boat fridge - do you keep them on when cruising?

[Momac]

It could depend on what kind of 12v fridge we are talking about.
A 12v compressor fridge is reasonably energy efficient and as examples above will demonstrate, will run for days with a couple of 110Ah batteries. Alternativly a 12v absorption fridge will empty even a substantial bank of boat batteries before tea!
I have an old 3-way, Gas, 12v or 240v fridge. There is no practical way to run the 12v from a battery. It can only be on 12v when the engine is running. The current draw is phenomenal. But to give it it's dues, it was never designed to work any other way. It is a caravan fridge really, so gas on the campsite or 240v if available. 12v when being towed by the car.

That could be where the modern 'myth' comes from.

Even so you still run the fridge on 12 Volts with the engine running. Which the OP says he has been advised he should not do.

 

[Scubadoo]

If the shore power fails it will switch to the leisure batteries.

Our bilge pumps are wired to the starter battery not the leisure batteries that the fridge is wired to.

Our shore power has not failed to date.

Interesting, was that a factory set-up or did you change the bilge pump wiring to the starter battery.

 

[boatone]

Even so you still run the fridge on 12 Volts with the engine running. Which the OP says he has been advised he should not do.

Sorry to be boring but this thread is becoming rather boring

Fridges that run from a 12 volt supply will not suffer harm if they are on when the engine is running - they usually have a voltage tolerance level of around 14 to 10 volts. I cannot recall ever seeing any advice that states that a fridge should not be run when engines are charging the batteries.
How long the fridge will run on battery supply only is simply a factor of total battery capacity - in my experience the vast majority of boats simply don't have enough. 100a/h battery will never supply 100 amp hours under any conditions. It will probably not charge above 85% and running it down below 50% will shorten its life so that makes 35 amp hours of useable capacity available - not enough to run an average small 12v fridge for 24 hours.

Everyones installation is different so there can be no "one reply fits all" answer.

 

[CX54WEK]

Interesting, was that a factory set-up or did you change the bilge pump wiring to the starter battery.

Factory as far as Im aware.

The boat is 11 years old and we have owned it for the last 6.

 

[Elessar]

Factory as far as Im aware.

The boat is 11 years old and we have owned it for the last 6.

are you sure? I would expect them to be wired before the battery isolation switch so they will stay on with the batteries off - is that causing a false assumption?

 

[Alpha22]

When I had a compressor fridge, it was a dual voltage 12/24v but the spec stated it would be happy with anything up to 30v. I can't see any alternator giving it a problem.

 

[CX54WEK]

are you sure? I would expect them to be wired before the battery isolation switch so they will stay on with the batteries off - is that causing a false assumption?

Nope.

ETA: We dont switch off our isolators and have dry bilges so it has never been a problem

Well I say that, the bilges are usually dry but we currently have a bit of Humber in there as the raw water pump seals have given up the ghost, again!

 

[boatingdave]

I've just read this long thread. Am I the only one that keeps food in the fridge rather than just beer? And for consistency, our fridge is on all the time although, as per an earlier thread, sometimes switched off at night because of the noise (slightly worse on 12v).

 

[CX54WEK]

I've just read this long thread. Am I the only one that keeps food in the fridge rather than just beer? And for consistency, our fridge is on all the time although, as per an earlier thread, sometimes switched off at night because of the noise (slightly worse on 12v).

We have a pack of butter, some milk and room for a pack of bacon in the fridge. Anything else is just taking up valuable beer space

 

[boatingdave]

We have a pack of butter, some milk and room for a pack of bacon in the fridge. Anything else is just taking up valuable beer space

Lol. I asked for that. Hope you like your Nissan Almera btw.

 

[CX54WEK]

Lol. I asked for that. Hope you like your Nissan Almera btw.

Depends how you class like!

Great reliable and economical work horse but a bit slow and boring.

B300 XVH is the not so sensible alternative

 

[boatingdave]

Depends how you class like!

Great reliable and economical work horse but a bit slow and boring.

B300 XVH is the not so sensible alternative

 

[abraxus]

If the shore power fails it will switch to the leisure batteries.

Our bilge pumps are wired to the starter battery not the leisure batteries that the fridge is wired to.

Our shore power has not failed to date.

I have the reverse of that set up, in that I'm on shore power and my bilge pumps are wired directly to the leisure bank (500ah), and I leave my fridge on all the time.

The other difference is that I have the battery switch switched to the starter battery when on shorepower. The reason being that if in the unlikely event that the shorepower fails for an extended period, or my charger fails, then the fridge will run off the starter battery, and so can only drain one battery flat rather than a bank of four. The leisure bank remains intact with the bilge pumps attached.