How to Perform Battery
Discharge Testing
Daniel Carreno
Applications Engineer, TSG
Moderator
qMichael Fleischer
qDigital Marketing Specialist
Q&A
qSend us your questions and comments during the presentation
Today’s Presenter and Panelists
qPresenter
qDaniel Carreno
qApplications Engineer
qPanelists
qVolney Naranjo
qSenior Applications Engineer
How to Perform Battery
Discharge Testing
Daniel Carreno
Applications Engineer, TSG
Agenda
Basic Concepts
Standards
IEEE Recommendations
Running a Test
Results and Report Review
Tools
6
Basic Concepts
7
Introduction
• Batteries
• Energy storage device that dies naturally
• Life expectancy is seriously affected by
operating conditions
• Critical component of the electrical system
• Require periodic maintenance to achieve the
life expectancy
• Several maintenance testing methods to
determine battery conditions
• Float current
• Ohmic testing
• Load Test
8
tdworld.com: Do You Know Where Your Batteries Are?
Introduction
• Load testing is the only proven
method to determine
• Capacity of the battery
• True State of Health (SOH)
• Remaining life
• Load testing is a time and resource
demanding test
• Proper understanding of procedures
• Adequate tools
• This presentation applies mainly to
VLA, VRLA, Ni-Cd and focuses on
IEEE procedures
9
https://www.radiology.ca/article/how-does-exercise-stress-test-work
Capacity
• Quantity of electricity or energy a battery can deliver
• Usually expressed in ampere-hours
• Depends on the amount of active material
• As active material ages, the capacity reduces
• Maintenance and operation affects the capacity
100% Capacity
80%
Capacity
Lost
capacity
10
50%
Capacity
Lost
Capacity
Capacity
• Nominal Capacity
• Quantity used to identify the capacity of a battery in the nameplate
• Typically corresponds to 8- or 10-hour rates
• This is not the only rate to consider on a battery
• Rated Capacity
11
Capacity
• Rated capacity
• Quantity of electricity, declared by the manufacturer, which a battery can
deliver under specified conditions
• End voltage, reference temperature (20 or 25 C), specific duration (minutes or hours)
• End voltage equated approx. to 80% depth of discharge (DoD)
12
State of Charge
• It does not indicate the capacity
• Determined by the charging current, or float voltage, float
current and specific gravity (pending plate material)
• Battery has to be fully charged for proper capacity test
• Directly related to Open Circuit Voltage
Fully
Charged
Discharged
Partially
Discharged
13
Capacity Vs State of Charge
100%
Capacity
100%
Capacity
90%
Capacity
90%
Capacity
Fully
Charged
Fully
Charged
Partially
Discharged
Lost
capacity
Lost
capacity
Discharged
14
80%
Capacity
Fully
Charged
Lost
Capacity
Battery Maintenance
Standards
Standards
• IEEE 450 – Recommended Practice for Maintenance, Testing & Replacement of
Vented Lead Acid Batteries for Stationary Applications
• IEEE 1106 - Recommended Practice for Installation Maintenance, Testing, and
Replacement of Vented Nickel-Cadmium Batteries for Stationary Applications
• IEEE 1188 - Recommended Practice for Maintenance, Testing and Replacement of
Valve Regulated Lead-Acid Batteries for Stationary Applications
• IEEE 1184 - IEEE Guide for Batteries for Uninterruptible Power Supply (UPS) Systems
• NERC PRC-005-6 – Protection system maintenance requirements (VLA, VRLA, NiCd)
• IEC 60896-11: Vented Lead Acid - General Requirements and methods of tests
• IEC 60896-21: Valve regulated Lead Acid - Methods of test
16
Standards
https://us.megger.com/support/technical-library/academic-papers/standard-battery-testing-requirements-summary
17
IEEE Standards
• Safety
• Maintenance
• Inspections
• Corrective actions
• Type of Load Tests
• Schedule
• Procedures for Load Tests
• Battery replacement criteria
• Recycling and disposal
• Spill containment
• Annexes
18
Type of Tests:
@ Factory or
Upon
Installation
Specific
constant
discharge
rate &
duration
Baseline for
trending
Acceptance
Test
Acceptance
based on the
TimeAdjusted
Method
Measures
%C, ³ 90% of
rated
Capacity
Capacity may
rise after use
19
Type of Tests:
Measures the
%C,
To reflect
maintenance,
do not
prepare the
battery
Constant
current or
power
Performance
Test
For trending:
Prepare the
battery
https://www.radiology.ca/article/how-does-exercise-stress-test-work
20
Similar in
duration to
duty cycle
Test
periodically.
Every 25% of
Life
Type of Tests:
If fails:
review
sizing,
maintain &
equalize
Ability to
meet a
specific
application
Ability to
meet the
duty cycle
Service Test
IEEE485
21
Discharge
rate as
close as
practical to
duty cycle
At discretion
in between
performance
tests
As found, no
preparation,
no
temperature
correction
Type of Tests:
Aging factor
needed to
calculate
minimum test
duration
Constant
current
modified to
include duty
cycle
Tests ability
to meet the
duty cycle
Modified
Performance
Test (MPT)
Three types
of MPT
described in
IEEE450
(Annex I)
Measures
%C, uses
T correction
Initial
conditions
same as
Service test
22
Testing Schedule
Acceptance test
Performance/Modified Performance/Service Tests
Percentage of estimated lifetime
0%
25%
50%
75%
85%
Production
At delivery:
Discharge test
Impedance test
(baseline)
After each 25% of passed estimated lifetime:
Perform capacity test
After 85% or at
a 10% drop of
capacity:
Perform tests
annually
Applicable standards
** Many users perform an
* Procedures etc depend on many
additional test just before the
factors, e.g. typ of battery and applicable end of the warranty time of the
standard. See comments for details
battery bank
23
*** Impedance tests done e.g.
once a year can be used to
trigger a capacity test when the
result indicates an issue
IEEE 450
flooded lead-acid
IEEE 1188
sealed lead-acid
IEEE 1106
nickel-cadmium
Capacity Calculation Methods
Time Adjusted
𝑡!
