I currently have 4 domestic batteries, each 90Ah. I've had them for years and I've never had any problem with electrics, even though we often use the electrics without a lot of cruising - I hate running the engine just to charge the batteries. Now, however, the batteries are getting to the end of their lives and I need to replace them. They are a funny size (or rather the space they are in is a funny size), and it seems that I can more easily get either 75Ah or 100Ah batteries to fit rather than the 90Ah.
I've done the calculation and the 75Ah set would give me enough capacity, although the 100Ah would obviously give me more for those times I might need it. But a 75Ah bank would get to full charge more quickly and therefore be operating more efficiently, last longer etc.
So up to 100Ah or down to 75Ah? Any views?
Roy