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Swapping plugs pain


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The frig runs on either 230 thru transformer, or 12 from cigar lighter. Swapping over the plug at back of frig is a pain. Must be a switch instead I can set up, back cant picture what? Any ideas?

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The fridge has two plugs? a 230v one and a 12v one?

Can't you just leave them both plugged in, the fridge will likely prefer the 230v one over the 12v input.

 

Which make/model fridge is it?

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You can use a changeover relay. Wire it so the 12v feed from the transformer does 2 things - 1 turns the relay on, and 2, feeds the fridge through the now closed relay contacts. When that feed is disconnected - ie. no shore power, the relay turns off, and falls back to the other relay contact with the 12v battery power. You don’t need to do a thing that way.

 

May sound complex, but it’s about the easiest job you could ask a competent marine electrician to do.

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If you want to continue to use both AC and DC, I would get a DC socket fitted to the 230V Tx unit. It may require an extra box the socket fits into. Then plug the 12V plug directly into the socket. Then the fridge always has the ciggy plug available and all you do is fit it directly into the 12V DC or into the 230V adaptor.
I would take the 230V tx to an electrical service shop and get them to do it so as it is done safely and competently. They should be able to supply the DC socket.

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Hard wire the fridge to 12v.  Protect the circuit with a breaker or fuse.   Then get a charger for when you are at dock to keep the battery charged.

 

And now for my sales pitch.  :thumbup:  

 

I have a very high quality and very very high output Victron Centaur 12v 80amp marine charger that I am about to sell if you are interested.  Send me a message if you like,  I will post this on the classifieds shortly and then trade me. 

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If he uses a relay, he can run the relay output to his existing aux. socket, and leave the fridge plugged into that all the time. This is the cheapest and best option. Only parts needed are a >$10 relay and a few crimps, you end up with an automatic system. 12v fridge suppliers such as Fridgetech sell this system as an option with their fridges.

 

The charger route does work, but with some potential draw backs. First if shore power fails, the fridge flattens your batteries before it stops working. Second, if the charger isn’t big enough, the fridge load may keep it from staying in float charge, which will stuff the batteries. MCP’s charger is certainly big enough to prevent this.

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Simple answer lateral, the relay. At no stage is the 12v transformer output and the battery 12v feed joined. That’s what the changeover relay is for - it selects one feed or the other, and outputs that power only to the aux. socket Vic plugs his fridge in to. Wired up to prefer the transformers output when available.

 

What MCP suggests would work, as you as, as long as the changer is smart, and of sufficient size that the fridge cutting in does not kick it back into bulk / absorption stage, as that will damage the battery over time. The other issue, as I said earlier, is if shore power fails, the fridge is running off the battery, which will run down until very flat before the fridge cuts out. If you do the relay option, you can choose what side of the battery switch to wire the fridge feed to, if after the switch, the fridge won’t discharge the battery while the switch is off, if shore power fails.

 

If you own a transformer that can run your fridge, it’s a better system.

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Other than that it will have a recommendation of max battery capacity of about 150ah, assuming it has the correct charge rates for your batteries, nothing at all. The bigger one will charge faster, but in most cases that’s not very important.

 

Unless you want to run the fridge off the batteries while the boats at the dock, keeping the batteries full with the charger. Good chance that will stuff the batteries and the charger, after some time. But you have a power supply running the fridge, so no problem.

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