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Newbie Questions re 12v Power Inverters


gb99190

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We are new narrow boat owners having purchased our first 45ft narrowboat this year. The boat has a few 230\240v sockets and about 6 12v ones as well as 12v lighting.

 

All is well in the marina as everything works fine TV,laptops, tablets, imeersion water heater etc. and of course the cooking is gas. However for our next trip out we wish to travel further afield and the boat does not have an inverter. It seems to be quite expensive to retrofit an inverter?

 

We have a cooler with a 12v and 240v connection but it is a cigarette lighter type and all 12v sockets are 3 pin round ones. I have seen 2pin to cigarette lighter adapters @ 10amps and a 3pin to cigarette lighter @ 2amps but not sure whether these are suitable for the cooler. Also the TV freeview box runs off 240v - so no inverter/no TV - a boon I am sure sometimes!! And we have a small 240v slow cooker. I have seen a portable 12v to 230v inverter with a single socket output using hopefully one of the adapters above.

 

Does anyone have any experience of these types of adapters or is there any advice you could offer?

 

Many thanks

 

John

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Take the cigarette lighter connector off and fit a 3 pin plug? - don't think this is a good idea since cigarette lighters current rating is more than the sockets.

 

Be careful that your boat wiring to the 12V sockets is big enough to take the current for your inverter...

 

The smallest of slow cookers will take 10 amps at 12V + 2/3 amps for inverter efficiency + whatever the TV needs if you plug that in as well.

 

Really it's best to install a real inverter - suggest at least 500 watts.

 

It should not take more than a couple of hours to install an inverter so I don't know why you think it's expensive - unless you have asked a boatyard for a quote!

Edited by Tiggs
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Before you think about an invertor, ask yourself how you are going to generate the electricity all these 240v appliances will use once you area away from a shore mains connections.

 

Unless you have substantial on-board generating capacity and adequate battery capacity, immersion heaters, slow cookers and the like are just not viable.

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Anything involving heat/cold uses lots of juice, and as above, you'll need suitable storage for things like cookers.

 

Is the TV definitely 240, or does it have an adaptor? (Check back of TV for required input voltage)

 

Consider a 12V LED monitor to replace if it is 240V.

 

For now, you could put the cooler near the batteries, and run a (fused) cable if existing wiring is a problem

 

Inverters are cheap and easy enough. Could be integrated with existing 240v system via a fusebox

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Unless you are intending to only use a tiny inverter such as those offered for car cigar lighter sockets powering just one device (say max 120 watts) then it needs to be wired directly to batteries via suitable fuse and maybe isolator. In any case stay well away from from cigar lighter sockets, they are rubbish and in most cases not fit for purpose.

 

If the mains output is going to feed your existing AC disribution system then consideration needs to be given to RCD trips, neutral/earth bond and changeover switch from shore mains power.

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I suppose the first thing to do is look at your cruising pattern, and work out what you absolutely must be able to operate when not on shore power and how often. How many days will yoube away from shore power withouy running engine, etc. Then work out how much juice your indispensable kit requires, and go from there.

 

Power ratings in Watts are written on appliances.

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Just re-read your post. Sorry for rambling.

 

Portable inverters as you describe will produce 240, as previously stated, cables feeding the 12v socket probably not up to purpose.

 

EG: 150Watts at 240V will draw 150/240 0.6 Amps.

 

But, the cable you're plugging your inverter into is 12V.... So, 150/12 is 12 Amps....you could risk melting the cableson the 12V system if they aren't thick enough.

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... the cable you're plugging your inverter into is 12V.... So, 150/12 is 12 Amps....you could risk melting the cableson the 12V system if they aren't thick enough.

More like 15A with inverter losses.

 

Hopefully the 12V feeds are properly fused, so a 16A draw would pop the fuse in short order. There again...

 

Tony

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Many thanks for all the feedback. I think I will contact a man who fits inverters to see what the cost would be. I don't want to risk an electrical fire. I am OK with 240v wiring etc but know nothing about 12v and inverters\amps etc. Sounds like the portable ones are not up to the job.

 

My TV is dual power and has an adapter with the ubiquitous cigarette lighter attachment on the end. I have seen 3pin to lighter and 2 pin to lighter adapter output is @ 10amps and 3 pin @ 2 amps - is either of these of use when plugging in the cool box or TV? I would only run the slow cooker (12v) and cooler when the engine was running so presumably no battery drain?

 

John

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If you know that the wiring and fusing to the 3 pin sockets is up to the job then don't use adaptors - cut off the cigar lighter plug and fit a 3 pin plug. You'll need to experiment with a multimeter to know how the 3 pin sockets are wired anyway, as everyone has their own favourite way of doing it (mine is 'neutral' for +ve and 'earth' for -ve).

 

As for whether the alternator would keep up with demand, yes probably, but what alternator is it? What engine? Do you have an ammeter?

 

Tony

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Where do you get the 3 pin plugs from? I would rather keep the cigarette lighter connection as I use the cooler in the car when travelling back and forward to France. Are the 2 pin adapters with 10 amp out put OK to use or the 3 pin 2amp?

