nigelmercier
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YPB?
It's a no brainer. Converting from 12V to 230V then back down to say 18V will double the losses from a direct conversion.
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Small inverter 12v current draw?
- Thread starter LittleSister
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It's a no brainer. Converting from 12V to 230V then back down to say 18V will double the losses from a direct conversion.
Happy Dayz
Well-Known Member
If you follow that earier link it exsplains 'inverter' and its process. early days they were mechanical via a step up transformer - i did not give it that term name.
The term is used in electronic devices, example where a circuit changes (inverts) a voltage to the opposite polarity.
To 'Invert' to me, means to turn something upside down, so the above sort of 'fits' doing it with voltages.
I'd guess the term invertor was used as the process involves reversing (inverting) the input and output connections of a transformer, and stepping up voltage not down also being used.
Remember, we are not restricted by voltage values, rither in or out ss ling as the viltage is increased. its the process used to acheived it that is named as 'inverter'.
To me, 'converter' is to change dc in to a lower output voltage so a device like a phone is not damaged - perhaps 'reverter' would be more consistent term logic?
Todays ' converters' can not deliver a higher voltage without some form of inverter circuit, obviosly acheived electronically today, using possibly a much smaller transformer.
Many terms change or are used to mean something different, to call someone 'gay' used to mean they were of a very happy disposition, but today usually means their sexual orientation and at times used even as an insult or slur.
Alan
nigelmercier
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GHA
Well-Known Member
Unfortunately long since lost the data, but I put a meter on an inverter input and a dc boost converter input both running a laptop , the difference was significant. The cheap inverter pulling about half an amp even with nothing plugged into it.
Like Nigel i can't think of anything onboard which cheap ebay dc converters won't power.
Hydrozoan
Well-Known Member
Depends on the brain involved!
Double the losses then - but double a little is still a little, and I have wondered if the difference is of practical significance.
I have always used a dc-dc converter, but had a bit of trouble identifying a suitable one for a new Compaq laptop with a central pin in the jack. Having finally done so, the converter failed (the first of three I have had to do so) after a bit more than a year. I bought a small inverter as a stopgap but am grafting the jack onto an older converter to see if that will both power the laptop and recharge its batteries. (There is some debate on the web about the precise function and effect of central pins.)
Hydrozoan
Well-Known Member
Thanks - that is interesting, what I had understood and why I have always used a converter. But I did wonder if inverter losses had been reduced such that the difference might be practically insignificant.
nigelmercier
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To put some figures on it, any single conversion will typically be 80-90% efficient, up to 95% in ideal conditions. There are many factors involved, but involving a change from AC to DC or vice-versa will decrease the efficiency. Converting twice is foolish.
RichardS
N/A
As someone says above, don't underestimate the power being drawn by the small inverters even when they are hardly doing anything.
We use a 200W-ish one with a cigar plug (I had to upgrade the fuse but I don't recommend this unless you understand what you are doing) for things that can't be powered by a DC-DC converter (some laptops and mains AC devices) and I now have a rule that, except for emergencies, the thing can only be used when the engines/generator is running as the inverter does a great job of running down my batteries even if it's powering an already fully charged laptop, for example.
Richard
We use a 200W-ish one with a cigar plug (I had to upgrade the fuse but I don't recommend this unless you understand what you are doing) for things that can't be powered by a DC-DC converter (some laptops and mains AC devices) and I now have a rule that, except for emergencies, the thing can only be used when the engines/generator is running as the inverter does a great job of running down my batteries even if it's powering an already fully charged laptop, for example.
Richard
Hydrozoan
Well-Known Member
Thanks, Nigel and Richard. It was certainly quick and convenient to obtain a small inverter as a stopgap, which may come in handy for other purposes anyway, but good to know that my preference for a converter is still justified.
Happy Dayz
Well-Known Member
That's a completely different divice altogether - I'll hand the bridge (rectifier?) back to you then.
Alan
Happy Dayz
Well-Known Member
Fuse is there to protect the cable not the device (which best practice imho has its own fuse).
I'd depending on investigation I'd choose to use a 'slow blow' fuse at the correct current rating, it will stand short duration power surges but blow after about 1 - 2 seconds, depending how much excess current is drawn.
Alan
LittleSister
Well-Known Member
GHA
Well-Known Member
Go on then, what is it you can't run off a dc buck/boost 
chewi
Well-Known Member
Go on then, what is it you can't run off a dc buck/boost
A jigsaw (350W)
A hole saw (in a 550w drill)
both worked off my 600w Maplin inverter when I installed my eberspacher whilst at my mooring.
But I run the laptop off a 12V/19V DC/DC converter, which I suspect is more efficient as others have said, but I have no proof.
I find cigarette lighter sockets thoroughly unreliable, always have to wiggle and check to get a connection.
I am contemplating replacing with XLR sockets, (as used in the audio industry), but also used as a charging connection for my mothers buggy.
RichardS
N/A
Go on then, what is it you can't run off a dc buck/boost
Some laptops will not run off anything unless their manufacturers AC brick unless you mess around soldering capacitors into the power lead ..... and the you invalidate the warranty.
