I hope that this - Go-NPSgo-nps.com/wp-content/uploads/2018/01/VRLA-OM.pdf · The three C’s: Good C harging 24 PSOC cycling causes the a migration and coarsening of PbSO 4 crystals

I hope that this second part

will be interesting too!

2

The key parts of an VRLA Lead Acid battery

3

How to

• select and size a VRLA stand-by battery

• inspect the incoming VRLA battery

• install connectors, cables and sensors

• operate the VRLA battery

• monitor the VRLA battery

4

What is a key VRLA/AGM feature?

VRLA

AGM

Internal

oxygen

recombination

5

The valve of a VRLA cell

6

VRLA

AGM

What is a key VRLA feature?

Fragile

charge balance

due to

internal oxygen

recombination

100mA 100mA

4mA ?1mA ?

2mA ?

7

1mA ?

• How to specify a stand-by VRLA battery

Applicable standards (suggested)

8

• How to specify a stand-by VRLA battery

Applicable standards (suggested)

9

• How to select and size a VRLA battery

batteries experience

- frequent and irregular discharges

- irregular recharges (A and duration)

- irregular full charges (PSOC operation)

- high ambient temperatures

- vandalism and theft

- difficult access for R&M

- remote site operation

- weight and size constraints

10

• Cell cycling or the rebuilding a brick wall blindfolded 1000 times

11

100%PbO2

70%PbO2

30%PbSO4

<100%PbO2

g.Ah-1

g.cm2

g.cm3

Frequent cycle service requires adaptation of cell design

Cycle life test to 40% DOD of C10

Float voltage recharge

12

Find optimum cost per day of use DOD/day – days life – cost battery

13

VRLA

Select units based on pivot value

“cycles to 100% DOD”

14

• Ah load capability needed

• days of life desired

• cost of cycle

• operating temperature

• offered cell weight

• unit voltage (12V/6V/2V)

• size and layout

• charge condition

• warranty conditions


Design choices made

Frequent cycle service requires adaptation of cell design (more lead, better grid design)

HDT temperature

125°C

15

No hidden clauses and conditions

The “fine print” contract

16


1.90

1.95

2.00

2.05

2.10

2.15

2.20

1 3 5 7 9 11 13 15 17 19 21 23

OC voltage incoming 2V

48V set 1

48V set 2

2V cells – incoming inspection for OCV

• How to inspect the incoming VRLA battery

• Check for completeness of battery order

• Check for completeness of accessories

• Measure Open Circuit voltages

• Record ID numbers and date incoming

• Keep delivered battery batches together

17

• How to store the delivered VRLA battery

• Store dry and as cool as possible

• Keep delivered battery batches together

• Implement First-in First-out stock keeping

• Do not mix suppliers and types

• Recharge when units at ≈2.04 Vpc!

• Self-discharge rate 2-3% per month at 20°C

18

Damages due to “over-storage”

• Excessive abnormal grid corrosion

• Growth of large lead sulfate crystals

• AGM pore blocking with sulfate

• “Leading-through” at the next charge

OC corrosion

CC corrosion

d

• How to install connectors, cables and sensors

• Have tools ready (hex-keys, torque wrench, voltmeter)

• To avoid dangerous shorts use only insulated tools

(IEC 60900:2004)

• Take off rings, metallic wristband watches, pendants

• Wear protective goggles

• Watch out when lifting heavy batteries

19

• How to install connectors, cables and sensors

• Step 1 Check voltage of each cell or monobloc supplied (V>2.04Vpc)

• Step 2 Switch-off rectifier/charger according to supplier instructions

• Step 3 Place all cells or monoblocs onto rack or tray

• Step 4 Check for proper polarity sequence + - + - + - and apply ID#

• Step 5 Take away terminal cover and install connectors

• Step 6 Tighten with proper torque terminal screws and replace cover

• Step 7 Verify for proper voltage and polarity of the string

• Step 8 Connect cables and voltage sending leads to rectifier/charger

and tighten screws

• Step 9 Switch on the rectifier according to supplier instructions

• Step 10 Verify cooling, ventilation and ventilation openings

• Step 11 Verify string voltage when in constant voltage charge state

20

• How to operate the VRLA battery

The three C’s

21

Nurse

.....I need

some

good

care!

