Inverter Advice

[robertager1962]

I have trawled through the inverter posts on the forum and much of the advice is quite dated (internet is showing its age) so would like some up to date advice please. I am planning on using an inverter for laptop charging etc. My plan is to plug the inverter in to the mains supply plug when required and then remove when shore power is plugged in, thereby avoiding any issues of the inverter and the mains being switched on simultaneously. Crude but simple and I like simple. I have a very old 150 watt inverter but would like to get something a little meatier that I can fit permanently. It is difficult which one to chose as I do not understand the different charging outputs on offer ie square wave, modified wave etc. I think 1000 watt would more than adequate. Can anyone point me in the right direction without breaking the bank please.

 

[pvb]

Why not simply buy a car charger for your laptop and run it off your 12v supply? Much cheaper.

 

[Tranona]

1000w is way OTT for PC charging - although if that is all you want to do then a 12v car type charger is much better as it draws less. Why go up from 12v to 240 and then down to low voltage again? If your "ETCs" are also low powered and you only have a mains charger then a 350w or so is more than adequate.

 

[PaulRainbow]

Easy, do not use an inverter just for laptop charging. Fit a DC-DC converter. An easy solution is something like this :

https://www.ebay.co.uk/itm/TRUST-18...577645?hash=item4888d925ad:g:Dd4AAOSwGotWpJtX

Just as an example, do your own research for pricing, other makes/colours/styles are available. (jusy trying to cover myself with the forum pedants, doubt it will work)

Anyway, chop the plug off and wire it to a switch and fuse/circuit breaker, switch it off when not in use.

You can also run some TV,s sound systems etc from DC-DC converters, i have about five fitted, running different things at different voltages.

 

[PaulRainbow]

Why not simply buy a car charger for your laptop and run it off your 12v supply? Much cheaper.

1000w is way OTT for PC charging - although if that is all you want to do then a 12v car type charger is much better as it draws less. Why go up from 12v to 240 and then down to low voltage again? If your "ETCs" are also low powered and you only have a mains charger then a 350w or so is more than adequate.

I must type faster

 

[robertager1962]

We are planning on living aboard so I am trying to build in some durability. Our laptops range around the 18V mark, so whatever we do would need a step up so would need to be converted to AC at some stage. Unfortunately they are all different makes so would each need a different car charger which may get messy. After reading the forum about electric toothbrushes and square wave inverters, I bought a USB charger for them (yet to arrive) but this started to raise a thorny issue.

 

[robertager1962]

Easy, do not use an inverter just for laptop charging. Fit a DC-DC converter. An easy solution is something like this :

https://www.ebay.co.uk/itm/TRUST-18...577645?hash=item4888d925ad:g:Dd4AAOSwGotWpJtX

Just as an example, do your own research for pricing, other makes/colours/styles are available. (jusy trying to cover myself with the forum pedants, doubt it will work)

Anyway, chop the plug off and wire it to a switch and fuse/circuit breaker, switch it off when not in use.

You can also run some TV,s sound systems etc from DC-DC converters, i have about five fitted, running different things at different voltages.

Thanks for this, really neat. I think this may be worth trying before I do anything else.

 

[PaulRainbow]

We are planning on living aboard so I am trying to build in some durability. Our laptops range around the 18V mark, so whatever we do would need a step up so would need to be converted to AC at some stage.

No you don't. the DC-DC converter does what the name suggests, converts 12v up to the laptop voltage, mine runs at 19v. How do you suppose they would otherwise work from a car fag lighter ?

Unfortunately they are all different makes so would each need a different car charger which may get messy. After reading the forum about electric toothbrushes and square wave inverters, I bought a USB charger for them (yet to arrive) but this started to raise a thorny issue.

If you fit an inverter you'll need to still use the original mains charger for each laptop. Isn't it a bit messy having all of those chargers kicking around ? If you fitted one converter for each laptop, all you have is xx amount of short cables with the plug to fit a particular laptop.

The voltage is selectable, so if you change the laptop for one with a different voltage, just change the setting.

 

[PaulRainbow]

Thanks for this, really neat. I think this may be worth trying before I do anything else.

Just to add, i have one fitted for my laptop, it's about 10 years old and has powered several different laptops. Mine is a Trust one, i'd avoid the cheap Chinese copies.

 

[robertager1962]

No you don't. the CD-CD converter does what the name suggests, converts 12v up to the laptop voltage, mine runs at 19v. How do you suppose they would otherwise work from a car fag lighter ?



If you fit an inverter you'll need to still use the original mains charger for each laptop. Isn't it a bit messy having all of those chargers kicking around ? If you fitted one converter for each laptop, all you have is xx amount of short cables with the plug to fit a particular laptop.

