I installed 4 x 145ah Super Cycle AGM's 18 months ago (Still under Warranty). They were marvelous giving us days service before needing charge. Usual discharge to 12 volts.
This week suddenly we have extremely low capacity and using our normal charge methods (Sterling shorepower 40A charger set to AGM) or the boat engine alternator. Absorption charging at 14.6V and 14.4V respectively. The shorepower drops to 13.6V for float.
I only seem to be able to get 50ah storage into batteries (using NASA Marine Clipper BM2 battery monitor) and then the charge current is down to 1 or 2 Amps within 4 hours or so.
Why would this have happened to four new batteries and so suddenly?
Help very much appreciated.