SENSOR*: Embedded Fiber-Optic (FO)

Sensing for Battery Packs

*SENSOR: Smart Embedded Network of Sensors with an Optical Readout

www.parc.com/sensor

Dr. Ajay Raghavan

raghavan@parc.com | 1-650-812-4724

ARPA-E AMPED Program

2

AMPED: Advanced Management and Protection of Energy Storage Devices

SENSOR Overview

3

Online at www.parc.com/sensor

4

FO Sensor Example: Fiber Bragg Gratings

(FBGs)

wavelength

reflection

white

light

wavelength

reflection

wavelength

reflection

white

light

gain medium

fluidic

channel

mirror

n2

n1

wavelength

outp

ut

inte

nsity

wavelength

outp

ut

inte

nsity

white

light

λ1

wavelength

reflection λ1 λ1+Δλ

stimulus

white

light

λ1

wavelength

reflection λ1 λ1+Δλ

wavelength

reflection λ1 λ1+Δλ

stimulus

λ1white

light

wavelength

reflection λ1 λ1+Δλ

stimulus

λ1white

light

wavelength

reflection λ1 λ1+Δλ

wavelength

reflection λ1 λ1+Δλ

stimulus

Photonic crystal sensor

Silicon micro-sphere sensor

Surface plasmon resonance sensor

Laser cavity sensor

Fiber Bragg grating sensor

wavelength

transm

issio

n

white

lightwavelength

transm

issio

n

wavelength

transm

issio

n

white

light

5

Strain, temperature, gas,

chemical, current, voltage, ...

Multiplexable: multiple

sensors on single FO

Initial Study for External Strain, Temperature

λ2 (loose)

Readout

λ1 (fixed)

6

Picks up only

thermal strain

Picks up

total strain

Setup mimics

module pressure,

cooling

Mechanical Strain Across C Rates

7

FB

G s

ignal (p

m)

FB

G s

ignal (p

m)

FB

G s

ignal (p

m)

Curves similar across C rates, including dynamic cycles

Intercalation Stages from FBG Strain SignalF

BG

sig

na

l derivative (

pm

/s)

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SOC (%)

From Sethuraman et al. 2010

Graphite Stage 4 Stage 3 Stage 2 Stage 1

FBG derivative peaks intercalation stage transitions

Stage transitions shift

w/ life: aging metric

From Liu, P. et al. 2010

Peaks aligned

across C-rates

Cold Test at –15.5oC

Strong, accurate FBG signal even at cold temperatures9

C/10 to cell V limit

C/2 to cell V limit

~50% SoC at end of charge

accurately sensed by FBG

Electrical v/s FBG: Cell External Sensing

10

FB

G s

ignal (p

m)

FO

sig

na

l (p

m)

Str

ain

ga

ug

e s

ign

al (μ

ε)Time (hours)

FO

sig

na

l (p

m)

NT

C s

ign

al (o

C)

Time (hours)

No load CC Charge CV No load

“Loose” FBG v/s NTC thermistorFBG strain v/s electrical strain gauge

Electrical strain gauge signals seem not as repeatable

NTC signal shows tendency to pick up EMI

Pouch Cells with Internally Embedded FO

Stable embedded config w/ FBGs bonded to electrode

Approach extended to large-format cells 11

15 Ah large-format

1.5 Ah small-format

Internal Small-Format Cell FBG SignalsInternal FBG signalFBG T signal

Internal signals 2-5x stronger than external

Cell internal temperature, other SOX features detectable

FB

G s

ign

al (p

m)

Time (h)

12

Internal FBG Robustness: Dynamic Cycles

13

Internal more robust than external; both better than cell V

4-Cell Module Assembly w/ Large FO-Cells

No major module assembly line changes for FO-cells

14

Optical

fibers

Connectors for cooling fins

Individual

15 Ah cell

HPPC Response at 50% SOC, 20oC

15

7C for 10s

“The ideal HPPC response”

- Major OEM battery engineers

60s rest 5C for 10s

Strain changes linearly over pulse, settles

60s rest

FBG Strain Signals: Rapid Dynamic CyclesUS06

Ce

ll #

1C

ell

#3

UDDS

Red: US06 cycles

Blue: Static cycles

Red: UDDS cycles

Blue: Static cycles

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Error of <2.5% over 5-100% SOC achieved: >2x SOTA