22

The three C’s: Good Charging

23

• Check string float voltage for proper setting

• Do not charge when battery temperature is >50°C

• Any unit floating below 2.16Vpc or 12.0V is in danger!


24

PSOC cycling causes the a migration and coarsening of PbSO4 crystals

which are then more difficult to retransform into PbO2 and can clog the AGM

PSOC = partial state of charge operation due to lack of charge ampere hours

Diluted electrolyte higher PbSO4 solubility

Remaining PbSO4 nuclei sites for further growth and coarsening

High temperatures higher PbSO4 solubility


Off-grid Diesel Gen based operation

• One-box-has-it-all solution

• 24/24h 7/7d supply of 1500W -48V DC

• Daily Diesel running time reduced from 16h to 8h

• Fuel consumption <16l/day – 2 months fuel on board

• 16h silent battery running time

• High rate charge back with 5.7KW and 2.37Vpc

• Full recharge each cycle

• 1100 cycles of estimated battery life

• Optimized battery cooling and integrated

Eltek-Valere controller

25

• Keep AC ripple to <5A (rms) per 100Ah as ripple current = heating current

• Avoid DC ripple due to equipment defects

• Boost charge with moderation (2.35Vpc - 8h)


26

• All VRLA cells and batteries emit hydrogen thus ventilate according

to IEC 62485-2 (2010)

• Hydrogen gives an explosive mixture from 4 to 75% vol/vol in air


27

IEC 62485-2:2010 IEC 62485-2:2010

28

IEC 62485-2:2010 IEC 62485-2:2010

29

• Poor RBS equipment design

• Sloppy installation team

• Battery overheating

• No hydrogen gas extraction

• Hydrogen explosion

• RBS cabinet destruction

1

2

H2

30

•

• Battery heating comes from polarization in Volt per cell x current flow

• Polarization is the difference, in Volt, between open and closed circuit voltage

• The difference develops from Ohmic losses (minor) and Electrochemical losses/resistances (mayor)

• In VRLA batteries the oxygen recombination , under float , is another heat source (0.1W/cell/100Ah)

The three C’s: Good Cooling

discharge

charge

31

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

0

100

200

300

400

500

600

700

0 100 200 300 400 500 600

Av

era

ge

ce

ll te

mp

era

ture

me

asu

red

in °

C

Inst

an

tan

eo

us

Wa

tt p

rod

uce

d

Charging time in minutes

Calculated instantaneous heat production in Watt and observed average cell temperatures during theIU 100A/56.88V - 8h charge based on assumed cell

polarization

heat produced

Average T° cells

no A/C cooling

31.0°

22.0°

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

0

100

200

300

400

500

600

700

0 100 200 300 400 500 600

Ave

rage

cel

l tem

pera

ture

mea

sure

d in

°C

Inst

anta

neo

us

Wat

t p

rod

uce

d

Charging time in minutes

Calculated instantaneous heat production in Watt and observed average cell temperatures during the

