optimizing battery run and charge times of today’s mobile ... · –gaining insights for...

Optimizing Battery Run and Charge Times of Today’s Mobile Wireless Devices

Innovative Test Techniques Yield Greater Insights

June 14th, 2016

© 2016 Keysight Technologies

Denis Glasse – Keysight Technologies

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Agenda

– Gaining insights for optimizing battery run-time

• Battery drain measurement and analysis techniques

• Battery run-down testing and analysis

– Gaining insights for optimizing battery management and charge-time

• Understanding and evaluating lithium ion battery charging and

battery charge management

• Understanding and evaluating a device’s adaptive fast charging

and its battery charge management

– Summary

2

© 2016 Keysight

Technologies

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Why is Optimizing Battery Run-time So Important Now?

– Higher data demands

– Larger displays and touch screens

– “Always-connected” applications

– Greater % of time being used

– Complex interaction of

applications/software/hardware

– Larger batteries in use still not enough!

© 2016 Keysight

Technologies 3

Top Concern to Users of Increasingly Capable Devices

Inadequate design and

analysis leads to:

– Shorter device run time

– Unanticipated periods of

high battery drain

– Additional design cycles

– Dissatisfied end-users

Optimizing battery run-time, in all

phases of design, leads to:

– Longer running, more

competitive products

– Faster time-to-market

– Less problems in field

– Delighted end-users

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Battery Drain Test and Analysis for Simulated “Real-world” Use

Challenges:

– Properly powering DUT

– Making accurate, high

resolution measurements

– Generating combinations of

DUT activities and simulating

wireless network

– Processing and managing

massive amounts of data

– Effective tools for visualizing

and analyzing results

– Development effort, resources

and time

© 2016 Keysight

Technologies 4

Traditional Solution:

Custom RF Stimulus & Current Drain Logging Setup

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Challenge: Measuring Battery Drain for Power-Savings Operation

Wireless devices operate in short bursts of activity to conserve power:

– Long periods of sleep between bursts of activity

– Resulting current drain is pulsed; extremely high peak, low duty cycle, and low

average values spanning up to 4 decades– challenging to measure accurately!

© 2016 Keysight

Technologies 5

14 s/Div 3 mA/Div

Wireless Temperature-Humidity Sensor

50 mA/Div 500 ms/Div

GPRS Mobile Phone Battery Drain for Standby

Challenge: Traditional solutions do not have the dynamic measurement range

needed to accurately measure current drain of mobile wireless devices.

14585A 14585A

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Challenges with Traditional Measurement Solutions Most common solution: Shunt + DAQ

Typical Performance:

– ~12 to16 bits resolution

– ~ 50K to 1M samples/sec

– ~ 0.2 to 1.0% gain error (shunt and DAQ)

– ~ 0.05 to 0.2% offset error (mainly DAQ)

Commonly Encountered Challenges:

– Large effort to configure and program

– Excessive peak voltage drop on shunt

– Multiple shunts needed for wider range

– Offset errors and noise limits dynamic range

of accurate measurement for signals

spanning about 2 decades

© 2016 Keysight

Technologies 6

DC source

or battery

Shunt

+ +

- - DUT current

DUT

Diff Amp MUX Gain Amp ADC

Data Acquisition Equipment Data

out +

-

PC to log

long-term

data

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Innovations for Battery Drain Characterization

– Specialized for battery drain testing:

• N6781A: 20V, +/3A, +/-20W

• N6785A: 20V, +/-8A, +/-80W

• Innovation: Seamless ranging

spans over 7 decades of

measurement from nA to A

• Up to 200 KSa/sec digitizing rate

• Battery emulation DC source

• Zero-burden current measurement

operation for testing with the battery

• For use in the N6705 mainframe

– Integrates multiple instrument functions

into a single box:

• 1 to 4 advanced power supplies;

- >28 different models available

• Digital voltmeter and ammeter

• Arbitrary waveform generator

• Oscilloscope

• Long term data logger

• Full functionality from front panel

• Gain insights in minutes, not days!

© 2016 Keysight

Technologies 7

N6781A & N6785A 2-Quadrant SMUs N6705B DC Power Analyzer Mainframe

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N678xA Seamless Measurement Ranging

8

Range Measurement

Accuracy

8 A

3 A

±(0.04% + 1.5 mA)

±(0.03% + 250 µA)

TRANSMIT / ACTIVE

STATE

100 mA ±(0.025% + 10 µA) IDLE/STANDBY STATE

1 mA ±(0.025% + 100 nA) SLEEP STATE

10 µA

±(0.025% + 8 nA)

FIXED RANGE .

