General power arrangements - slightly disappointing

[PaulRainbow]

A small 200 - 300W inverter may well be useful for charging laptops etc and your wife could use low power straighteners but any inverter powerful enough for a conventional mains hairdryer is not going to be realistic. You can get 12V hairdryers but I understand that they give out so little heat that your marriage is more likely to end up on the rocks than the boat.

Richard

DC-DC converters work well for charging laptops Richard. I use them to run my laptop, power the TV and the soundbar and to charge phones and tablets via high output USB sockets.

 

[RichardS]

DC-DC converters work well for charging laptops Richard. I use them to run my laptop, power the TV and the soundbar and to charge phones and tablets via high output USB sockets.

Not with two of our laptops unfortunately .... they have a 3rd wire to detect non-OEM chargers.

As we need the inverter on-board for the staighteners we tend to use it for everything which is not USB.

Richard

 

[PetiteFleur]

I didn't appreciate that a smart charger is not affected by additional load whilst charging, in which case there is no need to isolate the batteries from the 12v system when charging.

Not sure about an inverter with such a small battery bank.....not with my wife's hairdryer in her holdall!!

So I have 2 x 110ah batteries.....what charger would you (anyone) recommend. I can't see a situation where I want to operate the windlass on shore power but definitely the fridge...most other things are small fry.

I also have 2 x 110ah batteries, a 1 2 off both switch and a 5a Cetek charger which I use when in a marina on the battery currently being used. I've a fridge etc, and the camper type rcd/13a sockets. Works for me - I like the KISS principle.

 

[[70521]]

a boat I bought yesterday and am delighted with has for its main electric cut offs, two ancient bakelite switches, and the bilge pump switches off an old domestic light switch. It's all so charming I might just leave it in.

Delighted you got back safe and sound.

 

[SlowlyButSurely]

Why, what's wrong with asking here ?

It's what the forum is for, it isn't a redirect service.

Hi Paul,

He did ask here and what he asked for was "only a brief overview of components required" which is exactly what Tony Brooks website has with simple circuit diagrams etc.

The 12voltplanet website also has a very good Knowledge Centre and will enable the OP to price up the various options and work out whether he wants to upgrade or stick with the simple and reliable 1-2-Both system he already has.

Just trying to help!

 

[macd]

Currently two batteries in a bank with a 1 2 BOTH switch.

??

If you're saying you have a total of two batteries and that they're wired as a single bank, then the switch is largely redundant. Or perhaps you mean two batteries, one starter, one domestic, wired through the 1-2-both? That would be the more usual arrangement. It would be helpful if you could remove the ambiguity.

 

[solent clown]

Delighted you got back safe and sound.

we didnt sail it chap, took your advice, but we did visit it

 

[CLB]

I didn't appreciate that a smart charger is not affected by additional load whilst charging, in which case there is no need to isolate the batteries from the 12v system when charging.

Not sure about an inverter with such a small battery bank.....not with my wife's hairdryer in her holdall!!

So I have 2 x 110ah batteries.....what charger would you (anyone) recommend. I can't see a situation where I want to operate the windlass on shore power but definitely the fridge...most other things are small fry.

Most boat fridges are duel powered. It's usually the only thing that is. It should run on 12v when off shore power, and 240v when plugged in.

 

[pvb]

Most boat fridges are duel powered.

That's news to me, most fridges I've seen just run off 12v. If the charger is on, the 12v will come from that.

 

[macd]

That's news to me.

And me.

 

[prv]

Most boat fridges are duel powered. It's usually the only thing that is. It should run on 12v when off shore power, and 240v when plugged in.

I've never seen one that does that.

Not to say dual-voltage compressor fridges don't exist, but the only dual 12v / 240v fridges I've encountered were caravan models designed with the option to also run on gas (even if this wasn't necessarily used). These use the absorption cycle instead of a compressor, which means no moving parts and the ability to run on any source of heat, like LPG or paraffin. However, running on heat instead of compression means they use far more power when run electrically - not a problem when you're plugged into the caravan site hookup, or towing behind a running car, but not good for sailing boats (or indeed motorboats that ever stop anywhere but a marina). The absorption cycle also demands that the system be kept perfectly upright to allow the liquid chemicals to flow properly through the complex tubing - caravan fridges often have a little bubble-level nearby to help you set the van up level.

I've heard of absorption fridges run on gas on catamarans (no heeling) in the past, but most people don't want to do that now for gas-safety reasons. So this type of fridge is firmly landbound nowadays and boat fridges will almost always be compressor type.

Pete

 

[VicS]

That's news to me, most fridges I've seen just run off 12v. If the charger is on, the 12v will come from that.

Although you can get mains adapter units which feature mains priority when permanently connected, automatically switching to mains when it's detected and back to low voltage when mains is lost or disconnected.

 

[CLB]

That's news to me, most fridges I've seen just run off 12v. If the charger is on, the 12v will come from that.

