Refrigeration on 12v? Beneteau 331

[HelixOne]

Almost an new owner of a 2002 Beneteau 331. Should be done next week with the purchase.

The boat has a built in refrgerator (Alder Barbour??) and I was wondering which might be a dumb question, but is it possible to run off 12v batteries or is the power drain just too much?

We are on a mooring and do not have shore power.

Thanks,
Craig

[camaraderie]

Adler Barbours are designed to run off 12V...they typically use 5-6 amps when running but once the box is cooled, they only run about 1/2 the time in temperate climates. So YES you can run them off of batteries. I would figure 100 amp/hours the first day of use since you have to cool down the fridge and then about 60 amp/hours for each additional day.
The next thing to worry about is DO I HAVE A BIG ENOUGH battery bank?
Aside from your starting battery you will need about 300 A/h's of batteries to run the fridge for a weekend since you should only use 1/2 available amps before you recharge your batteries. This is equal to about 3 group 31 batteries or 2 4D types.
Then...you need to figure how you are going to charge those batteries since you will need to replace 160 amp/hours every 2 days. You'll need a marine battery charger and a generator (like a Honda) OR some combination of solar/wind generation to achieve this OR you will need a decent sized (80 amp or so) alternator on your diesel and a smart 3 stage regulator...not recommended due to the engine wear running at Idle causes...but still used by many.
Hope that helps...as you can see...it is a bit more complicated than just hooking up a battery...but the ice cubes are worth it!!

[HelixOne]

Thanks for the reply. I am afraid unless I switch to a slip ice will remain in my future. I did always want to get the little Honda generator so that might be a solution.

Regards,
Craig

[eragbag]

I use two 6v deep cycle golf cart batteries in series as my house battery. it gives me about 260 amps which powers my OC 381 at anchor for about 18 hours or so after which a half hour run on the engine tops them off for another 12 hours or so.

[k1vsk]

eragbag
You might want to clarify as this implies you have something other than the stock alternator capable of replacing 50+ amps in 30 minutes.

[eragbag]

The alternator is the standard which came with the boat. The fridge will usually run for about 18hrs or so before the low voltage cutoff turns it off. An engine run of 30+/- minutes usually gets it running for another 12 hours or so. Frankly, I don't understand the mechanics of it all.

[k1vsk]

in 18 hours, one should use approx 5 amps/hr (for the refrig) with a 50% duty cycle or a total of 45-50 amps. Out of a 200amp bank, thats obviously 25% of capacity which should not reduce the voltage enough to cause the shut-off to activate. You either have bad batteries or a bad connection someplace.
Regardless, the stock alternator will only produce 15-25 amps+/- IF THAT in a half hour period; certainly insufficient to recharge the batteries to any degree resulting in constant under-charge (presuming you do this often) and causing the batteries a premature death.