells)

Battery

16 cells

Battery monitor #4

(HCC03-LLV1018)

Battery

module

(4 cells)

Daisy-chain

synchronous serial

communication

interface

Ground

fault

detection

+115V

Daisy-chain

synchronous serial

communication

interface

Daisy-chain

synchronous serial

communication

interface

Daisy-chain

synchronous serial

communication

interface

Synchronous serial

communication

interface

Synchronous serial

communication

interface

Battery monitoring

circuits block #1

Ga

lv

an

ic

is

ola

tio

n (o

pto

co

up

le

rs

+

o

pto

MO

S)

Battery

(8 triplets)

Battery pack #1

(30 cell triplets)

CAN

driver 1

Co

mm

un

ic

atio

n in

te

rfa

ce

c

on

ne

cto

r (b

la

ck

)

Battery monitoring

circuits block #2

Battery

(8 triplets)

Battery monitoring

circuits block #3

Battery

(8 triplets)

Battery monitoring

circuits block #4

Battery

(6 triplets)

CAN

CAN

driver 2

CAN

driver 3

CAN

driver 4

CAN

CAN

CAN

Status signals

Control signals

Cell monitoring

circuits #1

Cel

l mon

itori

ng c

ircu

its #

2

Cel

l mon

itori

ng c

ircu

its #

3

Cel

l mon

itori

ng c

ircu

its #

4

Isol

atio

n ba

rrie

r

CAN interface

Isolation barrier

Isolated

interface

IN1

CB

1

IN0

VS

S

Mux

Serial

interface

Integrated

4x FE

T

switches

DS

15110

IN2

IN3

3.75V

3.75V

3.75V

3.75V

430R

430R

CB

2

CB

3

CB

4

VD

D

430R

430R

Current

balancing

control logic

AD

C

UA

RT

interface

Connect to

next DS

15110

in daisy-chain

To next battery

stack in series

To next battery

stack in series

Master CPU

(uPD79F0121A)

Battery monitor #4

(2P25 SF367)

Galvanic isolation (optocouplers)

Battery

module

(6 cells)

Daisy-chain

communication

interface

Battery

module

Daisy-chain

communication

interface

Daisy-chain

communication

interface

Daisy-chain

communication

interface

Ground

fault

detection

Battery monitor #3

(2P25 SF367)

Battery monitor #2

(2P25 SF367)

Battery monitor #1

(2P25 SF367)

Daisy-chain

communication

interface

Battery

module

(6 cells)

Battery

module

(6 cells)

Battery

module

(6 cells)

Battery monitor #5

(2P25 SF367)

Battery

module

(6 cells)

Battery monitor #6

(2P25 SF367)

Battery monitor #7

(2P25 SF367)

Battery monitor #8

(2P25 SF367)

Battery

module

(6 cells)

Battery

module

(6 cells)

Battery

module

(6 cells)

Daisy-chain

communication

interface

Battery

module

Next module Previous

module

V+

S8

C8

C7

Vo

ltag

e m

ea

su

rem

en

t circ

uit a

nd

ce

ll ba

lan

cin

g F

ET

for e

ach

ce

ll

3.7

5V

. . . . .

Ce

ll 1

3.7

5V

Ce

ll 8

6x s

am

e b

lock

C1

S1

V-

Mu

x

DS

AD

C

12

.bit

Co

ntro

l

circ

uits

41

R

41

R

LT

C6

80

2-2

C2

C3

C4

SP

I

inte

rface

Re

fere

nce

vo

ltag

e

To

CP

U

AD7280

Master CPU

(MPC5534MVZ80)

Pack

of 5

cells

. . . . . .

6x

AD7280Pack

of 6

cells

. . . . . .

7x

. . . . . . . . . . .

5x battery pack

in a daisy-chain

. . . . . .

5x monitoring

circuits AD7280

SPI(1)

SPI(7)

VSS(1)

VSS(7)

AGND7

SPI

6x6 cells (36 in total) monitoring and signal

processing in this block

AD7280Pack

of 6

cells

. . . . . .