Initial Aggressive Cycle SOH Results

10-cycle horizon capacity prediction error of <2.2%

Number of cycles0 50 100 150

Com

pe

nsate

d s

tra

in (

pm

)

100

120

140

160

180

200

220ObservedModel

Prediction horizon Mean error Max error

1 cycle ahead 0.14% 0.38%

5 cycles ahead 0.24% 1.1%

10 cycles ahead 0.4% 2.2%

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Charge capacity (Ah)14.8 14.9 15 15.1 15.2

Com

pen

sa

ted s

train

0.1

0.12

0.14

0.16

0.18

0.2

0.22

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FO-Embedded Cells: xEV-Grade Life, Seal

Electrolyte-robust FO coatings

-60

-40

-20

0

20

40

60

0 10 20 30 40 50

Wavelen

gthshi(pm)

Time(weeks)

FBGsignal +3degC -3degC

12

12.5

13

13.5

14

14.5

15

15.5

16

0 50 100 150

DischargeCap

acity(Ah)

Cycle#

BaseCell

Fiber-op ccell

25⁰CDisharge:30ACharge:15A1C 25⁰C

Disharge:30ACharge:30A2C

Projected FO-cell life: 1100+ cycles

FO-pouch seal

integrity as good as

pouches w/o FO in

60oC, 95% RH test

Only electrolyte

(Without Cell)

FO

And One More Thing… PARC’s FO Readout

SENSOR can replace BMS electrical sensing

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From Thylen and Wosinski 2011Prototype size:

8” x 4.5” x 4”

Anticipated

production size:

3.5” x 3” x 0.7”

~$300 for high-vol. system

Drop to $150 feasible

50 fm (0.05 με) res.: 20x SOTA

Up to 480 channels at 40 Hz

External FO 2011 Volt

1 of || strings monitored

Savings: $856+ 8.3 lbs.

Cost: $294+ 0.2 lbs.

Net: $562 + 8.1 lbs.

Internal FO 2011 Volt

All cells w/ embedded FO

Savings: $1134+ 19.2 lbs.

Cost: $333 + 0.2 lbs.

Net: $801 + 18.9 lbs.

Costs comparable; internal more SOX accuracy, value

Low added $ for more sensors; more value w/ larger packs

Fewercells$100

Vharness$90

isensor$28

HighVsensor$10

Tsensor$19

Isola on$204

BMSboards$354

Electronicsrecycling

$7

Lightweight$29

Coolantsensor$15

Ext. v/s Int. FO Value: Chevy Volt Example

Fewercells$328

Vharness$90

isensor$28

HighVsensor$10

Tsensor$19

Isola on$204

BMSboards$354

Electronicsrecycling

$7

Lightweight$67

Coolantsensor$28

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SummaryExciting results for BMS sensing, cell state challenges:

In OEM discussions for further validation, tech transfer

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Fewercells$328

Vharness$90

isensor$28

HighVsensor$10

Tsensor$19

Isola on$204

BMSboards$354

Electronicsrecycling

$7

Lightweight$67

Coolantsensor$28

wavelength

reflectio

n

white

light

wavelength

reflectio

n

wavelength

reflectio

n

white

light

gain medium

fluidic

channel

mirror

n2

n1

wavelength

outp

ut

inte

nsity

wavelength

outp

ut

inte

nsity

white

light

λ1

wavelength

reflectio

n λ1 λ1+Δλ

stimulus

white

light

λ1

wavelength

reflectio

n λ1 λ1+Δλ

wavelength

reflectio

n λ1 λ1+Δλ

stimulus

λ1white

light

wavelength

reflectio

n λ1 λ1+Δλ

stimulus

λ1white

light

wavelength

reflectio

n λ1 λ1+Δλ

wavelength

reflectio

n λ1 λ1+Δλ

stimulus

Photonic crystal sensor

Silicon micro-sphere sensor

Surface plasmon resonance sensor

Laser cavity sensor

Fiber Bragg grating sensor

wavelength

tra

nsm

issio

n

white

lightwavelength

tra

nsm

issio

n

wavelength

tra

nsm

issio

n

white

light

raghavan@parc.com; Booth #1954

FO: a new BMS enabler

<2.5% accurate SOX: >2x SOTA

Practical for xEV field deployment

$-cost competitive

Red: US06 cycles

Blue: Static cycles

SENSOR Cost Est.: ’11 Volt “Ext.” v. “Internal”

