In this informative webinar, Andrew Sagl of Megger presents an overview of the various battery testing technologies available as well as how to properly maintain VRLA and VLA batteries.

1. Battery Technology and Maintenance 101
Presented by: Andrew Sagl

2. 2
Agenda
 Types of Lead Acid Batteries
 Battery Applications
 Battery Failure Modes
 Battery Maintenance
 Maintaining VRLA Batteries
 Maintaining VLA Batteries
 Testing Parallel Strings

3. 3
Battery Types
 Primary Cells – These are non-
rechargeable batteries. These
include the standard Alkaline
battery and Lithium batteries.
 Secondary Cells – These are
the re-chargeable batteries.
These include lead acid
batteries, NiCD as well as
Lithium Ion.

4. 4
Secondary Batteries
 Cyclic Batteries – These are
batteries that are used on a
regular basis. The most
common of these is auto-motive
batteries or portable battery
operated devices.
 Standby Batteries – These are
batteries that remain charged
but are not used unless needed.
• Sub-stations (Relays)
• Telecom (Communication)
• Data Centers (UPS)

5. 5
Battery Types
 Lead-acid - can come in
several different chemistries,
however regardless of
chemistry they will all be either
flooded cell (VLA) or sealed
(VRLA) cells.
 Flooded cells (VLA) – will
vent hydrogen as they
discharge. This will lead to
water loss in the electrolyte.
Therefore flooded cells need to
have distilled water added to
the electrolyte periodically.

6. 6
Battery Types
 Sealed cells - (Valve Regulated
Lead Acid VRLA) often referred to
as “maintenance free batteries”,
will recombine the hydrogen from the
discharge reaction back into the
electrolyte. This means the operator
does not need to periodically add
water.
 However if they do overheat the
internal hydrogen gas pressure will
increase. If it gets too high the valve
will vent the gas.
 This will lead to water loss, which
cannot be replaced.

7. 7
Battery Types
 VRLA oxygen recombination
 In VRLA batteries, oxygen
released from the positive plate
travels to the negative plate where
it combines with hydrogen to form
water. It is because of this
recombination that VRLA batteries
remain moist and don’t have to be
periodically filled with distilled
water.
 Not 100% efficient

8. 8
Battery Applications
 Batteries are not created
equally.
 Different Applications require
different battery designs.
 Plate design and surface
area are designed for
specific applications.
 Different applications can
require different chemistry
batteries.

9. 9
Battery Applications
 The more plate surface area
that is available the more
capacity a battery will have
and the more current it can
deliver.
 Batteries in cyclic
applications will typically
have less plates but they will
be thicker.
 Thicker plates allow them
to better deal with the heat
generated by repeated
charge and discharge
cycles.

10. 10
Battery Applications
 Lead antimony batteries will
be stronger. This helps deal
with the heat generated from
repeated charge / discharge
cycles.
 Antimony is not good for
stand by applications
because antimony batteries
will suffer from antimony
poising when left at float.
 Lead Calcium batteries will
deal with float applications
better because they do not
suffer from antimony
poisoning.
 Lead Calcium is not as
strong as lead antimony so
it does not deal with
repeated charge and
discharge cycles as well as
lead antimony.

11. 11
Battery Applications
 Cyclic Batteries – These are batteries
that are used on a regular basis. The
most common of these is auto-motive
batteries or portable battery operated
devices, such as forklifts and golf
carts.
•Lead Antimony Design
•Stronger plates good for the repeated heating effects of charge /
discharge cycling.
•Not good on long periods of float, which cause antimony poisoning.
•Thicker Plates
•More material to withstand corrosion

12. 12
Battery Applications
 SLI Batteries – (Starting Lighting
and Ignition) Batteries. These are
a type of cyclic batteries used
mainly in automotive applications.
•Lead Antimony Design
•Stronger plates good for the repeated heating effects of charge / discharge cycling.
•Not good on long periods of float, which cause antimony poisoning.
•Many Thinner Plates
•Maximizes surface area in order to deliver high volumes of current in a small period
of time.
•Only meant to be discharged a small amount. Not good for deep discharge cyclic
applications.

