BATTERY ENCLOSURE
DESIGN - AS/NZS 4509
Applicable Standards
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Building Code of Australia
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AS/NZS 3000 Australian wiring rules
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AS 3011 Parts 1&2 Secondary batteries installed in buildings
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AS 2676 Parts 1&2 Installation and maintenance guide secondary
batteries in a building
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AS 4086 Secondary batteries for use with stand-alone power systems
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AS/NZS 4509 Parts 1 & 2 Stand alone power systems
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AS 3947 Low Voltage Switch gear and fuse disconnectors
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AS 3439 Type Tested Switch gear assemblies
Building Code of Australia
V1 Section C2.12:
Separation of equipment
Batteries installed in buildings Class 2-9 applies to:
Over 24V 10 Ah
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Requires FRL fire rating construction separation not
less than 120/120/120.
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F – Structural Adequacy
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R - Integrity
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L - Insulation
BCA V2 Class 1 &10 Buildings
Detached home - no mention of secondary
battery provisions
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Secondary batteries not an integral part of
detached housing design except for remote power
systems.
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BCA V1 identifies problems with secondary
batteries in buildings Class 2 -9
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battery back-up grid connected in detached
houses is reasonable that the requirements of V1
should be considered for Class 1 buildings
AS/NZS 3000 Wiring Rules
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Wiring rules for electrical installations and a
requirement of AS/NZS 4509,
AS 2676 and AS 4086
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All electrical work associated with a battery
installation must comply with these
Standards
AS3011 Secondary batteries
installed in buildings
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Readily accessible
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Battery accommodation – lockable, well ventilated
room, enclosure or restricted area
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Structurally adequate for the weight of the batteries
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DC switch boards should be located externally or
segregated from the battery accommodation
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Batteries – no exposed live parts
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Battery cables – flexible, clearly identified and rated
for voltage and fault current of battery
Battery requirements
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Overcurrent protection – HRC fuse or circuit
breaker in all unearthed battery cables of a fault
current capacity equal to or exceeding the fault
current of the battery
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Switch gear – rated for d.c. operation and where
the fault level of the battery exceeds 20kA form 4 segregation is required
Battery requirements
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Battery voltage – switches or links are required to
limit the battery voltage to less than 120 V d.c. for
maintenance. Unearthed batteries above 120 V
require earth leakage detection
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Warning signs – required for fire, explosion, acid
burn, battery voltage, battery capacity, start up and
shut down procedures for the battery system
Typical gel battery fault levels
Sonnenschein A600 Solar to IEC 896-2
Type of cell
Short Circuit Current
OPzV 4/295
2215 Amps
OPzV 6/625
4205 Amps
OPzV 8/1130
6795 Amps
OPzV 12/1960
10480 Amps
OPzV 24/3920
20970 Amps
•  AGM fault current normally 50% higher than gel
•  If battery data is not available AS 2676 suggests:
35 times C3 to calculate the fault current
•  35 x 750Ah @ 3hr rate =
22kA
Typical flexible cable fault levels
Cross Sectional Area
Short Current (1 sec)
90°C
110°C
10mm²
1,430 A
1,320 A
25mm²
3,575 A
3,300 A
50mm²
7,150 A
6,600 A
70mm²
10,010 A
9,240 A
150mm²
21,450 A
19,800 A
Battery cables must be resilient to sulphuric acid
and protected against mechanical damage
Battery overcurrent
protective devices
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HRC fuses and circuit breakers rated for d.c.
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at the battery voltage
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fault current capacity = > fault level battery
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values clearly stated on the device
or confirmation in writing obtained
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polarised d.c. circuit breakers should NEVER be
used for this purpose
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some HRC fuses and circuit breakers rated for a.c.
operation may not be suitable for d.c. applications
Ventilation
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adequate ventilation requirement of any battery
installation for the dispersion of hydrogen gas and
cooling of the battery
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hydrogen levels must not exceed 2% by volume
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vents should be located at highest point of battery
accommodation
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Calculations provided in AS 2676 & AS 4086
Ventilation
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Cooling the battery may be achieved by natural
convection or forced ventilation.
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As a general rule every 10°C above rated battery
temperature will halve the battery life.
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The battery manufacturer or AS 2676 should be
consulted for the minimum air flow required to
adequately cool the battery.
Ventilation
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vented lead acid battery in equalise charge per
kWh of battery capacity requires 0.5m³ per hour of
airflow
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based on a convection air speed of 0.1m/sec will
require a ventilation opening of 15cm² and half of
this value for VRLA batteries
AS 2676 and AS 4086
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Standards refer to specific details for the
installation and maintenance of secondary
batteries in buildings and compliance is referred to
in AS 3011
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Standards should be read carefully and in
conjunction with AS 3011
AS/NZS 4509.1 – Safety
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Batteries should not be housed near combustible or
flammable materials, spark or heat sources
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Safety signs should be positioned in clear view of the
batteries
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Battery enclosure must be designed to prevent entry
by children, be vermin proofed and display the
appropriate safety and warning signs including shut
down procedures
AS 3947 & AS 3439
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AS 3947 and AS 3439 are references for appropriate
switch gear to be used in battery installations
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AS 3947 refers to low voltage fuse switch
disconnectors no reference for use in DC circuits?
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AS 3439 is the standard that will be used for
installations in excess of 20kA requiring form 4
segregation
Thank you for your indulgence and I hope
this information may be of some use.
Cheers,
Warren Christensen - Powersafe Solar
warren@powersafesolar.com.au