Opinions Wanted on Battery Bank Capacity

[Heathenly Twins]

Was wondering if you could opine on a proper battery bank capacity for me.

The boat is a 26' cruising sloop that i am preparing for long-term open-ended cruising. I want this boat to be capable for offshore and coastal.

I'm definitely going with lithium batteries for the house bank as they are just superior in terms of performance IMO.

I'm putting in a new 25hp auxiliary diesel engine but haven't decided on an alternator yet. Options are 40, 80 or 120ah. I'm inclined to choose the latter.


Right now the boat is in British Columbia which means a lot of motoring so I will probably forego much of a solar installation until I have a better idea of power usage. I might buy a gas powered generator as I don't idle diesels. I mention the location because the region often has weeks of thick cloud cover especially in winter so solar panels can be a bit ineffective and in winter power demand goes way up.

In summer I might hit up a marina as often as once a week but generally will be on the hook.

Loads will include some sort of fridge and ideally a freezer also, Pelagic tiller pilot used most of the time, two tablets used as chart plotters and LED cabin lights. In winter a forced air diesel heater and up to 16 hours a day running at least two mid-level laptops.

Sorry it's kind of vague, I'm having to spec an entire elecrical refit on aboutb50 days of cruising with this boat. It's all new.

Oh and the area on my boat could fit as many as 5 100ah Battle Born batteries but 4 would be a lot easier.