If the battery was fitted in japan then you need to change it, the vehicles sit around in the auction lots and on board the ship, a battery discharges as there are ECUs and the radio memory that all take power,. once the voltage drops to 10.5volts the cells get damaged and are beyond recovery. You need to check that the alternator is working, with the engine running check the voltage at the battery it should be at least 13.5 volts. P.S. Your pic shows the battery has at some time been upgraded to a 60Ah as the original factory fitted one was 45Ah. check the voltage with the engine off it should be a minimum of 12.1volts and running 13.5v to 14.5v. the vsr relay is there to charge the leisure battery once the starter battery is fully charged.