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Living with 12 volts only?


Inverted

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Surely that's very unlikely, inverters aren't 100% efficient are they? I would have thought 20 amps would be the maximum a cheap 300w inverter could pull from the battery.

You've got that backwards. It's precisely because inverters (especially cheap ones) aren't 100% efficient that a 300W inverter could easily draw 30A.

 

Ohm's law p=iv or i=p/v. 300/12.6 =24A. With inefficiencies, 30A.

 

Tony

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That's why I resist the temptation to go any further than a basic 300w unit, in a way it's really just an "adapter" to run things that are low consumption but not 12v friendly.

 

Turntable eh?

 

You'll be needing one of those "Tickover" stickers as well then...

 

Or, I could mount it on a gimbal so it self levels. Or am I just overthinking things ? smile.png

Edited by Inverted
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Everyone wants different things from their boats. Most of my neighbours are highly amused to learn of the large amounts of creature comforts I have on-board, but they are happy with just the basics.

If you are retired and have the time and energy to do things, then you probably won't need so many electrical gizmos.

But I work outside all year round and whilst most things are 12v, tv laptop, tablet, fridge and freezer, I also have a decent battery bank, Solars and a large inverter. I have better things to do with my time than sit in a launderette for hours, for example, so throw my dirty clothes in the machine and do several loads a week, for which i need the inverter.

No one way is right or wrong, just what works for you, I have invested in everything I can afford to make my life easier and for me it works.

  • Greenie 2
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I know three people with record players on narrow boats. They seem to work fine as long as you keep still while they're playing and don't rock the boat. I made one out of Meccano once. Clockwork. The needle I fixed to a Potters catarrh pastille tin box on the arm to amplify the sound. Governing the speed was a problem which I solved with an adjustable rubbing brake. I only had one record though, a 78 called ''Rustles of spring'', which was quite pleasant to listen to, even over and over again at varying speeds, rather appropriate, it having a clockwork motor.

I've also thought about a snooker table on the boat too, like I think Irish Ferries have. Using gyro balls.

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I know three people with record players on narrow boats. They seem to work fine as long as you keep still while they're playing and don't rock the boat. I made one out of Meccano once. Clockwork. The needle I fixed to a Potters catarrh pastille tin box on the arm to amplify the sound. Governing the speed was a problem which I solved with an adjustable rubbing brake. I only had one record though, a 78 called ''Rustles of spring'', which was quite pleasant to listen to, even over and over again at varying speeds, rather appropriate, it having a clockwork motor.

I've also thought about a snooker table on the boat too, like I think Irish Ferries have. Using gyro balls.

You never cease to amaze me cheers.gif

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You never cease to amaze me cheers.gif

Years ago, on one of the TV chat shows was a chap who could look at a records grooves and tell exactly what tune it was. They kept giving him label less records to identify and he was right every time. Wish I could have done that, then I could have just looked at other folks record grooves and go home and listen to them, without buying the records.

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Its still back to having 230 volts AC on board whether it comes from a 13 amp socket in the wall or a box with a cigarette lighter plug on the end

Not that sort of confusion - we were just foolin' around with transposition of formulae. ;) Thanks though! :D

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You've got that backwards. It's precisely because inverters (especially cheap ones) aren't 100% efficient that a 300W inverter could easily draw 30A.

 

Ohm's law p=iv or i=p/v. 300/12.6 =24A. With inefficiencies, 30A.

 

Tony

 

I see, yes that makes sense now. I read somewhere that most inverters are 80% efficient, which sort of tallies with those figures.

 

Having established I know next to nothing about inverters... say your most power hungry 240v appliance is 300w, is it better to have a 300w inverter running flat out or a higher output unit running well within its capacity - which would be more efficient?

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I see, yes that makes sense now. I read somewhere that most inverters are 80% efficient, which sort of tallies with those figures.

 

Having established I know next to nothing about inverters... say your most power hungry 240v appliance is 300w, is it better to have a 300w inverter running flat out or a higher output unit running well within its capacity - which would be more efficient?

Lots of people just suggest thinking of the voltage as 10 volts when you do the sums ie. 10 volts 300 Watts 30 Amps. I wouldn't want it in a cigarette lighter socket at the far end of the boat.

I honestly believe that my Mastervolt 1500 true sine inverter is better than that but I cant prove it.

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Neil2, on 23 Oct 2016 - 5:08 PM, said:

 

I see, yes that makes sense now. I read somewhere that most inverters are 80% efficient, which sort of tallies with those figures.

 

Having established I know next to nothing about inverters... say your most power hungry 240v appliance is 300w, is it better to have a 300w inverter running flat out or a higher output unit running well within its capacity - which would be more efficient?

 

Not 'most' but many are only 80% efficient when running

 

Some are more - 94%, perhaps

Some consume power when not running - which reduces the efficiency even more.

The Victron and others have inverters that reduce the above problems, but they're not cheap.

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Lots of people just suggest thinking of the voltage as 10 volts when you do the sums ie. 10 volts 300 Watts 30 Amps. I wouldn't want it in a cigarette lighter socket at the far end of the boat.

I honestly believe that my Mastervolt 1500 true sine inverter is better than that but I cant prove it.

The 10V thing works two ways - it makes the calculations very simple plus it's nearasdammit 80% of 12.6V.

 

Tony

 

... say your most power hungry 240v appliance is 300w, is it better to have a 300w inverter running flat out or a higher output unit running well within its capacity - which would be more efficient?