13. 13
Battery Applications
 Stationary Batteries – These are
batteries that remain charged but
are not used unless needed.
• Sub-stations (Relays)
• Telecom (Communication)
• Data Centers (UPS)
•Lead Calcium Design
•Good on long periods of float because NO antimony poisoning.
•Not good for the repeated heating effects of charge / discharge cycling.
•Plate thickness dictated by capacity
•More surface area = more capacity.
•Thick plates = longer life span.

14. 14
Failure Modes

15. 15
Failure Modes
 Positive Grid Corrosion
 Normal failure mode in flooded lead-
acid (VLA) batteries
 Lead alloy turns to lead oxide.
 Plates grow
 Designed into batteries
 Acceleration due to:
• Overcharging
• Excessive cycling
• Excessive temperature
 Increase in internal impedance

16. 16
Failure Modes
 Shedding
 Sloughing off of active material from plates into white lead sulfate.
 Small amount is normal
 Excessive build up can cause plate shorts
 Due to overcharging and / or excessive cycling.
 Only in flooded batteries.

17. 17
Failure Modes
 Sulfating
 Active plate material turns to lead
sulfate.
 Lead Sulfate = Inactive material
 Occurs in both Flooded and VRLA
batteries
 Natural process during discharge.
 Recharging reverses the process.
 Undercharging causes sulfate
crystals to form on the plate
surfaces.

18. 18
Failure Modes
 Sulfating
 Sulfate crystals that harden over a
long period of time.
 These will not go back in solution
when proper voltage is applied.
 Decreases total active
material/capacity
 Result in a permanent loss of
capacity.
 Increase in internal impedance

19. 19
Failure Modes
 Shorts
 Shorts can occur in both Flooded and VRLA cells.
 Hard shorts are typically caused by paste lumps pushing through
the matte and shorting out to the adjacent (opposite polarity) plate.
 Soft shorts on the other hand, are caused by deep discharges.
 When the specific gravity of the acid gets too low, the lead will
dissolve into it. Since the liquid (and the dissolved lead) are
immobilized by the glass matte, when the battery is recharged, the
lead comes out of solution forming dendrites inside the matte.
 In some cases, the lead dendrites short through the matte to the
other plate.

20. 20
Failure Modes
 Dry out (Loss of Compression)
 VRLA batteries only (Most common failure mode)
 Dry-out is a phenomenon that occurs due to excessive heat, over
charging can cause elevated internal temperatures as well as high
ambient (room) temperatures.
 At elevated internal temperatures, the sealed cells will vent through
the PRV.
 When sufficient electrolyte is vented, the glass matte no longer is in
contact with the plates, thus increasing the internal impedance and
reducing battery capacity.

21. 21
Failure Modes
 Thermal Runaway
 Thermal run-away is when a battery internal components melt-down
in a self-sustaining reaction.
 Failure mode VRLA batteries
 Can end in complete and catastrophic failure
 Primarily due to oxygen recombination cycle
 Thermal run-away is relatively easy to avoid, simply by using
temperature-compensated chargers and properly ventilating the
battery room/cabinet.
 Temperature-compensated chargers reduce the charge current as
the temperature increases.

22. 22
Failure Modes
 Thermal Runaway
 Flooded cell allows gas to escape
 VRLA recombines oxygen and
forms water
 Reaction produces heat
 Due to:
• Overcharging
• High ambient
• Low air flow
• High float voltage
 Heating is a function of the square
of the current

23. 23
Failure Modes
Watts Lost = (Current)2 (Resistance)
 Loose Connections
 Frequent Problem all battery types
 Easily found with resistance measurement
 High resistance = elevated temperature = higher resistance
 When serving load high temperatures can melt lead posts

24. 24
Battery Maintenance

25. 25
Battery Maintenance
 No single test tells the whole story
 Determine condition
 Where condition is headed
 How fast
 Don’t find out during an outage that your battery failed
 Gather as much test data as possible

26. 26
Battery Maintenance
 Visual Inspection
 Float Voltage
 Float Current
 Ripple Current
 Specific Gravity
 Temperature
 Discharge Testing
 Ohmic Testing
 Strap Resistance

27. 27
Battery Maintenance
 Visual Inspection
 Check entire system
 Battery Electrolyte Level (Flooded Batteries)
 Ventilation system, floor & room clean
 Battery support system
 Check batteries for cracks, leaks and deformation
 Strap corrosion
 Record information
• Visual inspection will locate such things as cracks, leaks and corrosion
can be found before they become catastrophic failures. However, visual
inspection tells us nothing about the strings State of Charge (SOC),
capacity or State of Health (SOH).

