Battery System Testing: A Comprehensive Guide

Purpose and Scope

Batteries play a crucial role in providing an uninterrupted DC supply for protection relays, communications, and plant trip/close circuits. Common battery bank voltages include 24V, 32V, 48V, and 110V. To prevent unexpected failures and ensure reliability, batteries must be tested both during pre-commissioning and at regular intervals thereafter. Initial testing should occur prior to commissioning, followed by a test after 2 years. Subsequently, an internal resistance test is recommended annually, with a discharge test every 5 years. If a discharge test indicates that the battery is nearing the end of its life, annual testing is advised.

Australian Standards applicable to batteries

AS 4086.2-1997 Battery Maintenance
IEEE 450-2010 Recommended Practice for Maintenance, Testing and Replacement of Vented Lead-Acid Batteries for Stationary Applications

Specialized test equipment that may be required

Multimeter
Battery Impedance Tester – Hioki 3554
Battery Discharge Tester – Megger Torkel 930, Torkel 950 or DV Power BLU200

Safety Notes for Battery System Work

When working with battery systems, adhering to safety protocols is essential to prevent hazards and ensure proper handling. Follow these guidelines to maintain a safe working environment and protect both personnel and equipment.

Hazard Assessment: Identify and assess any hazards associated with the worksite prior to commencing activities. Implement and document appropriate control measures.
Manufacturer’s Instructions: Always adhere to the manufacturer’s guidelines for battery operation and maintenance.
Ventilation: Operate batteries in cool, well-ventilated areas. If a ventilation fan is available, run it for 30 minutes before starting work.
Tool Safety: Minimize short circuit risks by using insulated tools when working with battery terminals.
Hot Work Precautions: If performing hot work near batteries, create a nitrogen barrier between the batteries and the atmosphere. This can be achieved by covering the batteries with a fire blanket and injecting nitrogen underneath.

Information to be recorded

Battery Manufacturer
Battery Model Number
Battery Voltage
Battery Rating AH
Charger Details

Work procedure

Plant inspection

Inspect the batteries for any sign of damage such as corrosion, warping, residue on external surface and terminal lifting.

Inspect external surfaces and ensure clean and dry.

Inspect mounting frame for any damage, corrosion or deterioration

Check all connections for adequate labelling. The connections should be unambiguous, legible and adequately marked.

When commissioning, ensure the installed batteries match the design specifications.

Note for Brownfield Sites

When performing maintenance on brownfield sites, remember that isolating the charger might disable the protective tripping system. Therefore, it is advisable to conduct tests with equipment loads turned off and minimize the time required for testing. Utilize a temporary battery bank or switch to an existing secondary battery bank if available.

Pre-test checklist

Record all details as required and include charging current and voltage. If possible, check to see that each battery is the same model and note any variances.

Record battery bank voltage and individual battery voltages before testing commences

Impedance Tests

Internal impedance measurement of each battery is crucial, as it correlates with voltage decay over time. Compare the measured impedance with the internal resistance value provided by the manufacturer for a new battery. A battery should be replaced if its measured resistance is more than twice the manufacturer’s specified value.

Use a Hioki 3554 for internal resistance testing, the following instructions are for using this particular instrument.

Set the appropriate resistance and voltage measuring range
Use the zero adjustment feature for accurate readings
Make sure the polarity of the leads are correct when testing

Refer to the manufacturers’ manual for more detailed instructions, or if using a test unit other than the Hioki 3554. Record results on an appropriate form.

Discharge Tests

Perform a discharge test according to the battery bank’s rated ampere-hour capacity. Record the load used, the duration of the test, and the final voltage of each battery. The manufacturer should specify the acceptable voltage post-discharge. If not available, use 75% of the rated battery voltage as a guideline.

Example Table: The table below, provided by a manufacturer, outlines the ampere rating over time until the cell reaches the end voltage. This is a sample only, and you should obtain the specific capacity rating for the battery being tested.

End Volt. /Cell	Model	8 h Ah Ratings	Nominal rates at 25 ° C (77° F) Amperes (including connector voltage drop)
End Volt. /Cell	Model	8 h Ah Ratings	1h	2h	3h	4h	5h	6h	8h	10h
1.75	DCU/DU-9	100	52	34	26	21	18	15	12	10
	DCU-DU-11	120	66	41	30	25	21	18	15	13
	DCU/DU-13	150	78	50	38	31	27	23	19	16

Isolate the battery bank and set up a variable load across the battery bank terminals, with a voltmeter and ammeter. This will typically be in the form of a battery discharge unit such as a Torkel. The load needs to be varied to maintain a constant current as per the manufacturers’ specs/nominal current.

For example, if testing a DCU/DU-9 for 5 hours, maintain an 18A load for the duration of the test.

Once the load is connected, start timing and continue to maintain the required current.
Record the start battery voltage. Take 3-5 voltage measurements during the test and record the end voltage.
Any Battery cells that display a reduced voltage before the end of the test can be considered to have a reduced capacity and may need replacement.
Disconnect test equipment and return the battery bank to normal condition with all connections remade.
Turn the battery charger on and note if the charger goes into boost mode. This is a functional operation check when batteries discharge below a specified level. Allow the charger to return the battery to float charge as per manufacturers’ specifications.

Post-Test Checklist

Ensuring safety during and after battery system testing is crucial for maintaining operational integrity and preventing accidents. The following safety notes will guide you through the essential post-test procedures to ensure a safe and effective battery maintenance process.

Record Keeping: Document both the battery bank and individual cell voltages as they are left.
Terminal Inspection: Ensure battery terminals are tight, but avoid overtightening.
Charger Status: Confirm that the battery charger is online and charging.
Cleanup: Verify that all tools and equipment have been removed from the work area.

Complete pre-commissioning checklist

Ensure test sheet filled out, signed and outline any action items.
Ensure connections are snug, and battery bank is free of tools.
Ensure battery charger is switched on.
Final visual inspection.
Note any batteries that have failed test.
Note recommended date of next test.

By following these guidelines, you can ensure effective and safe battery system testing, contributing to the reliable operation of your electrical systems.