Fridge

[scoty]

My fridge runs off the boat battery12volts,maintained in harbour by mains charger, as the mains electric does fail frequently, I would like the fridge to run directly from the mains, while in harbour.(to save flat batteries) and food is cheaper to replace.
Anyone know what I need to make this possible
Thanks in advance

 

[Fr J Hackett]

A simple transformer have a look at Maplin 240 volt AC to 12 /14 volt DC

 

[duncan99210]

Most fridges use about 4-5 amps at 12v, so a 120 watt 12v power supply would be OK to run one and cope with the additonal load on start up. Hard wire into the mains, wire the 12v output to the fridge and turn off the fridge at the boat panel. When the mains power is on, the fridge will run: mains off, fridge off. When disconnected from shore power, simply switch the fridge on again ta the boat panel.

Something like this power supply from Maplin is what you need http://www.maplin.co.uk/p/power-pax-120w-switched-mode-dc-fixed-voltage-12v-power-supply-n96ju . Note that as the fridge is 12v dc a transformer without a rectifier will not work.

Oh, and I know you weren't getting much sense from you post on the Liveaboard forum after the spelling mistake in the thread title but you'd have done well to put a reply up pointing out what you were really asking rather than editing your original post: I almost missed what you were asking until I re-read your post after seeing this one.

 

[prv]

How about one of those "battery saver" relays that disconnects the load when the battery voltage drops below a certain level?

Pete

 

[miyagimoon]

Forget, fancy transformers etc. Just do as prv say's. Install a voltage monitor. If the voltage of the batteries drops below a set point (say 12v) drop out the fridge. That way the batteries stay at a reasonable level and the contents of the fridge rot. If the power comes back on the battery voltage will increase and the relay (set to turn back on at say 12.5v) will turn the fridge back on and all is well. Except of course you could now be cooling rotten food!
The other way is to empty and turn off the fridge before leaving the boat. That way the batteries will remain healthy and no food goes to waste.

 

[PaulRainbow]

My fridge runs off the boat battery12volts,maintained in harbour by mains charger, as the mains electric does fail frequently, I would like the fridge to run directly from the mains, while in harbour.(to save flat batteries) and food is cheaper to replace.
Anyone know what I need to make this possible
Thanks in advance

Two question :

What is failing ?

Why are you leaving the fridge on, are you away from the boat or what ?

 

[Caer Urfa]

My fridge runs off the boat battery12volts,maintained in harbour by mains charger, as the mains electric does fail frequently, I would like the fridge to run directly from the mains, while in harbour.(to save flat batteries) and food is cheaper to replace.
Anyone know what I need to make this possible
Thanks in advance

Not sure if I have what you want but I have a Waeco CR40 fridge and use one of their controllers https://cooltechleisure.co.uk/shop/shopwaeco-coolpower-mps-35-mains-adaptor/

Does what it says on the can and has done for years and simple to install.

It automatically switches from 12v when boat is underway to mains voltage when plugged into the marina shore supply or switches back if the mains is disconnected or is shut off.

 

[pvb]

My fridge runs off the boat battery12volts,maintained in harbour by mains charger, as the mains electric does fail frequently, I would like the fridge to run directly from the mains, while in harbour.(to save flat batteries)

I've read this several times, and still can't understand what you're trying to do!

 

[Deleted member 36384]

I've read this several times, and still can't understand what you're trying to do!

As you know, I am fluent in gobbledygook.

Translation: The battery charger stops working frequently because the shore power fails frequently. His fridge runs off the 12V batteries and because of the frequent shore power failures, the batteries are getting flat too often due to the fridge load. He is proposing that he would like the fridge to run of the 240V as a solution to flat batteries.

 

[pvb]

As you know, I am I am fluent in gobbledygook.

Translation: The battery charger stops working frequently because the shore power fails frequently. His fridge runs off the 12V batteries and because of the frequent shore power failures, the batteries are getting flat too often due to the fridge load. He is proposing that he would like the fridge to run of the 240V as a solution to flat batteries.

Ah, thank you. Why doesn't he just get a battery charger which automatically restarts when the power comes on (as indeed most of them do)?

 

[RichardS]

Ah, thank you. Why doesn't he just get a battery charger which automatically restarts when the power comes on (as indeed most of them do)?

I was equally puzzled until the translation was provided ....... I think he is saying that when the shore power cuts out the fridge starts to run on the batteries, of course, and if the shore power is out for a long time the batteries are flat.

The battery saver relay thingy mentioned by Pete is the way forward. I've never seen one "in the flesh" but my boat was fitted with one from the manufacturer so that when the voltage on the house batteries drops to about 11.5V the supply is shut off to all loads and a buzzer sounds.

Richard

 

[pvb]

I was equally puzzled until the translation was provided ....... I think he is saying that when the shore power cuts out the fridge starts to run on the batteries, of course, and if the shore power is out for a long time the batteries are flat.

If that's what the OP meant, then his suggestion of wiring the fridge directly to the mains wouldn't solve anything.

 

[duncan99210]

What I took the OP to be speaking was a way to run his fridge directly from the mains, hence the suggestion about a 12v power supply. However, as others have pointed out, if the mains supply is dropping out and not being reinstated then running the fridge from the mains supply will not solve anything. Best bet is to turn the thing off when not on the boat and leave it open. Take any perishables home in a cool box and bring them back when next visiting the boat.

 

[RichardS]

If that's what the OP meant, then his suggestion of wiring the fridge directly to the mains wouldn't solve anything.

But surely it would since if the fridge is only ever connected to the mains when the boat is unattended, then an outage can never flatten the battery.

Richard

 

[pvb]

But surely it would since if the fridge is only ever connected to the mains when the boat is unattended, then it can never flatten the battery.

If the mains is routinely off for long periods, it wouldn't function as a fridge anyway. And most fridges switch off at 10-11v, so the batteries aren't going to be completely flat, and will recharge when the charger comes back on.

 

[duncan99210]

But surely it would since if the fridge is only ever connected to the mains when the boat is unattended, then an outage can never flatten the battery.

Richard

You're correct but the OPs question was trying to seek a way to make sure the fridge would remain running from the mains. He wanted to preserve his perishable foods without flattening the batteries because of a shore power outage. Given that this seems to be a frequent and prolonged occurrence, he is actually stuck with the only viable option being to turn the fridge off and take his perishables home with him.

 

[RichardS]

You're correct but the OPs question was trying to seek a way to make sure the fridge would remain running from the mains. He wanted to preserve his perishable foods without flattening the batteries because of a shore power outage. Given that this seems to be a frequent and prolonged occurrence, he is actually stuck with the only viable option being to turn the fridge off and take his perishables home with him.

Now you've lost me as well as PVB. Unless the OP has a perpetual motion machine to hand, how can he run a mains fridge from the mains when there's no mains?

Richard

 

[pvb]

Now you've lost me as well as PVB. Unless the OP has a perpetual motion machine to hand, how can he run a mains fridge from the mains when there's no mains?

Perhaps he could introduce a dodgy connection so the batteries give more current...

 

[RichardS]

Perhaps he could introduce a dodgy connection so the batteries give more current...

LOL .... there's seems to be something dodgy going on all round today.

Richard

 

[nigelmercier]

Not sure if I have what you want but I have a Waeco CR40 fridge and use one of their controllers https://cooltechleisure.co.uk/shop/shopwaeco-coolpower-mps-35-mains-adaptor/...

This is the only solution, at least without change-over relays.