28. 28
Battery Maintenance
 Float Voltage
 Measure across each cell
 Measure at posts
 During float conditions
• Not during discharge or
recharge
 Compare float voltage to
manufacturers recommendation

29. 29
Battery Maintenance
 Float Voltage
 Applied voltage to cell from charger
 Different voltages for different chemistries
 Low float voltage > not fully charging
• Can’t supply full capacity
• Plate Sulfation
 High float voltage > Over charging
• cooks the battery
• higher temperature
• Grid corrosion
• Thermal runaway
• Dry-out
■ Float Voltage will tells us if something is wrong but it will not tells us anything
about SOC, Capacity or SOH.

30. 30
Battery Maintenance
 Float Current
 Kirchhoff current law
 Measure anywhere in the string
 Usually low value
 Measure during float conditions
 Not during discharge or
recharge
 Increase in float current
precursor to Thermal Run-away
VRLA

31. 31
Battery Maintenance
 Float Current
 Current through each cell
• Interaction between float voltage and internal resistance
 Supplied by charger
 Electrochemical process reversed
• Lead sulfate on plates converted to sulfuric acid and active material
 High float current precursor to thermal runaway
• Short circuits
• Ground faults
• High float voltages
■ Float Current will tells us if something is wrong but it will not tells us anything
about SOC, Capacity or SOH.

32. 32
Battery Maintenance
 Ripple
 By-product of charging system
 Design, quality and age dictate
 Internal heating of battery and overcharging
 No more than 5A for every 100Ah

33. 33
Ripple Frequency
 When examining ripple
current we need to examine
both the amplitude and the
frequency of the ripple.
 High frequency ripple above
several hundred Hz has
limited effects on lead acid
batteries.
 Low frequencies ripple can
have significant effects.

34. 34
Ripple Frequency
 Low frequency ripple will
cyclically raise and lower the
float voltage.
 This can cyclically raise the
float voltage above the
maximum rating of the
battery.
 This can cyclically lower the
float voltage below the open
circuit voltage of the battery
 This leads to repeated
heating and sulfation of the
battery.
 Lowering its life span.

35. 35
Battery Maintenance
Volume
Mass
Density 
 Specific Gravity
 Ratio of density of liquid with
respect to density of water
 How much sulfate is in
electrolyte – lead acid
 Gives SOC but not Capacity
or SOH.
 Density is temperature
dependent

36. 36
Battery Maintenance
Temperature Effects
50
60
70
80
90
100
110
120
47 62 77 92 107
Temperature (F)
Capacity(%)
0
5
10
15
20
25
30
BatteryLife(yrs.)
% Capacity Life (yrs.)
 Temperature
 High temp = short life
 Low temp = low capacity possible damage
 10 °C rise = ½ life

37. 37
Battery Maintenance
Partial Load Test
1.5
1.7
1.9
2.1
2.3
0 5 10 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240
Time (min)
VoltsperCell
Passes Better Failure
 Discharge Testing
 Single absolute test
 Complexity & cost
 Acceptance Test
• Beginning of life based on design capacity
 Performance Test
• After two or three years when new then
every five years
• Based on design capacity also
 Service Test
• As needed to determine if battery will
support existing load
 Discharge Testing is the only test that will
determine the capacity of the string, but not
necessarily the SOH.

38. 38
Ohmic Testing
Ascending Impedance with Corresponding End Voltage
0
0.25
0.5
0.75
1
1.25
1.5
1.75
2
2.25
2.5
Impedance(mOhms)&EndVoltage
Imp 0.27 0.27 0.27 0.56 0.61 0.63 0.65 0.68 0.71 0.72 0.74 0.75 0.79 0.8 0.82 0.84 0.89 0.9 0.91 0.94 0.96 1.17 1.19 2.1
End V 2.03 2.04 2.03 1.98 1.97 1.94 1.9 1.91 1.88 1.89 1.9 1.89 1.89 1.84 1.82 1.84 1.81 1.84 1.8 1.73 1.82 1.74 1.33 0.1
Cell # 11 15 16 3 18 22 13 24 10 14 23 20 5 9 6 4 21 8 1 12 2 17 7 19
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
 Provides SOH rather than just SOC
 As the battery ages and sulfates the impedance of the battery
will increase as the capacitance decreases.

