1942-1960
After the British surrender, two Japanese officers, Lt-Col Numaguchi and Major Akiyama, conducted a survey of all of Singapore's fortifications as they were in Febuary 1942. The Pengerang battery was covered and they noted that both the 6" guns on Pengerang had been scrapped.
The British knew the two 6" guns had been destroyed under their own denial scheme, as it had been officially reported and corroborated by a Royal Engineer officer. The destruction of the actual emplacements however were not noted in any reports, and so the British had to assume they were still intact.

From a 1944-45 British report we can get a better idea as to the extent of Japanese operations in the Pengerang area and what was left of the battery.
A small scale aerial survey was conducted by the British that revealed considerable Japanese activity in the area. The Battery Observation Post (BOP) was even seen to still be in place. From this the British assumed that the Pengerang battery had been rearmed and brought back into operation.

Further intelligence reports stated from a "source", that up to April 1945 there was in the area, 30 Japanese troops, 50 mixed troop, 12 police and 300 army coolies.
The report went on to state that there was a oil dump, food stores, officers quarters and 4 batteries of 6 AA guns, and that no civilians were allowed near the area. An independent source adds, there was even a possible Japanese radar station at Kampong Pengerang as well.

The Japanese obviously had big plans for the Pengerang area. This was then confirmed by a later report from the "Interservice Liaison Department" (I.S.L.D), quashing the previous estimated troop strength from 400 up to 1,600, after Japanese landings were observed in December 1944.

Any possible British plans for the re taking of Malaya and Singapore, would have had to have factored in the threat that Japanese held Pengerang would have posed to any invading allied force.

Outside of British military reports there are also civilian accounts of Pengerang under Japanese control. It was reported the Japanese sent local workers to the Pengerang area to presumably work at the already well established pre war bauxite mines. The accounts point to the harsh conditions under the Japanese resulting in many deaths. Incidentally bauxite mining still continues today in Pengerang.

The Pengerang area also seemed to have had some anti Japanese groups based there including a Communist Party headquarters which was later tracked down and set fire to by the Japanese.

Sadly no reports have been found as of yet in documenting the Pengerang battery in the immediate postwar period. But it's pretty evident that the British never brought back on-line the Pengerang coastal defences to what it was in the prewar years.

Pengerang in its post war years also saw much action during the Malayan Emergency. Many British units were stationed in and around Pengerang tasked with hunting down communist terrorists.
Also during the Indonesia-Malaysia confrontation, Pengerang once again saw action with its beaches becoming landing points for Indonesian insurgents. I have found one report of "hunters" in the area engaging one such insurgent group near Tanjong Pengelih.