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External Config 1 of

||Cost Estimate:

$303 (1M xEVs/year)

$366 (200k xEVs/year)

Internal Strain + Temp. all

cells Configuration Cost

Estimate:

$352 (1M xEVs/year)

$572 (200k xEVs/year)Cost estimates incl. assembly, on solid footing w/ new dataReadout key cost: low cost Δ to embed/sense more cells

Lightsource$10

FOsensors$34

Readout$250

Moduleconnect

$8

Recyclingfee$3

FOcellembedding

$6Controls$14

Power$1

Tech.premium

$26

Lightsource$10

FOsensors$13

Readout$250

Moduleconnect

$8

Recyclingfee$3

Controls$5

Power$1

May contain trade secrets or commercial or financial information that is privileged or confidential and exempt from public disclosure.

May contain trade secrets or commercial or financial information that is privileged or confidential and exempt from public disclosure.

New BMS Scenarios w/ SENSOR: Summary

1. xEV dynamic cycle utilization not limited by cell V

2. BMS control to maximize life w/ better cell state info:

► Detect, manage early incipient issues, excessive strain

► Track intercalation stage shifts for cell aging estimate

► Minimize temp. differential between internal/external

3. More informed charging, regen, balancing

4. Better cell utilization for cold temp. use: avoid

polarization issues in cell V

5. Enhanced safety from awareness of incipient failure

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Broad range of new use cases anticipated to enable

better BMS for longer life and pack utilization to true limitsMay contain trade secrets or commercial or financial information that is privileged or confidential and exempt from public disclosure.

May contain trade secrets or commercial or financial information that is privileged or confidential and exempt from public disclosure.

Applicable to Other Chemistries: LiFePO4

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Considerable external FBG strain signal, features

also seen in flat-voltage chemistry like LFP

Time (h)

FB

G s

ign

al (p

m)

Vo

lta

ge

(V

)

Cu

rre

nt (A

)

Ext. FBG Strain for Over-V (AA PP Pouch Cell)

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Sample point

Volta

ge (V

)C

urr

ent (m

A)

FB

G s

ignal (n

m)

V limit (4.2 V)

Clear FO strain signal change right after 1st mild overcharge

After 1st over-

V

Residual Strain Effect on Cell Performance

Residual cell strain after cycles affects performance

Cell performance and strain curves (from Wang et al., JECS ’04, ’07)

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Cell Internal Temperature: Higher C Rates

Worse (20oC) at higher C rates and large-format cells

(a) Internal 4.4 Ah LiFePO4 cell temp: 5oC, 16 C pulses, cooled;

(a)

(b)

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(b) Persistent SOC difference (from Fleckenstein et al. JPS ‘11)

Use Case #2: Control to Maximize Cell Life

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(b) 4.4 Ah LiFePO4 cell temp.: 5oC, 16 C,

cooled (Fleckenstein et al. JPS ‘11)

(c) Better SOH, capacity fade

prediction to manage cell life

(a) FBG sensors useful for detecting

excess cell strain (can lead to

electrode cracking)

SENSOR-enabled better real-time cell state awareness for

BMS to manage for longer pack life

Discharge cell capacity (Ah)0.97 0.98 0.99 1 1.01 1.02 1.03 1.04

Str

ain

at e

nd o

f cha

rge

(pm

)20

30

40

50

60

70

80

90

100

110

Discharge cell capacity (Ah)0.97 0.98 0.99 1 1.01 1.02 1.03 1.04

Vol

tage

(V

)

4.336

4.338

4.34

4.342

4.344

4.346

4.348

4.35

Discharge cell capacity (Ah)Discharge cell capacity (Ah)

Vo

lta

ge

(V

)

FB

G s

tra

in a

t e

nd

of ch

arg

e (

pm

)

Use Case #5: Enhanced Safety

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SENSOR can detect subtle failures not seen in cell V/i signals

• LCO cells fatigued under

rapid dynamic cycles

• Cell failure seen much

later in cell V (plating)

Electrical signals FBG signals and SOC

Drop in SENSOR

signal despite

expected flat SOC

from i-counting