And me.

I've never seen one that does that.

Really. My Engel fridge fitted as original equipment to my 1997 boat can't be that unusual in having both a 12v and 240v supply going to it. Standard fit in Sealines of the age. Maybe this is a MOBO/Saily thing.

Having looked on the Dometic website, it seems that most models are available in either a 12v only version or a dual voltage version. Coudl it be that Mobo builders tend to go for the latter, while yacht builders the former?

I have owned a few Mobos, all with factory fitted fridges and without exception, every one was dual voltage. From memory they all worked on a 240v bias. ie if you left the 12v and 240v fridge breakers on, it would run on mains if available, and 12v if not.

 

[pvb]

Although you can get mains adapter units which feature mains priority when permanently connected, automatically switching to mains when it's detected and back to low voltage when mains is lost or disconnected.

As most decent battery chargers now also work as a power supply, the added complication of mains adapters isn't really necessary.

 

[prv]

Having looked on the Dometic website, it seems that most models are available in either a 12v only version or a dual voltage version. Coudl it be that Mobo builders tend to go for the latter, while yacht builders the former?

Thanks - you're probably right that it's a mobo / raggy thing. I don't know much about the habits of small-to-medium mobos (though I like reading about the systems geekery of American-style trawler yachts, who frequently install US-kitchen-sized 120v fridge-freezers ).

I understand that boat type fridges generally run the compressor itself on high-voltage three-phase from a tiny inverter mounted right next to it, so it's quite plausible that the inverter might be designed to accept both 12v DC and 240v single-phase.

Learn something new every day :encouragement:

Pete

 

[vas]

not sure how helpfull I can be on that dual fridge thing,

my mobo fridge (Frigoboat) had a black box (well ss...) that would take two inputs (24V and 220V) and ONE output to the fridge (which is 12-24V)
it was a 220V priority circuit all right, but imho quite pointless as you end up having various inverters, converters et al working together producing more heat (in losses)
So disconnected it and still all works fine

keep in mind that the dunfoss controller installed in most fridges (expensive piece of kit!) is typically 12-24V

cheers

V.

PS. odd thread indeed

 

[Sea-Fever]

No need whatsoever.



An inverter would be a bad idea for your setup.



I'd suggest a Victron charger, with outputs for both banks. This will keep all batteries charged and will act as a power pack to run stuff when on shore power. You might get by with a 20a charger, but for the small difference i'd go for 30a, for example https://www.batterymegastore.co.uk/...rgy-chargers/victron-energy-bpc123044002.html

Shore power needs an RCD and MCBs for each circuit. If the AC ground is bonded to the DC -ve you need to fit a galvanic isolator.

You don't have enough batteries. 2x110ah leisure batteries would be the bare minimum for a 33ft boat, plus an engine battery, which can just be a suitably sized car battery.

The 1-2-B switch isn't a good solution for a modern cruiser, you would be better off with a starter battery, on its own switch and at least a pair of domestic batteries, also connected to their own switch. A 3rd switch gives emergency engine starting from the domestic bank, amongst other things. You will need to add some split charging then, if you don't already have it.

This is helpful, thanks....I just needed an idea of the general 'topology' (if that's the right word) of the power system on small boats, although obviously there are many variants.

To clarify, I have two 110ah in a battery compartment both wired to a 1-2-B switch. I.e. they can independently or jointly power the single 12v system. I am unsure at this stage where the alternator is connected but I suppose it goes to the switch to charge whichever battery is providing the supply at the material time. I can check this when I next pop down to the boat.

 

[Sea-Fever]

??

If you're saying you have a total of two batteries and that they're wired as a single bank, then the switch is largely redundant. Or perhaps you mean two batteries, one starter, one domestic, wired through the 1-2-both? That would be the more usual arrangement. It would be helpful if you could remove the ambiguity.

As above, they either independently or jointly (in parallel) power the 12v system.......

At least i think they do.
....starting to doubt myself now.....

(Rips out all the wire from boat and starts again)

 

[Momac]

I have owned a few Mobos, all with factory fitted fridges and without exception, every one was dual voltage. From memory they all worked on a 240v bias. ie if you left the 12v and 240v fridge breakers on, it would run on mains if available, and 12v if not.

This also seems to me quite normal.

 

[PaulRainbow]

This is helpful, thanks....I just needed an idea of the general 'topology' (if that's the right word) of the power system on small boats, although obviously there are many variants.

To clarify, I have two 110ah in a battery compartment both wired to a 1-2-B switch. I.e. they can independently or jointly power the single 12v system. I am unsure at this stage where the alternator is connected but I suppose it goes to the switch to charge whichever battery is providing the supply at the material time. I can check this when I next pop down to the boat.

That is the usual way it works.

You are also correct as to how the switch works, 1 selects one battery, 2 selects the other, both is erm...both.