 

I have bought a single Bestek inverter here in France which has a cigarette lighter fixing on one end and French plug socket on the other and using it from the car cigarette lighter it seems to power lamps, laptops, cooler etc. The rated output is 150w so more than enough for laptops\tablets and cooler. What does a 240v fridge require in the way of amps via inverter as we would want to use that on the move?

 

There is an ammeter which generally is all green when checked.

 

John

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You get the 3 pin plugs all over the place but a chandlers would be most convenient for a boater.

 

If you used an adaptor then it would need to be the 10A version. Before using it you would need to check that it's wired the same as your sockets (there is no standard, not even a convention). You would use a multimeter to firstly check that it works (if not you would have to rewire the plug) and secondly to confirm correct polarity.

 

A standard under-counter 240V compressor fridge will probably use around 500W continuous, but start-up surge will be probably three times that.

 

An ammeter that is "all green" is about as much use as a chocolate teapot for battery monitoring purposes.

 

Tony

The only problem with cutting off the cigar plug is they are sometimes fused and the 3 pin plugs are unfused so you would maybe need to fit an inline fuse possibly

Good point :)

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I naively thought a 3 pin plug was a 3 pin plug and would be wired the same as a standard 3 pin 240v plug! Obviously not the case? I wasn't suggesting cutting off the lighter connection, just connecting it via a 3 pin to lighter adapter connector but the only 3 pin ones I have seen are 2amp not 10. There are 2 pin to lighter rated at 10amps but these seem to be 2 square pins?

 

The 3 pin socket holes on the boat look quite small pins. I am of course making the assumption that these are 12v sockets. There are 240v ones but they of course are 3 pin square ones.

 

John

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Where do you get the 3 pin plugs from? I would rather keep the cigarette lighter connection as I use the cooler in the car when travelling back and forward to France. Are the 2 pin adapters with 10 amp out put OK to use or the 3 pin 2amp?

 

I have bought a single Bestek inverter here in France which has a cigarette lighter fixing on one end and French plug socket on the other and using it from the car cigarette lighter it seems to power lamps, laptops, cooler etc. The rated output is 150w so more than enough for laptops\tablets and cooler. What does a 240v fridge require in the way of amps via inverter as we would want to use that on the move?

 

There is an ammeter which generally is all green when checked.

 

John

We use a 12v cooler occasionally. I made up my own adapter for the boat.

You just need a trailing 12 ciggy socket similar to this one:

http://www.ebay.co.uk/itm/12V-Auxiliary-Car-Battery-Terminal-Clip-Cigarette-Lighter-Power-Socket-Adapter-/272320770733?hash=item3f679532ad:g:65cAAOSwl8NVdUG3

 

Chuck the cable away as it is crap, fit a short length of flex and one of these plugs.

http://www.ebay.co.uk/itm/MK-5A-Round-Pin-Plug-White-/131504789701?hash=item1e9e4bd8c5:g:ypoAAOSwyjBW3RqW

 

You can probably get these items cheaper/faster/better quality etc. if you do some research - these are just examples that I found quickly.

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Just a word of warning.

 

Many moons ago I connected our boat fridge (rated at 75 watts) via a cigarette lighter socket (socket rated at 10 amps).

 

After a couple of minutes the cabin was filled with foul smelling smoke.

 

The current draw on start up can be more than 3 times the 'running' wattage - it had melted the lighter plug, socket and attached wiring into a huge black carbonised 'mess'.

It didn't even blow the fuse.

 

Don't bodge or make temporary installations without using the correct (rated) cable and plugs/sockets.

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I naively thought a 3 pin plug was a 3 pin plug and would be wired the same as a standard 3 pin 240v plug! Obviously not the case? I wasn't suggesting cutting off the lighter connection, just connecting it via a 3 pin to lighter adapter connector but the only 3 pin ones I have seen are 2amp not 10. There are 2 pin to lighter rated at 10amps but these seem to be 2 square pins?

 

The 3 pin socket holes on the boat look quite small pins. I am of course making the assumption that these are 12v sockets. There are 240v ones but they of course are 3 pin square ones.

 

John

 

You are comparing chalk with cheese but with possibly a lethal outcome - DC requires only two connections positive and negative, 240v AC mains three, live, neutral and protective earth.

 

If at all possible use dedicated low voltage DC sockets for your 12 volt distribution. For external use suggest these waterproof non-reversible plug/sockets.

 

2302.jpg

 

 

For internal the Hella/DIN range are far superior to the awful although sadly common cigar lighter sockets which are hardly fit for purpose. See Alan 's post above!

 

Car-Charger-Power-Adapter-EU-Socket-Conn

 

The sockets are available as panel or flush side mount. Typical rating 10 amps. Both are available at most chandlers or from mail order marine suppliers.

 

The three round pin connectors I think you were referring to were designed to supply household mains table lights etc. Their rating was 240v 2 amp I believe. Whilst they do the job for DC distribution there is an unused pin and no convention as to which is positive or negative - best stay away IMHO.

Edited by by'eck
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The three round pin connectors I think you were referring to were designed to supply household mains table lights etc. Their rating was 240v 2 amp I believe.

For what it's worth, 5A seem to be the most common on boats.

 

But there were indeed 2A as well - really tiny and we're in chocolate teapot territory again.

 

Tony

Edited by WotEver
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