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
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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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Power-savings Current Drain Measurement
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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Power-savings Current Drain Measurement
© 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
– 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
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
Page
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
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
– 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
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
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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
• Up to +/-8A and 25V
– 14585A SW logs voltage, current,
and power over time
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Technologies 24
Smart Phone Example: Charge Cycle Test Objectives and Setup
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Validating a Mobile Device’s Fast Charge Management
– 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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Validating a Mobile Device’s Fast Charge Management
– 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
• Up to +/-3A and 25V
– 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
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Technologies 27
Smart Phone Example: High ESR Test Objective and Setup
Validating a Mobile Device’s Fast Charge Management
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Validating a Mobile Device’s Fast Charge Management
– 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
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More than ever optimizing battery run and charge times are top priorities
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Useful References
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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/
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Thank You!
© 2016 Keysight
Technologies 31
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