Seam

less R

ange C

hanges

Am

pe

res

= Seamless range change; no interruption or lost data

8

N6785A, N6786A ONLY

N6781A, N6782A ONLY

N6781A, N6782A ONLY

© 2016 Keysight

Technologies

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Power-savings Current Drain Measurement

© 2016 Keysight

Technologies 9

Wireless Sensor Example: Test Setup

Laptop or PC

running Agilent

14585A software

N6705B DC Power Analyzer with

N6781A Source measure module

as a battery emulator

DC

in

Wireless weather station:

Base unit and wireless

temperature sensor

DC power

cable

LAN cable

11:15

78

95

PM

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The need to measure

minimum, maximum, and

everything in between:

– Pulse peak current: 21.8 mA

– Average current: 54 µA

• Pk/Avg: 404

– Sleep current: 8.7 µA

• Pk/Sleep: 2,506

• 16% of total

– Pulse period: 4 sec

– Pulse duration: 13.6 msec

• Duty cycle: 0.34%

– Transmit pulse contribution:

30.8 µA (57%)

– Processing activities

contribution: 14.5 µA (27%)

© 2016 Keysight

Technologies 10

Wireless Sensor Example: Test Results

Wireless Temperature Sensor Current Drain

0.5 sec/div 5 mA/div

14585A

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© 2016 Keysight

Technologies 11

Wireless Sensor Example: Test Result - Improvements

100 mA Fixed Range Measurement Seamless Ranging Measurement

Sleep current base, 20 µA/div

Current pulses (off scale)

Sleep current base, 20 µA/div

Current pulses (off scale)

0.5 sec/div 0.5 sec/div

Range 3 A 100 mA 1 mA 10 µA Measurement

Accuracy ±(0.03% + 250 µA) ±(0.025% + 10µA) ±(0.025% + 100 nA) ±(0.025% + 8 nA)

Seamless measurement between these 3 ranges

Parameter Fixed Range Seamless Improvement

Overall DC accuracy (54 µA avg) 18.9% 0.245% 77 X

Sleep current DC accuracy (8.7 µA avg) 115% 1.18% 97.5 X

Sleep current AC noise floor ~47 µA p-p ~10 µA p-p 4.7 X

14585A 14585A

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Greater Time Resolution Yields Detailed Insights

Able to correlate specific activities to current drain duration and level:

– A large portion of energy is used during the short burst of activities

– 100 µsec or better resolution provides detailed insights on RX bursts

– Validate efficiency of individual activities both in current draw and duration

– Current drain waveform is often the easiest (or sometimes only) way to observe activity duration

© 2016 Keysight

Technologies 12

Mobile Phone Discontinuous Receive (DRX) Example

GPRS Smart Phone Battery Drain for DRX Standby

• 1.22 mA sleep current during 1.25 s paging interval

50 mA/Div

500 ms/Div Sleep current base

Receive current pulses

DRX Burst Current pulse details

• 23 ms pulse: 239 mA peak & 92 mA ave.

5 ms/Div 50 mA/Div

Wake up / idle pedestal

Receive activity / RSSI

Baseband activities

Sleep base

14585A 14585A

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Agenda









– Summary

13

© 2016 Keysight

Technologies

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Detailed Battery Run-down Testing

© 2016 Keysight

Technologies 14

Mobile Phone Example: Test Setup

DUT

with

battery

Current

measure

RF

Control interface

N6705B and N6781A or

N6785A in ammeter mode 8960 Wireless

Communications Test Set DUT

PC exercising wireless

activities and running

14585A SW for battery

drain analysis

Optional PC or internet

connection for running

server applications

LAN

Voltage

measure

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Detailed Run-down (and Charge) Testing with Battery

– N6781A or /5A regulates zero volts while measuring current, i.e. zero burden shunt

• Eliminates voltage drop and impedance problems that a shunt causes

– Built-in auxiliary DVM input simultaneously measures battery voltage

– High speed simultaneous voltage and current logging yields key insights on battery

capacity and discharge and charge management

© 2016 Keysight

Technologies 15

Mobile Phone Example: Test Setup

+ _

0 Volts

A

DUT

battery

DUT

Aux in voltage measurement

Zero burden ammeter

Battery current

_

+ +

_

N6781A or /5A source/measure unit

+ _

Vout + Vout -

DC out

AC adapter

(when

charging)

Charge Discharge

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Detailed Battery Run-down Testing

Logged min, avg & max

volts, amps, & watts

Markers at start and

shutdown determine:

