The Australian warship holding the only black box detector in the search for Malaysia Airlines (MAS) Flight MH370 is to set sail this afternoon.

ADV (Australian Defence Vessel) Ocean Shield will then be in race against time to track down the vital flight data recorder as the transmitter battery on the blackbox has a limited lifespan.

While it was has a certified lifespan of 30 days, which means it runs out on April 7, search experts say it would usually last another 15 days.

With an estimated 24 days gone, time is ticking for the search — without the battery, the blackbox would no longer be emitting a pulse from the blackbox, making the already difficult task of locating it even harder.

Malaysia has previously said that it is still possible to find a blackbox even if its battery life runs out, though it becomes much harder.

The Ocean Shield has been equipped with a Towed Pinger Locator (TPL-25) and a Bluefin-21 Autonomous Underwater Vehicle (AUV), provided by the US Navy.

The TPL-25 is the blackbox detector that has a reach of about 2km, and moves at a snail-like 5 kilometer per hour. This allows it to only cover less than 150 square kilometres a day.

The AUV is an unmanned underwater vehicle controlled remotely and is equipped with cameras and video equipment, Bluefin-21 uses active sonar to locate underwater wreckage.

The ship is expected to take about three days to reach the search area about 1,850 kilometers (1,150 miles) to the west of Australia.

The search area remains huge, 319,000 square kilometre, and an area roughly the size of Poland.

With only six days till the 30 day period is reached, this leaves about two days of search before the battery officially runs out.

However, the real problem is to refine the search area further as locating equipment will need time as it searches at a speed of only two nautical miles an hour, and it can scan for a signal at a range of one mile.

"We need to reduce the search area in order for the equipment to be deployed effectiely. We don't have a defined area yet," said Captain Mark Matthews of the US Navy yesterday.

Matthews, who was involved in the two-year search to find the black box of Air France Flight 447 after it crashed in the Atlantic Ocean, said that even if debris of the plane is found, also painted a pessimistic assessment of the blackbox search, saying that the blackbox was simply "untenable" as things stand at the moment.

Acting Transport Minister Datuk Seri Hishammuddin Hussein has vowed to not stop the search, even if the blackbox batteries run out, although a different set of equipments would be needed for a search if that happens.

MH370 vanished on March 8, with 239 people on board.