The latter. Two reasons:

1. It's never a good idea to run anything flat out (engines, amps, generators etc)

2. Your 300W appliance probably draws a lot more than 300W on start-up.

 

Efficiency isn't relevant to the above. In general you get what you pay for with efficiency. More expensive inverters approach 95% efficient. Cheap ones can be less than 80% efficient.

 

Tony

Edited to add a bit for clarity.

Edited by WotEver
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Living aboard with most things at 12v is fine and no great hardship - but there are a few items and occasions

where it is more difficult. Each one has a solution, but solving them all can be a pain. We had both a travelpower and 3kw inverter but didn't use either very much. The predominant use 240v was for washing machine and a laser printer. Less frequent was various 240v power tools and a food fixer; no doubt alternatives are available but when you already have the gadgets from shore-life you want to use them.

 

There was no solar panels nor generator and we only ran the engine (for battery charging alone) maybe once month; shoreline was only rarely available. It comes back to the cruising and stationary patterns.

 

 

 

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My boat has a Sterling DAI-3000C-12xx, dating back to 2008. This is a 3kW sine wave inverter/solar/charger and has a standby mode that, like one of the earlier replies, doesn't recognise small loads. I've used a very simple solution which is to determine by trial and error what is the lowest power light bulb that will force it to stay on (I found that low wattage low energy fluorescent lamps work best, possibly due to a switch-on surge). I now have a small table lamp positioned in the galley, with a 13W low energy lamp. All I have to do is switch this on if I need to use a low powered device. It seems a little bizarre when explaining to guests, but works well.

 

This makes using the 240V ignition on the hob, the 240V oven fan, and the microwave very straightforward. It's not ideal for things like phone chargers - I usually ask guests to wait until the TV is on in the evening! It's a reasonable solution for short term use, however, and I'm even considering concealing the lamp and wiring it in permanently via a light switch, with just a neon indicator to remind me it's on. Before I did this we ended up lighting the hob with a match as it would only power up if the fridge compressor was running or if the TV was on!

 

By the way, the manual for this inverter/charger that came with the boat was rubbish, and for the wrong model - so I couldn't program it. I've now downloaded the correct manual and edited it to improve the English and correct the errors, so if anyone wants want just let me know.

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It's just a simple task of replacing the PSU with a 12V unit off the shelf. Just google DC-DC ATX PSU

 

ie: http://www.powerstream.com/DC-PC-12V.htm

I looked into this, but look at the prices, 12V $500 vs £80 for an equivalent 240V unit, just to eliminate inverter use, & you'd also need 12V monitor (So think of the difference in price for a 12V TV vs 240V TV)
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Interesting topic, and interesting that no-one seems to follow the model I do...

 

I, like most have a largely 12v system, with a small inverter for those times when we need 240v (for us it's a sewing machine and a printer). But I then have a suitcase generator which comes into play for the washing machine and power tools.

 

This system for us was much cheaper than a powerful inverter, and gives the added benefit of charging the batteries, rather than running them down! We are liveaboards on mooring, and (sadly) don't often get out to cruise. We don't have a hook up and rely on solar for most of our charging.

 

We are also currently renovating a 50' x 10' to house a growing family, and will follow a very similar electrical model. The only difference I am considering is perhaps having a small inverter running 24/7 to power a fridge, giving me access to cheap energy efficient mains powered fridges (i suspect the efficiency gained with an A+++ rated fridge will outway the loss of running an inverter all the time). The alternative is a top loading 12v unit, but even if I DIY this it's looking more expensive...

  • Greenie 1
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Just be aware that the reason for a fridge being A+++ may be partly because its got such thick insulation, so you may get less space for food inside than a lower rated one! We run a Neff 240V fridge with no problems whatsoever. The fridge motor draws sufficient power to take the inverter out of standby mode, although the interior light doesn't, and will flash every few seconds if the compressor's off. Our 240V fridge takes an average of 1.75 Amps (measured over 9 hours at night, with no other electrical equipment on).

 

Also be aware that a TV in standby mode may take sufficient power to keep the inverter running, so make sure you switch off at the socket when not using it. I've checked our TV power consumption and it takes around 44W when on (approximately 4.5 Amps at 12V) - this is a modern 32" flat screen LED TV. The one that came with the boat (same screen size) was an earlier model, not LED technology, and took 4 times as much current and really hammered the batteries! Check the rating panel when you buy one.

 

If you have electronic equipment that will run off a 12V external supply, or has an internal 12V power supply, and is not specifically designed to run off a lead-acid battery, you will probably need to stabilise your battery voltage, as 14.4 volts could be too much for the equipment. Bedazzled sell a couple of 12V-12V stabilisers for LED strips, to avoid flickering and overheating, but when I asked they recommended the larger of the two as being more suitable for supplying other electronic equipment, as it provided a more stable output. Their actual words were:

 

I wouldn't recommend the smaller LVDC24W due to its performance under varying loads however the larger LVDC60W is ideal for anything 12v and (obviously) up to 60W. In fact this power supply is a variant of a range designed to supply power to Televisions and Laptop computers and hence is very suitable for anything on 12v

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We are just 12v day to day, full time liveaboards. We have an inverter, but it only gets used briefly between February and November to use the processor (food processor ) for bread making. In winter I do it by hand unless charging. That's it though. We have a 12v fridge all year round. Laptops, tablets etc happily running via 12v, TV monitor also, all batteries are charged via 12v for ohones, torches etc. We have solar panels, no hook up,a vintage ish engine, air cooled and pathetic at charging via the alternator, and we manage just fine. That said I live with an electronic geek!

Edited by Ally
  • Greenie 1
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