Thank you Ike and GordMay for responding.
Should have mentioned the Brand of battery which is "Full River", Chinese made using AGM
We use two FullRiver -12Vx200AH/20HR on our Catmaran.
Our newly installed Sterling UK "Pro-Charge D" 12Vx40amp has settled and is doing it's job in keeping the correct voltage (13V) in float mode for this Hot Malaysian climate therfore I have satisfied my origional question.
Thanks very much for your assistance.