– I avg = 233 mA

– V avg voltage = 3.82 V

– Charge = 843 mAh

– Energy = 3.19 Wh

– Run time = 3 hr 38 min

– V shutdown = 3.44 V

Insights:

– Charge used (843 mAh) was

less than spec’d (900 mAh)

– Energy used (3.19 Wh) was

less than spec’d (3.42 Wh)

– 3.44V shutdown level high

(target 3V)

© 2016 Keysight

Technologies 16

Mobile Phone Example: Test Results

N6781A SMU and 14585A Software Measuring

Battery Run-down on a Mobile Phone

Voltage

Current

Power

14585A

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Agenda









– Summary

17

© 2016 Keysight

Technologies

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Some Common Battery Terms and Ratings

Battery capacity or charge:

– Ampere-hours (Ah) = battery current (A) X time (h)

– Coulombs (C), 1C = 1amp-sec, 1 Ah = 3,600 C

Battery energy rating:

– Watt-hours (Wh) = battery rated voltage (V) X capacity (Ah)

– Joules (J), 1J = 1watt-second, 1 Wh = 3,600 J

C-rate or charge-discharge rate:

– C-rate (h-1) = charge-discharge current (A) / Battery capacity (Ah)

– Charge-discharge current (A) = C rate (h-1) * Battery capacity (Ah)

– C-rate (h-1) = 1/charge-discharge time (h)

– Example: C-rate and current to discharge a 2Ah battery in 4 hours:

• C-rate = 1/(4-hours) = 0.25 h-1

• Current = 0.25 h-1 * 2 Ah = 0.5 A

© 2016 Keysight

Technologies 18

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Validating Performance for Standard Charging Regiment

Cell must be first fully charged in order to assess its capacity:

– Constant Current followed by Constant Voltage (or CCCV) is standard charge regiment

– Cell manufacturers typically specify 1C maximum for CC phase

– 4.2V is the generally recommended float voltage for full charging for CV phase

– Charge cutoff condition is current dropping below a specified C-rate of 0.01~0.03C (1~3%)

– Typical charging time is 3 to 10 hours, depending on charging C-rate

– Note!: Adequate safety precautions must be taken when charging any cells

© 2016 Keysight

Technologies 19

Lithium Ion Battery Example: Test Setup

PC running 14585A

software

N6705B DC Power Analyzer and

N6781A operating in source mode

Cell under test

Voltage limited

constant current

charge (CCCV)

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Validating Performance for Standard Charging Regiment

Charge conditions:

– Battery discharged to 3V

– 0.3C rate for CC phase

– 4.2V float for CV phase

– Terminated at 0.01C (1%)

Test results:

– 898 mAh sourced, 99.8%

of rating

– 3.56 Wh sourced, 104%

of rating

– Total charge time 3.97 hr.

– CC phase: 2.72 hr. 68%

of time, 91% of charge

– CV phase: 1.25 hr. 32%

of time, 9% of charge

© 2016 Keysight

Technologies 20

Lithium Ion Battery Example: Test Results 14585A

Agilent N6781A applying CCCV charge

regiment to 900 mAh LiIon cell

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Agenda









– Summary

21

© 2016 Keysight

Technologies

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Tradeoffs on Lithium Ion Charging vs. Regiment

CV float phase maximizes charge:

– 4.2V max recommended for 100% charge

– BMS CV accuracy is critical!

– CV float phase adds disproportionally more time

– 100’s of cycles for <20% capacity loss

Reducing CV float level extends life:

– Up to 1,000’s of cycles for 3.9V float voltage

– Charge is ~65% with 3.9V float voltage

– Consideration when battery is built in

CC-only phase provides shortest charge-time:

– Eliminating CV float phase reduces the most time

for the amount of extra charge gained

– Most cells rated for 1C max charge rate

– Limit temperature range per JEITA

© 2016 Keysight

Technologies 22

Maximum Charge, Maximum Life, or Shortest Time

% C

ap

acity

Voltage

CC+CV float charge

CC phase charge

0.5C CC+CV float charge

1C CC+CV float charge

1C CC phase charge

0.5C CC phase charge

Ch

arg

e tim

e (m

in)

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Why is Optimizing Charge-Time so Important Now? Problem: Charge-time getting a lot longer

– Battery size has grown in today’s devices:

• 4 Ah in phones, over 9 Ah in tablets

- 1C charge rate; from 4 to over 9A!

– USB charging is limited to typically 5V, 1.5A

max (less in practice)

• Charge rates << 1C for large batteries!

– Have to charge overnight, a top dissatisfier!

