Megger’s applications engineer, Antony Wills, discusses the need for battery testing to ensure the resilience of mission critical facilities as sites cannot afford to become complacent.

Where the power supply is quite reliable, standby batteries sit unused for 99% of the time, leading to negligence around these forgotten assets. Yet battery failure is a leading cause of load loss. There are some myths and misconceptions in the market that need to be dispelled and the quality of testing still varies widely.

This article first appeared in ESI Africa Edition 4, 2018. You can read the full digital magazine here or subscribe here to receive a print copy.

There is a tendency to fit and forget batteries, but it is critical that your assets work when called upon, so testing is essential to prevent any costly downtime. Some people believe that batteries, that are advertised as being ‘maintenance-free’, do not need to be tested, but this simply means that you cannot perform maintenance on the battery – it can still fail before the end of its designed life. Battery capacity can drop significantly long before its calculated life expectancy is reached, and the battery can have weak cells that can cause costly service interruptions.

Capacity testing

A reliable way of measuring battery capacity is to conduct a discharge test, which can be done with a series of test instruments that enable sites to perform discharge tests at constant current, constant power or constant resistance – as the Megger Torkel range does. Users can even test the batteries online and get extra load units if they need a higher load current.

The company’s BVM, a battery voltage measurement device that is used for individual cell voltage measurement of large battery banks, can also be used in conjunction with the Torkel to perform a completely automated battery bank capacity test.

Impedance testing

To complement this, impedance testers are also available. This test helps to identify weak cells before they cause problems. However, taking the battery off-line for testing is time-consuming and risky – the solution is to use Megger’s battery test equipment, which can be used online.

For example, the BITE line of battery testers will perform online testing that will determine the health of lead-acid batteries up to 7,000Ah. The BITE range of battery testers measures cell impedance, cell float voltage and intercell connection resistance, as well as ripple and float current.

Key testing practicalities

When using a discharge tester, users remove most of the energy from the battery system. However, in the event that the battery is called upon towards the end of the discharge, the user must ensure the operation is not left vulnerable. Impedance tests are very quick and give a good level of confidence that the battery is going to be secure; but an extra measure is to correlate this with discharge tests – at intervals – so that a decision can be made on when to swap out the entire battery.

Some sites may have their own builtin diagnostics and reporting systems. However, in general, it is recommended that batteries are tested at: delivery, to get a baseline value; when they have reached a quarter of their life; half way through; and then at 75% of their life. After this, more regular testing is conducted to verify that the battery will be in good condition towards the end of its life. Even a single cell failure may mean that the battery cannot deliver its power anymore.

Ultimately, regular capacity and impedance testing is essential for predictive maintenance and protection of assets, and it must not be time-consuming or expensive. Megger supplies a range of easy-to-use testers designed to provide either a full test or quick check of the battery’s condition. ESI

This article first appeared in ESI Africa Edition 4, 2018. You can read the full digital magazine here or subscribe here to receive a print copy.

About the company Megger is a global leader with over 100 years’ experience in the design and manufacture of electrical test solutions, providing a comprehensive range of product services for the power stations, electricity supply companies, manufacturing industries and contractors worldwide. |