39. 39
Ohmic Testing
 There are different types of ohmic tests.
 Resistance – Measures only the resistive value of a battery,
The battery also has capacitive and inductive values as well.
 Conductance – (Actually Admittance) This is the reciprocal of
impedance.
 Impedance Testing – Measures the resistive, capacitive and
inductive qualities of the battery.

40. 40
Ohmic Testing
 Impedance testing has a distinct advantage over resistive type testing. When
we look at a schematic representation of a battery there are more than just
resistive components to that battery. There are also capacitive and inductive
characteristics.

41. 41
Ohmic Testing
 AC impedance testing will detect signs of battery aging sooner than purely
resistive measurements.
 Batteries are NOT resisters.
 Batteries contain both an electrolyte liquid and solid plates.
 When liquids and solids meet they create a double layer effect. In essence
this is a capacitor.
 As a battery ages the capacitance of the double layer will change well before
the resistance of the plates.
 Resistive testing ignores the capacitive double layer effect.

42. 42
Ohmic Testing
 Ohmic testing is not an absolute test. The
measured value is not compared to a standard
known good value to determine if the battery is
good or bad.
(Ohmic testing is NOT a GO / NO GO Test)
Ohmic testing is a relative test. The measured value is
compared to the previously measured value to see how much it
has changed. The percentage change indicates how much the
battery chemistry has changed; which is an indicator of the
batteries State Of Health. (SOH)

43. 43
Ohmic Testing
 Different instruments will measure
different values.
 Various ohmic test instruments
operate at different frequencies
and currents.
 Different test frequencies will
provide different ohmic values for
the same cell.
 Some test currents are too low to
get repeatable results on larger
batteries.
𝑍 = 𝑅2 + 𝑋𝑐
2
𝑋𝑐 =
1
2𝜋𝑓𝐶
Different frequency cause
different reactive capacitance
values which cause different
impedance values.

44. 44
Ohmic Testing
 Since you can get different measurements with different
models of instruments we can see that ohmic testing is a
relative test NOT an absolute test.
 We do not test against an absolute value. We test and
compare that data to a previous test result.
 Repeatability is the KEY parameter.

45. 45
Battery Maintenance
 Inter-cell Resistance
 If the torque not sufficient
this will cause a higher
resistance causing a voltage
drop that causes heat.
 Measure across strap
• Not on Strap
• On Post

46. 46
Battery Maintenance
 When testing a strap with a DC low
resistance ohm meter the
measurement must be taken in both
directions.
 This is because there is DC current
already going through the strap
from the charger.
 One direction will be higher than the
other. Therefore both directions
must be measured and an average
of both taken.
 A low frequency AC measurement
does not require dual
measurements.

47. 47
Battery Maintenance
 Strap measurement are also
relative measurements just like
battery measurements.
 Different frequencies will give
different values.
 Different model duplex leads can
give different values due to different
current densities between the tips.
 IEEE states that when a strap
measurement deviates by 20% or
more then that strap should be
addressed.

48. 48
Maintaining VRLA Batteries

49. 49
Maintaining VRLA Batteries
 Failure Modes
• Dry out
• Thermal Runaway
• Sulfating
• Soft shorts / deep discharge
 Tests to Run
• Inspection
• Float Current
• Ripple Current
• Ohmic Testing
• Inter-cell strap measurements
 How often
• Quarterly

50. 50
Performing an Ohmic Testing
 When performing battery ohmic measurements a certain test methodology
needs to be followed. This is because battery ohmic measurements are in
micro-ohms.
 Many factors can affect these measurements. For example, the following
criteria will affect the reading taken to various degrees.
• Cell Type
• Battery Charge
• Temperature
• Make and model of instrument being used.
• Probe Type
• String length and configuration.
• Load
• Charger
• Where the measurement is taken on the battery.