𝐶=
×100
𝑡" ×𝐾#
𝑡! : actual time of test, 𝑡" : rated time
to mínimum voltaje, 𝐾# : correction
factor for temp. before start
Acceptance, Performance &
Modified Performance
Tests ³1 Hr
24
Capacity Calculation Methods
Rate Adjusted
𝑋! ×𝐾$
𝐶=
×100
𝑋%
𝑋! : actual rate used for test, 𝑋" : published
rating for time to minimum voltaje, 𝐾# :
correction factor for temp. before start
Acceptance & Performance
Tests
Tests £1 Hr
25
Before the Test
26
Initial Conditions
1. Equalize
• Follow
manufacturer
recommendations
• Return to float for
minimum of 72
hours
• Exceptions
• VRLA
• Service test
27
2. Check battery
connections
• Terminals and
strap
resistances
3. Record floating
conditions
• Float current
• Float voltage
of each cell
4. Record
electrolyte
conditions
• Temperature
of 10% or
more of the
cells
• Establish
average
temperature
Initial Conditions
5. Battery float
voltage
• Voltage at the
terminals of
the battery
28
6. Precautions to
avoid disturbances
• Isolate from
other batteries
or from critical
loads
• Connect back
up system
7. Disconnect
charger
• Follow proper
procedure for
charger
shutdown and
disconnection
8. Battery ready
for testing
• Battery
unavailable
• During and
after test
Discharge Rate
• Acceptance &
Performance Tests
• Manufacturer tables
• Service Test
• Duty cycle
• Modified Performance Test
• Duty cycle
• Manufacturer tables
• Results Trending
• Same test rate for the for the
life of the battery
29
IEEE Std. 485
Running a Test
30
Procedure
• The battery needs
preparation and maintenance
prior to the test
• Battery is unavailable during
and after the test
• The following is required for
testing
• Discharge table
• Load bank
• Backup plan
31
Running a test
• Preparation and logistics
• Current cable length
• Room temperature
• Cell by-pass
• Availability
• Bigger load bank, cables and
terminals for connections
• Heat ventilation or longer cables
• Long duration/low rate
• Load totally off-line
• Conflicts with availability of the
system
• Load supplied from the charger
with risk of outage
• Smaller load bank
• Temporary battery backup
32
• Short duration/high rate
• Higher man-hours
Test Connections
33
Test Connections
34
Test Connections
35
Temporary Battery Backup
36
Temporary Battery Backup
37
Temporary Battery Backup
38
During the Test
• Only one pause, no longer
than 6 minutes
• Measure cell voltages
preferably throughout the test
or at least 3 times during the
test:
• Start
• Middle
• End
• Avoid room temperature
increase
39
When to Stop the Test
• Discharge until voltage
decreases to the minimum
average voltage per cell
• # of cells X Min. V/cell
• 60 X 1.75 = 105V
• Discharging to lower voltages
may damage the cells
40
• Stopping the test at
completion of the time or
capacity does not fully test the
battery
Analysis & Replacement Criteria
• If at 85% of service life , delivers
100% capacity or greater of the
manufacturer’s rated capacity,
and has shown no signs of
degradation:
• performance testing at two-year
intervals instead of 1-year
intervals
• Until the battery shows signs of
degradation
41
• Degradation:
• Capacity drop>10% from previous
performance test
• Below 90% of the manufacturer’s
rating
• Replacement: at 80% Capacity
Results and Report Review
42
Report Review
• Well documented report
•
•
•
•
•
•
•
•
•
•
43
Site information
Battery information
Installation date
Battery temperature
Capacity calculation method
Temperature correction
Voltage plot
Float and open circuit voltages
Individual cell voltages
Pause duration
Discharge Results
44
Test Pauses
45
Individual Cell Voltage (ICV)
• Not all cells discharge equally
• The deeper they discharge, the
faster the voltage will drop
• Some cells will discharge
beyond the individual end of
discharge voltage before the
overall voltage reaches end of
discharge level
• Can lead to polarity reversal
(Lead Acid)
46
• Continuous measurement of
each cell
• Helps to identify if a reduced
capacity is due to a few cells or
a general battery issue
Individual Cell Voltage
47
Summary
• Battery load testing is the only
proven method to accurately
measure the capacity and
determine the SOH
• Resource/Time demanding
• Involves careful preparation and
logistics
• Test is detailed in IEEE Std.
450, IEEE Std. 1188, IEEE
Std.1106
• A great amount of information is
logged during the test,
especially if individual cell
voltages are recorded
• Analysis of the test goes beyond
the % percentage capacity
48
Testing Tools
49
Torkel900
• Dynamic discharge
technology – Full power at all
voltages
• Battery voltage 7.5 V to 500
• Power 15 kW (max)
• Load patterns
• Constant current
• 0.1 to 220 A*
• Constant power
• 10 W to 15 KW
• Constant resistance
• 300mW to 3 kW
50
Multiple configurations
51
Multiple configurations
52
Extra Loads
53
Battery Voltage Monitoring (BVM)
• Automatic battery cell voltage
measurements during
capacity tests
• “Daisy-chain” design allows
expandability up to 2x120
cells
• Voltage ranges 0 – 20 V DC
• Battery string voltage 300 V
DC (max per loop)
54
Battery Voltage Monitoring (BVM)
55
Battery Voltage Monitoring (BVM)
56
Battery Voltage Monitoring (BVM)
57
Questions?
58