Microtek Inverter not fully charging the batteries

I have a 6 months old Microtek 3KVA Inverter which is connected in series to 4 Brand New Exide IN 1500 Plus 150Ah rating Inverter Batteries (48 Volts system). Though the inverter charging LED indicates that the batteries are fully charged (battery charging indicator light stops flickering) none of the indicators in the four batteries show the typical green glow in the visual charge indicator. Upon connecting an ammeter in series to check for the charge current the ammeter registered only 2-3 amps initially and later dropped down to 0 Amps. What I understand from this test is that the Inverter circuitry has sensed that the battery does not require any further charging and therfore the charging amperes is zero. If this is an indication to show that the batteries are fully charged, why have the glow indicators in the battery failed to indicate green, typical color of a fully charged Exide IN 1500Plus inverter Battery.