SWMBO's hair straighteners will not run off a DC converter as they are 240V AC. They run off the inverter perfectly.
Richard
Happy Dayz
Well-Known Member
Let's clear this up.
I have been using my iphone, very limited editing facilities, now I'm using my large screen iPad 4. Not much better for cutting text out., so sorry for full posts.
Straight forward observations, I don't know what another might plug in so may need an inverter - which for some needs a 12 volt socket won't be man enough.
Not splitting hairs like you, did I mention 240 volts? While most common option you can (or could at one time likely) get inverters that offer any AC output voltage from 12 volts source upto to your hearts desire. You mention 19 volts where I mention 18 volts, it mattered not for this thread. Most laptops have voltage regulation after the 'brick' while best to keep to makers 'brick' volages, likely actual tolerances are wider. So called auto voltage select after market bricks rely on this, they are not 'intelligent' but likely sense any current overload and shut down.
Why it would use a high frequency sugnal no 50 cycles I do not know, I was not calling a DC -DC converter an inverter, but to achieve 240 volts AC from a DC source to power a'bruck' is quite simply an inverter.
The above post from Richard totally validates my earliest comment to wit "so LIKELY you will still need a plug in inverter.". (My full Post is repeated above).
Those that have cracked on about converters please do re-read the threads title - clue, no mention of 'converters' I can see???
O/P Specifically asked about a small INVERTER (I assume power not size) no mention of CONVERTERS.
Pedantic posts about exacting the definition of wether or not it actually uses an inverter circuit or is a 'converter' were the unhelpful trollings of those who don't have the courtesy to read posts properly , or fail to comprehend the written word, in their head long rush to challenge. I can only assume in a need to feel superior in some way, rather than to actually help with best intentions.
So, as for me being under some kind of 'bridge' and the advice to stop digging' (what ever that meant anyway) I suggest best you take a good look at yourself, there's banter and then there is plain rudeness, I expect an apology and retraction.
Alan
I have been using my iphone, very limited editing facilities, now I'm using my large screen iPad 4. Not much better for cutting text out., so sorry for full posts.
Straight forward observations, I don't know what another might plug in so may need an inverter - which for some needs a 12 volt socket won't be man enough.
Not splitting hairs like you, did I mention 240 volts? While most common option you can (or could at one time likely) get inverters that offer any AC output voltage from 12 volts source upto to your hearts desire. You mention 19 volts where I mention 18 volts, it mattered not for this thread. Most laptops have voltage regulation after the 'brick' while best to keep to makers 'brick' volages, likely actual tolerances are wider. So called auto voltage select after market bricks rely on this, they are not 'intelligent' but likely sense any current overload and shut down.
Why it would use a high frequency sugnal no 50 cycles I do not know, I was not calling a DC -DC converter an inverter, but to achieve 240 volts AC from a DC source to power a'bruck' is quite simply an inverter.
The above post from Richard totally validates my earliest comment to wit "so LIKELY you will still need a plug in inverter.". (My full Post is repeated above).
Those that have cracked on about converters please do re-read the threads title - clue, no mention of 'converters' I can see???
O/P Specifically asked about a small INVERTER (I assume power not size) no mention of CONVERTERS.
Pedantic posts about exacting the definition of wether or not it actually uses an inverter circuit or is a 'converter' were the unhelpful trollings of those who don't have the courtesy to read posts properly , or fail to comprehend the written word, in their head long rush to challenge. I can only assume in a need to feel superior in some way, rather than to actually help with best intentions.
So, as for me being under some kind of 'bridge' and the advice to stop digging' (what ever that meant anyway) I suggest best you take a good look at yourself, there's banter and then there is plain rudeness, I expect an apology and retraction.
Alan
PaulRainbow
Well-Known Member
Yes, lets.
You said
I replied
You then made several posts claiming that my convertor was/is/contained an inverter.
Plain fact is, you misunderstood the difference and misunderstood how to get more than 12v DC from a 12v DC supply.
My posts were not rude by any stretch of the imagination.
GHA
Well-Known Member
Heard about that, Dell isn't it? Though I heard they built in a little chip which talks to the laptop over dallas one wire through the centre pin. What a pain!
Can't say I've had that problem
Worth bearing in mind some varispeed kit like dreamers & drills won't run off cheap investors, you'll need to splash out on a pure sine wave for that.
GHA
Well-Known Member
Let's, this is a sailing forum - to everyone on here an inverter changes 12 or 24 dc to 240ac.
Dc buck or boost converters are completely different animals.
Doesn't matter that many will have a variable frequency inverter running their fridge compressor.
That's the way to world is, if you don't like it tough
https://marinestore.co.uk/Inverters_240_Volt.html
GHA
Well-Known Member
I prefer a genny
The point was more that these days there's less and less need for an inverter onboard, thankfully lots of smaller electronics stuff charges from usb now plus ebay has a multitude of dc buck/boost converters available for any oddities.
Don't suspect, it's true
I went over to Xlr's quite a while ago, a fair bit of work and the price adds up, but they are just streets ahead of those horrible ciggy lighters.