7x

AD7280Pack

of 6

cells

. . . . . .

7x

. . . . . . . . . . .

4x battery pack

in a daisy-chain

. . . . . .

4x monitoring

circuits AD7280

SPI(8)

SPI(13)

VSS(N)

VSS(0)

AGND13

Ga

lva

nic

is

ola

tio

n

Ad

UM

14

00

+ A

Du

M5

40

3

SPI

5x6 cells and 2x5 cells (40 cells in total) monitoring and signal

processing in this block

SPI

Ga

lva

nic

is

ola

tio

n

Ad

UM

14

00

+ A

Du

M5

40

3

• Analyzed subsystems

• Voltage & Temperature sensing

• Balancing methods & IC’s used

Page 11: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

11 © Ricardo Inc 2015 March 2015

Car model Year BMS architecture kWhr

Ford Fusion

Hybrid 2.0

2013 Centralized on the single PCB 1.4

Chevrolet

Malibu ECO

2013 Centralized on the single PCB 0.5

Chevrolet Volt 2011 Pseudo-Distributed 4 PCB

modules + BMS master ECU

16

Mitsubishi

I-MiEV

2012 Distributed 11 PCB modules +

BMS master ECU

16

Nissan Leaf 2011 Centralized on the single PCB 24

Toyota Prius 2012 Distributed 4 PCB modules 4.4

Ricardo

McLaren P1

2013 Distributed 1 BCM + Several

VTBMs

4.8

There Are Two Main Architectures

Centralized

Distributed

Master

controller

Slave PCBs

Page 12: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

12 © Ricardo Inc 2015 March 2015

Car model Battery voltage Battery

cells

Ricardo McLaren P1 550V 324

BMW i3 360V 96

Tesla Model S60 300V 5,376

Ford Fusion Hybrid 275V 76

Chevrolet Malibu ECO 115V 32

Chevrolet Volt 360V 288

Mitsubishi I-MiEV 330V 88

Nissan Leaf 360V 192

Toyota Prius PlugIn 207V 56

Battery Comparison

Ford Fusion Hybrid Nissan Leaf Chevy Volt Prius Plug-In Hybrid

Page 13: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

13 © Ricardo Inc 2015 March 2015

Car model Cell balancing method Cell balancing

technique

Cell balancing

current1

Ford Fusion Hybrid Passive Resistive 17 mA

Chevrolet Malibu ECO Passive Resistive 17 mA

Chevrolet Volt Passive Resistive 125 mA2

Mitsubishi I-MiEV Passive Resistive 92 mA

Nissan Leaf Passive Resistive 8.7 mA

Toyota Prius Active Charge pump Unknown

Ricardo McLaren P1 Active & Passive Charge transfer &

resistive

1Amp Active

250 mA Passive

Battery Cell Balancing Comparison

1 Estimated cell balancing current given at nominal cell voltage 2 Estimated cell balancing current given at nominal cell voltage for cell triplet

Cell Balancing

Page 14: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

14 © Ricardo Inc 2015 March 2015

Isolation Method

AD7280

Car model Isolation Method Chip

Ford Fusion

Hybrid Digital isolators

Analog Devices

ADuM5403

Chevrolet

Malibu ECO Optocouplers NEC - PS9121

Chevrolet Volt Optocouplers Avago ACPL-M43T

Matsushita AQW212S

Mitsubishi I-

MiEV

Digital isolators

Analog Device-

ADuM1402W

Nissan Leaf Optocouplers NEC - PS9114

Toyota Prius ????