51. 51
Ohmic Testing
 In order to maintain good
repeatability a certain test
methodology must be performed.
• Battery string needs to be fully
charged.
• The user must use the same make
and model instrument
• The same probe type needs to be
use from one test to another.
• The measurements need to be taken
at the same point. (Posts are the
preferable location)

52. 52
Ohmic Testing
 Establishing a Baseline
 A baseline is a reference value (starting value) used to
determine the amount a batteries chemistry has changed over
time.
 Baselines should NOT come from battery manufacturers
• You do not know what equipment they used for testing.
• The batteries they test are stand alone.
• The battery is not in your string
• The battery is not connected to your charger
• The battery is green. Has not gone through formation.

53. 53
Ohmic Testing
 Test Data can be
analyzed in 3 ways.
 Cell Average:
 Ohmic values of each cell
comprising the string are
compared to the strings
average ohmic value.
This is useful in
identifying weak cells
within the bank. If the majority of cells in the bank are in poor
quality then the string average will be poor.
This method will find poor cells but not
necessarily a weak string.

54. 54
Ohmic Testing
 Baseline Reference:
 Comparison of
ohmic values to
baseline values.
 Comparing the string
average to the
baseline helps
establish the overall
health of the string.
If all the cells have aged at the same rate
then the cell average will look good, while
the entire string has aged.
Comparing the values to an initial baseline
value shows how much the sting has aged.

55. 55
Ohmic Testing
 Impedance Trending:
 Trending of ohmic
values and observing
the percentage of
change from one test
period to the next test
period is ideal for
establishing an
approximate rate of
aging. This data is
useful in forecasting
future needs.  If a battery is aging faster than expected then this could be an
indication of a possible issue.
 Wrong type of battery for application
 Environmental issues
 Maintenance issues
 Poor quality battery

56. 56
Maintaining VLA Batteries

57. 57
Maintaining VLA Batteries
 Failure Modes
• Positive Grid Corrosion
• Shedding
• Sulfating
• Soft shorts / deep discharge
 Tests to Run
• Inspection
• Float Current
• Ripple Current
• Ohmic Testing
• Inter-cell strap measurements
 How often
• Bi Annual (6 Months)

58. 58
Maintaining VLA Batteries
 Large high capacity VLA batteries
have a larger plate surface area to
support the higher capacity.
 Since the batteries have more plate
surface area the impedance of the
cells is lower.
 When performing ohmic testing the
test current must be high enough to
get repeatable results and
overcome any signal to noise ratios.
 Higher capacity batteries require
higher test currents for repeatable
results.
For example: If the battery under test is
500uΩ and the test current is only
100mA then the voltage drop across
the battery is only 50uV. A small
amount of noise can cause non
repeatable results.
𝑉 = 0.1𝐴 ∗ 0.0005𝛺
𝑉 = 𝐼 ∗ 𝑅
𝑉 = 0.005

59. 59
Parallel Strings
 VLA batteries typically fails in a
shorted mode. Due to plate
corrosion. Current can still pass
through the string.
 VRLA batteries typically fail in an
open mode. Dry-out. Current
cannot pass through the string.
 To increase reliability VRLA
batteries are typically assembled in
parallel string configurations.

60. 60
Parallel Strings
 When testing a series string the test
current only goes through the
battery under test.
 It is the only low resistance path for
the test current.

61. 61
Parallel Strings
 When testing a parallel string the
test current goes through the
battery under test as well as the
parallel path.
 The parallel path offers another low
resistance path.

62. 62
Parallel Strings
 If the impedance of a battery
changes due to changes in
the cell it will change the
current draw through the
parallel path.
 This will change the current
through the battery being
tested.
 This will lead to all the
batteries showing altered
impedance values.
 Cannot locate the poor cell.
 Typically you must segment
the parallel string.

63. 63
Parallel Strings
 By using a CT to measure
the “escape” current in the
parallel path the ohmic
tester can determine the
correct amount of current
going through the battery
being tested.
 No false readings
 No segmentation required.

64. Questions or Comments?
Email Nicole VanWert-Quinzi
nicole.vanwert@Transcat.com
Transcat: 800-800-5001
www.Transcat.com
For related product information, go to:
www.Transcat.com/Megger