IU 100A/56.88V - 8h charge based on assumed cell polarization

heat produced

Average T° cells

with A/C cooling

27.3 °

30.5°

28.5°


32


Average T° = 33.3°C

f33.3°C = 1.777

31d x 1.777 = 55d at 25°C

Summing up each day’s factor

31d = 61d at 25°C

33


25°30°35°40°45°

Plastic softening

Plastic material propertyVicat temperature °C

HDT temperature °C

is life limiting through

AGM compression loss

34

• How to operate the VRLA battery

The three C’s: Good Caring

• Select reputable supplier

• Evaluate products offered, its design and application history

• Keep battery troubles data base up-to-date

• Keep battery clean and contacts protected

• Keep float voltage, impedance or conductance data at site

• Instruct and train battery maintenance staff

35

• How to monitor the VRLA battery

36


37


1.99

2.04

2.09

2.14

2.19

2.24

2.29

2.34

Cell float

voltage

1 3 5 7 9 11 13 15 17 19 21 23

11.50

12.00

12.50

13.00

13.50

14.00

14.50

1 2 3 4

Mo

no

blo

c f

loat

vo

ltag

e

Measure voltages

<2.18Vpc defect cell

2.20Vpc lower limit

2.25Vpc ideal

2.35Vpc wet cell?

0.07mV

√n

2.449/12V

1.732/6V

38


Measure temperature

Use thermal imaging

25°+-1°C max

cool cell = short?

hot cell = Ohmic?

hot cell = air flow

39


Measure float current

Clamp-on high resolution Amp meteror

Polytronics® Continuous Float Monitor

The float current, when fully charged,

should be less than

1mA per Ah C10 (100mA/100Ah)

40


Measure impedance or resistance

Midtronics, Alber, Hioki etc.

Proceed as follows:

• Install cell/monobloc

• Float for 6 months

• Measure individual mΩ or Siemens

• Record value on cell/monobloc

• Re-measure once a year

• Investigate if this value has changed

(increase/decrease) by more than 20%

41


No Yes

42

• How to monitor the VRLA battery Distribution of the conductivity (AC) of the 2CP300 monoblocs after 2588

and 3318 days of float operation

0

5

10

15

20

25

100

400

700

1000

1300

1600

1900

2200

2500

2800

3100

3400

3700

4000

4300

4600

4900

Conductivity in Siemens under float at 31°C

Num

ber

of unit

s per

cla

ss

Alloy 707 - 9 years

Alloy 720 - 7 years

Correlation of internal conductivity and 13 minute rate capacity of the two sets

of 2CP300 monoblocs after 7 and 9 years respectively

1000

1500

2000

2500

3000

3500

4000

4500

5000

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 120% 130%

Residual capacity after float service

Inte

rnal

AC

co

nd

ucti

vit

y in

Sie

men

s

707 alloy set after

9 years

720 alloy set after

7 years

Δ 15%

Δ 20%

Correlation of

conductivity (S) vs. capacity (Ah)

at UPS rate (15m)

43


Measure residual capacity

Last resort method

Proceed as follows:

• Select non-critical period

• Have power back-up ready

• Test only one string per year

• Start testing after 2-3years service

only or before end-of-warranty

• Discharge with user load

• Discharge to at least 50% d.o.d

• Use automatic voltage logging

• Recharge with auxiliary rectifier

44

45

46

47

Hello – Are you sleeping?

1) What is the purpose of the “Safety Valve” ?

2) Name Major Parts of a VRLA Battery ?

3) What are the important factors to consider in choosing a battery?

4) What are the 3 important C’s that you must not forget after this training ?


1) What is the purpose of the “Safety Valve” ?To release the excess gas build up in the battery during

overcharge condition


2) Name Major Parts of a VRLA Battery1 Positive Plates

2 Negative Plates

3 Electrolyte – Acid

4 Separator

5 Container

6 Safety Valve


3) What are the important factors to consider in choosing a battery?

1.Battery Material

2.Battery Manufacturer

3.Battery After Sales Support Service

4.Battery Type of Application

5.Battery Design and Sizing

6.Price – “Cheap ---cheap…..cheap,,,,,cheap”


4) What are the 3 important C’s that you must not forget after this training ?

Good Charging

Good Cooling

Good Caring

Documents

I hope that this - Go-NPSgo-nps.com/wp-content/uploads/2018/01/VRLA-OM.pdf · The three C’s: Good C harging 24 PSOC cycling causes the a migration and coarsening of PbSO 4 crystals