47 foot boat
400AHrs. We use as much as we can generate from solar. Lots in summer 120AHrs, not much in winter 50-80 AHRs
Battery bank size needs quite a few parameters to calculate optimally.
The most important factor is how you are going to recharge the batteries.
Batteries do not produce power they only only store it. Every AHr you use must be replaced (plus a bit more)
The method of charging and how you intend to use the boat makes a big difference to battery size. A boat re-charging from the engine battery, or generator
for example will need a larger battery bank than a boat relying on solar. A boat with your requirements and equipment
could get away with quite a small battery bank if you you only want to spend a couple of days away from the marina, but extend this to 5 Days and the results will be different.
First consider how you will replace the power you use. Your optimal battery bank size will flow on from this.
Many people fit very large battery banks because they claim, quite correctly, that increases battery life, but it should be remembered that the minimum battery bank cost per year is achieved with a bank where the average discharge is somewhere around 50%.
Fitting a very large bank that is rarely taken below a 85% SOC gives people a warm fuzzy feeling
, but battery costs per year rise sharply over a smaller bank and while exchanging batteries less often is a nice compensation the fact that more need changing (and they are bloody heavy) offsets this somewhat.
You also need to consider the relative costs of a larger battery bank verses spending the additional money
on energy saving devices, or on increasing your production.
It is difficult to predict power usage from just a list of equipment
, but it you want to stay away from shore power
for a reasonable length of time you are likely to be running the engine 1-2 hrs a day (in addition to the solar contribution) to charge the batteries. A large battery bank will only make a small difference to run time. I would be looking at ways to increase production and reduce consumption
as a first priority.