I have three 90Ah AGM batteries (giving 270Ah for house use) and one separate 90Ah AGM battery to start the Yanmar 3GM30 (27HP) engine. They are all identical in specs (Absorbed Power AGM GT12-90C), each weighs 29kg and all 9 yrs old. I deliberately chose the start battery to be identical to the house batteries.
The start battery is having trouble maintaining charge so I'll replace all four of them.
I'll still have to buy three smallish batteries for house use because there is no room under the sole for one big one.
Question (1): Any current recommendations on a brand to select ?
Question (2): Is there any reason why I should NOT continue with using a deep cycle start battery rather than a, supposedly, high discharge type start battery? (It's only a small engine remember).