Solution: USB adaptive fast charging

– USB Power Delivery 2.0 provides up to 100W

• Selectable voltage levels from 5V to 20V

• USB Type-C spec for greater currents

- 3A for micro USB connectors

- 5A for standard USB connectors

– Mobile device negotiates for higher voltage

– Provides substantial recharge in < 1 hour!

© 2016 Keysight

Technologies 23

USB standard charging

USB adaptive fast charging

Thorough design validation is critical for safe and reliable fast charging!

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Validating a Mobile Device’s Fast Charge Management

Test Objectives:

– Validate fast charge negotiation

– Determine maximum charge rates,

dissipation and efficiency

– Determine charge level at 30 and 60

min, and total time to 100% charge

– Confirm proper charge termination

Test Setup:

– DUT uses commercially available

proprietary fast charging

– N6781A measures charger

• Up to +/-3A and 25V

– N6785A measures battery


– 14585A SW logs voltage, current,

and power over time

© 2016 Keysight

Technologies 24

Smart Phone Example: Charge Cycle Test Objectives and Setup

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– Adaptive fast charge adapter

starts out at default 5V

– Verified negotiation process

details over 7.6 sec period

– Verified adapter output

increased to the requested 9V

– Determined battery charging

peaked at >3A (1.6A from

adapter)

• 0.9C rate for 3.3Ahr battery

• 14.54W in, 11.59W out

- 80% power efficiency

- 2.95W of losses

© 2016 Keysight

Technologies 25

Smart Phone Example: Charge Cycle Startup Test Results

Logging at a sufficient rate provides detailed insights into activities

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– 184 min to 100% charge

• 3.2 Ahr total charge

• 13.45 Whr total energy

– CC phase: 54 min (38%) and

2.35 Ahr (73%)

– CV phase: 130min (62%) and

0.85 Ahr (27%)

– Charging termination:

• 4.386V float (4.4V rating)

• 94.5mA cutoff (2.9% of the

1C maximum charge rate)

– Fast charge results:

• 30 min: 1.38Ahr (43%)

• 60 min: 2.58Ahr (81%)

© 2016 Keysight

Technologies 26

Smart Phone Example: Full Charge Cycle Test Results

Device demonstrated well over 2 times faster charging

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Test Objective:

– Validate fast charge performance

for high ESR (battery or setup)

Test Setup:

– DUT incorporates commercially

available proprietary fast charging

– N6781A measures charger


– N6785A directly emulates battery

• Programmable voltage:

- Battery no-load condition

• Programmable resistance:

- 115 mΩ (new battery)

- 215 mΩ (high ESR)

– 14585A SW logs voltage, current,

and power over time

© 2016 Keysight

Technologies 27

Smart Phone Example: High ESR Test Objective and Setup


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– Fast charging commenced after

negotiation, as before

– Fast charging current settled

out to 3.01A when resistance

set to 115 mΩ

• Same as a new battery

– Fast charging current settled

out to 2.42A when resistance

set to 215 mΩ

• 80% of 115 mΩ condition

• Simulates high ESR battery

- Increased charge time

• Simulates effect of using a

current shunt

- Influences actual results

© 2016 Keysight

Technologies 28

Smart Phone Example: High ESR Condition Test Results

Zero-burden current measurement between battery and BMS is necessary!

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In Summary:

– Devices operate in short bursts of activity

– Pulsed currents span 4+ decades, requires wide dynamic measurement

– Wide dynamic range of time provides greater insights on activities

– A battery’s characteristics and it’s management influence run-time

– Power source needs to be the actual battery or good emulation

– Battery run-down test yields useful insights on actual capacity delivered

– Current shunt resistance alters battery run-down and charging performance!

– Lithium ion battery charging is a two-phase regiment

– Bulk of charge is delivered in CC phase, bulk of time is spent in CV phase

– Today’s larger batteries are taking a lot longer to charge

– Standard USB charging power and current is a limiting factor

– New adaptive fast charging delivers bulk of charge in less time!

– Requires thorough design validation

© 2016 Keysight

Technologies 29

More than ever optimizing battery run and charge times are top priorities

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Useful References

© 2016 Keysight

Technologies 30

Application Booklet Brochure

Hardcopy: order part # 5991-0160EN •http://literature.cdn.keysight.com/litweb/pdf/5991-

0160EN.pdf

Hardcopy: order part # 5991-0519EN •http://literature.cdn.keysight.com/litweb/pdf/5991-

0519EN.pdf

Keysight “Watt’s Up?” Blog: •http://powersupply.blogs.keysight.com/

http://literature.cdn.keysight.com/litweb/pdf/5991-0160EN.pdf










http://powersupply.blogs.keysight.com/

http://powersupply.blogs.keysight.com/

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