Renesas &

Matsushita

PS9121

216C020

Ricardo

McLaren P1

OptoMOSFETs

Digital Isolators NEC PS710E

Page 15: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

15 © Ricardo Inc 2015 March 2015

Voltage & Balance ASICs

AD7280

Car model ASIC # cells Communications

from ASIC to Micro

Ford Fusion Hybrid Analog Devices

AD7280 6 Cells SPI Daisy Chain

Chevrolet Malibu ECO Hitachi-

HCC03LLV1018 6 Cells Serial Daisy chain

Chevrolet Volt STMicro

L9763 8 Cells SPI Daisy Chain

Mitsubishi I-MiEV Linear-

LTC6802G-2 12 Cells

SPI Daisy Chain

Nissan Leaf NEC

DS15110 4 Cells

UART interface

Toyota Prius ????

2P25 SF367

4 Cells

Serial Daisy chain

Ricardo McLaren P1 Microcontroller 14 Cells NA

IN1

CB1

IN0

VSS

Mux Serial

interface

Charge

pump with

switch

matrix

2P25 SF367

IN2

IN3

1.2V

1.2V

CB2

CB3

CB4

VDD

Current

balancing

control logic

ADC

Unknown

interface

Connect to next

2P25 SF367 in

daisy-chain

CB5

CB6

IN4

IN5

IN6

to next 6 cells

to next 6 cells

6 ce

lls in

ser

ies

CB0

Charge balancing

capacitor

Page 16: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

16 © Ricardo Inc 2015 March 2015

BMS Primary CPU

Car model BCM CPU

Ford Fusion Hybrid Freescale

MPC5534MVZ80 32 Bit

Chevrolet Malibu ECO Renesas

R5F714264FPV 32 Bit

Chevrolet Volt Freescale

S9S08DZ32 32 Bit

Mitsubishi I-MiEV NEC

F3612M2 32 Bit

Nissan Leaf Renesas

PD70F3236BM 32 Bit

Toyota Prius Renesas -

PD79F0121A 32 Bit

Ricardo McLaren P1 Freescale

MC9512XPE 32 Bit

Page 17: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

17 © Ricardo Inc 2015 March 2015

Car

model

Vo

lta

ge

Se

nse

Tem

pera

ture

Sen

se

Pa

ss

ive B

ala

nc

e

Ac

tive

Ba

lan

ce

Iso

lati

on

Leakag

e D

ete

cti

on

Co

nta

cto

r D

riv

ers

Ac

ces

so

ry D

riv

es

Ch

arg

er

inte

rfac

e

CA

N

Co

mm

un

icati

on

Vo

lta

ge

< 2

50

V

CP

U 3

2 B

it

Dis

trib

ute

d

Ce

ntr

alize

d

Ford Fusion

Hybrid X X X X X X X X X X X X

Chevrolet

Malibu ECO X X X X X X X X X X X

Chevrolet

Volt X X X X X X X X X X X X

Mitsubishi I-

MiEV X X X X X X X X X X X X

Nissan Leaf X X X X X X X X X X X X

Toyota Prius X X X X X X X X X X X

Ricardo

McLaren P1 X X X X X X X X X X X X X

Architecture Functions Summary

Page 18: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

18 © Ricardo Inc 2015 March 2015

• A global standard for BMS will further reduce high cost energy storage systems

– BMS electronic cost in the range of $500 to $1500 per battery Target $50

• BMS systems in use today have similar architectures and functions

• A BMS standard will improve safety and image of HEV/EV market

• A single specification can cover the two approaches to the architectures:

– Distributed

– Centralized

• BMS’s system hardware have 90% of common functions

– ASICs have common functions of voltage & temperature monitoring and

passive balancing

– Balancing is predominantly Passive with a couple of applications using Active

– Isolation is predominantly Opto-isolators

– Microcontroller are 32 bit

• Most of the IP is software related

• A common standard would further enable second life use of battery systems

Rational for a Standardized BMS System

Page 19: Robert Ratz BMS System Benchmark and Standardization · PDF fileBMS System Benchmark and Standardization Robert Ratz . ... modules + BMS master ECU 16 Mitsubishi controllerI-MiEV Ricardo

19 © Ricardo Inc 2015 March 2015