MAS chief executive officer Ahmad Jauhari Yahya has denied reports that the airline had been lax in servicing the batteries of its pingers.

“We confirm that we have a maintenance programme whereby the batteries are replaced prior to expiry. We do know that the batteries are due for replacement only in June 2014,” he told a press conference today.

The pinger, or more formally known as underwater locator beacons, is a component of an aircraft’s black box that emits a sound once every second until its batteries are depleted, upon submersion in water.

This sound can be detected up to a distance of 1.5 kilometres with specialised underwater microphones to help searchers locate the black box in the event an aircraft crashes into the water.

Earlier, CNN had reported the pinger’s manufacturer Dukane Seacom Inc saying that MAS has not returned its pingers to replace its batteries, and using old batteries would mean that it would have a shorter lifespan than what is legally required.

The company’s president Anish Patel told CNN that the MAS’s pingers were due for battery replacement in 2012, but his company has not received them to date.

“We have no record of those units ever coming back for a battery replacement," Anish was quoted as saying.

The lithium battery strength weakens over time, requiring replacement every five years.

However, he added that apart from a maintenance lapse, there are other possible reasons why his company did not received the pingers.

“Up until 2009, 2010, we used to see it on a regular basis. So, they could have gone to another protocol such as doing it themselves, or they could have gone to another repair facility,” he said.

Shorter life-span for old batteries

The pingers are reportedly sealed and its batteries are not user-replaceable, therefore are typically returned to the manufacturer to be fitted with new ones.

Regulatory requirements mean that pinger batteries must last at least 30 days. To meet this requirement, Anish said fresh batteries could last up to 35 days.

If MH370’s pingers used old batteries, Anish said it could then last only 20 to 25 days, meaning the missing plane's would no longer be emitting signals by now.

The lithium battery’s strength weakens over time, requiring replacement every five years.

Previously, CNN had also quoted unnamed safety auditors that MAS stores its pingers in hot and humid conditions, contrary to manufacturer’s recommendations that it should be kept refrigerated or at room temperature.

This could potentially half the battery's life of MH370’s black box pingers if they were among those improperly handled, the report says.