Auto switching from 12v to 240v

[Québec]

We're away from our boat all week, sometimes longer. Recently changed the 3x leisure battery bank. It was suggested (not recommended) that if we wanted to keep the 12v fridge on while we're away and the boat is plugged into the shoreline 240v mains, rather than having it constantly running off the 12v system and using the Sterling charger, we could install an auto voltage selector such as this:

 

http://e.dominohosting.biz/dca/mpsdb01.nsf/PDF2/MPS-50.pdf/$file/MPS-50.pdf

 

It means we could run it off the mains but as soon as the main is switched off - either manually or if there's a fault, the fridge automatically reverts back to the 12v system.

 

They cost a lot c. £70... But cost aside (!) is it worth considering? Has anyone got one, used one?

[boots]

If I'm understanding correctly, not sure what you would gain? By connecting it to the 12v supply of the fridge would you not then also be connecting it to your batteries and so it would be trying to act as a battery charger? What's the problem with running as you are now?

 

I assume you leave the charger on while you are away?

[Arthur Brown]

Our host had these http://www.canalworld.net/forums/index.php?showtopic=56174 for sale either would do the job well.

 

Why would you want your fridge on for three weeks unattended? The risk of the fridge going off for a week then coming on again and thence holding a chilled bio-hazard is too great for me

 

Milk -dried

meat -not three unattended weeks

fish -------""-------

[Paul C]

Don't know much about the device (ie can't recommend it or not, as such) but it does sound like its a bit limited for £70. You could get a reasonable battery charger for that, and it would be able to convert 240V to 12V not only for the fridge, but for everything else too. Including making sure the batteries are fully charged and kept in good health.

 

Or are you saying you already have a Sterling charger, but are simply choosing not to use it? That doesn't make sense to me.

[jenlyn]

We're away from our boat all week, sometimes longer. Recently changed the 3x leisure battery bank. It was suggested (not recommended) that if we wanted to keep the 12v fridge on while we're away and the boat is plugged into the shoreline 240v mains, rather than having it constantly running off the 12v system and using the Sterling charger, we could install an auto voltage selector such as this:

http://e.dominohosting.biz/dca/mpsdb01.nsf/PDF2/MPS-50.pdf/$file/MPS-50.pdf

It means we could run it off the mains but as soon as the main is switched off - either manually or if there's a fault, the fridge automatically reverts back to the 12v system.

They cost a lot c. £70... But cost aside (!) is it worth considering? Has anyone got one, used one?

I had one for my waeco fridge, it was good kit, but the fridge was crap.

[The Bagdad Boatman (waits)]

If the system goes live only when the mains trip out, will it switch off as soon as the mains come back? 12v fridges are very greedy of power which is why gas fridges are so popular. The electrolux 12/250v gas uses a heater coil to replicate a gas flame.

[ditchcrawler]

We're away from our boat all week, sometimes longer. Recently changed the 3x leisure battery bank. It was suggested (not recommended) that if we wanted to keep the 12v fridge on while we're away and the boat is plugged into the shoreline 240v mains, rather than having it constantly running off the 12v system and using the Sterling charger, we could install an auto voltage selector such as this:

 

http://e.dominohosting.biz/dca/mpsdb01.nsf/PDF2/MPS-50.pdf/$file/MPS-50.pdf

 

It means we could run it off the mains but as soon as the main is switched off - either manually or if there's a fault, the fridge automatically reverts back to the 12v system.

 

They cost a lot c. £70... But cost aside (!) is it worth considering? Has anyone got one, used one?

Surly the danger her is if the mains fails you fridge will run from your batteries until the supply is restored. If the failure is due to a fuse, trip, some one unplugging the boat the batteries could well be dead before you returned to the boat

[Québec]

Thanks for the replies

 

 

Paulk C - Or are you saying you already have a Sterling charger, but are simply choosing not to use it? That doesn't make sense to me.

 

Yes we have a Sterling charger, and it didn't make sense to me either at first. But the discussion was about minimising wear and tear on the batteries by having the fridge on all the time i.e. contant drain and constant charging (I know that's not how it works in reality but the fridge IS on all the time). That led on to thinking about whether it's possible to run the fridge off the mains (yes) but also being able to switch easily back to 12v when we're actually on the boat and out on the cut.

 

 

Ditchcrawler - Surely the danger here is if the mains fails you fridge will run from your batteries until the supply is restored. If the failure is due to a fuse, trip, some one unplugging the boat the batteries could well be dead before you returned to the boat

 

Yes, of course. That's what happens (and has happened) anway. The point is not the non-existent fail-safe, but to able to switch easily from 12v to 240v and back again.

 

[Woodstock]

we've got one of these (it came with the boat) and it works well- If we're in the marina it runs off the shoreline, if we're travelling then it switches to 12v. We only use the boat at weekends though, so switch the fridge off when we're not on it

[smileypete]

We're away from our boat all week, sometimes longer. Recently changed the 3x leisure battery bank. It was suggested (not recommended) that if we wanted to keep the 12v fridge on while we're away and the boat is plugged into the shoreline 240v mains, rather than having it constantly running off the 12v system and using the Sterling charger, we could install an auto voltage selector such as this:

 

http://e.dominohosting.biz/dca/mpsdb01.nsf/PDF2/MPS-50.pdf/$file/MPS-50.pdf

 

It means we could run it off the mains but as soon as the main is switched off - either manually or if there's a fault, the fridge automatically reverts back to the 12v system.

 

They cost a lot c. £70... But cost aside (!) is it worth considering? Has anyone got one, used one?

What's the output of the Sterling Charger?

 

The real risk may be that a cell shorts while you're away, and the charger kicks into high gear and all the batts overheat.

 

In which case a charger with a smaller output could be better, say just enough to cover fridge and bilge pump. When a so-called 'smart' charger is on float, it may supply enough enough current to run the fridge without needing to go into a charge cycle.

 

If worried about the flat batt thing, maybe just have a relay to connect the fridge while mains is present, plus an over ride switch and a warning lamp or two. A min max thermometer will tell if the fridge has been off while you're away.

 

cheers, Pete.

~smpt~

[jonathanA]

Thanks for the replies

 

 

 

Yes we have a Sterling charger, and it didn't make sense to me either at first. But the discussion was about minimising wear and tear on the batteries by having the fridge on all the time i.e. contant drain and constant charging (I know that's not how it works in reality but the fridge IS on all the time). That led on to thinking about whether it's possible to run the fridge off the mains (yes) but also being able to switch easily back to 12v when we're actually on the boat and out on the cut.

 

 

 

Yes, of course. That's what happens (and has happened) anway. The point is not the non-existent fail-safe, but to able to switch easily from 12v to 240v and back again.

 

 

 

wouldn't it be good to have the fridge conencted to the batteries so that the sterling charger would go into float but occasionally the draw of the fridge would kick it into charge mode, assuming the sterling couldn't meet the demand of the fridge which unless its the 10A version I can't think it wouldn't be able to..

 

so the issue then becomes what happens if the mains fails..and as SMPT says you could fairly easily arrange a mains operated relay to say overide the fridge circuit breaker on your 12V distribution panel. a neat trick would be to make it a self latching relay that needs a push button (momentry type) to switch it on, but if the mains failed the fridge would be disconnected until you pressed the button again, so you'd know the mains had failed at some point.

 

Guess coming back to a fridge with ruined stuff in might be preferable to not knowing ithe fridge had been off for a while, but depends on why you need to leave it on i suppose.