The voltage is selectable, so if you change the laptop for one with a different voltage, just change the setting.

Yes I am definitely sold on your idea, it is a much better solution. Have just bought one (that convinced!)

 

[Richard10002]

The chances are that you will probably want a relatively powerful inverter at some point in the future, so thrashing out the logistics now isnt a bad idea. I have a 2500W Inverter charger, (as well as a separate 60A charger), so I can power some 240V power tools, Dyson upright vacuum, charge shaver and battery for Makita Drill, and other stuff that I cant think of right now.

I like the idea of plugging it into the shore power socket to avoid the possibility of having 2 AC sources into the same circuit. My only concern is that you could end up charging your batteries from the batteries if you forget to turn your charger off and connect the inverter. In addition, it would be a faff to set up each time you wanted to use it, (which could be a good thing, or a bad thing).

My shore power goes into the inverter charger, which then distributes the 240V to the boat circuit/s, and "sends" the charge to the batteries, as appropriate. If shore power isnt connected, there is no way of charging the batteries from the batteries.... however, if shore power fails, the inverter charger automatically reverts to inverter, so can flatten the batteries this way. Some inverter chargers have a switch to set "charger only", but this relies on you remembering to flick the switch. Not easy

 

[RupertW]

No you don't. the DC-CD converter does what the name suggests, converts 12v up to the laptop voltage, mine runs at 19v. How do you suppose they would otherwise work from a car fag lighter ?



If you fit an inverter you'll need to still use the original mains charger for each laptop. Isn't it a bit messy having all of those chargers kicking around ? If you fitted one converter for each laptop, all you have is xx amount of short cables with the plug to fit a particular laptop.

The voltage is selectable, so if you change the laptop for one with a different voltage, just change the setting.

Um, a DC to DC converter does, of course, convert to AC using an inverter, then transforms AC voltage to required DC voltage which it smooths and rectifies to DC at the required voltage. It's hard to see how else it could do the conversion without some very odd circuitry and a lot of waste. What you get though is inverter/transformer/rectifier all in a neat package designed hopefully for minimal power loss in the process.

 

[jdc]

I have something rather different, bit it has worked well for me. I have a 350W inverter producing 110V permanently wired in, ie from a 12V feed via switch on the main panel and to a few strategically placed American sockets. Its no-load power consumption is pretty much negligible so I can leave it on nearly all the time.

The thinking is that 350W is not powerful enough for my normal 220V power tools, or people's hair-driers etc, but is ideal for all those electronic gadgets which guests bring: kindle, laptops, iPads, Smartphones, vibrators, cameras etc etc, not to mention my HH-VHF and Iriduim phone. Without exception the charging 'brick' for all of these takes 100V - 260V so they're all happy. The 110V doesn't get muddled with the normal 13A mains sockets (which run from generator or shore power), and is a bit safer when actually at sea. I'm not sure I'd be happy with all the 13A sockets live nearly all the time.

 

[William_H]

OP asked about square wave ,modified sine wave and pure sine wave inverters. The square wave and "modified sine wave" are a result of the fact that it is far easier to switch power on or off than to smoothly switch it from on to off and back again in a way resembling a sine wave. So a square wave inverter will push out a voltage which rises rapidly to something like 240v then switches off to do the same thing in the negative direction giving an AC which resembles AC mains in terms of total power but is not a sine wave. In fact it contains harmonics of the 50 herz up to quite high frequencies. A modified sine wave (a marketing term) may have some more resemblance to a sine wave but still has lots of square wave effect.
The outcome is that a square wave supply creates havoc in a synchronous motor as found in fans fridges or a drill press with inefficiency and over heating.
They also provide problems to varying degrees with the switch mode power supply in chargers of various sorts TVs etc.
Some people report disasters, some report no problems.
Now more modern technology in inverters can assemble a close to sine wave from many chunks of DC in a fairly efficient manner but more expensive. In case you are wondering all inverters these days use a switch mode converter about 500khz to produce about 380v DC from which the AC wave is assembled.
Square wave inverter is fine for 240v incandescent lights power tools with brush type motor and heating elements.
The bottom line is for general use a pure sine wave is a far safer bet if more expensive.
The main problem is providing DC current with little volt drop from the ships batteries. Most inverters will have a low supply voltage switch off function. At 1500 watts you need around 120 amps at 12v so it does not take much volt drop in cables and switches (or batteries) to cause switch off. There is a tendency for the ignorant to try to operate any 240v appliance on the inverter which just produces disappointment and flat batteries
As said use a DC to DC converter for computers and avoid big inverter if at all possible. OP says he has a small one already just make do with that for occasional use of power tools. ol'will

 

[robertager1962]

OP asked about square wave ,modified sine wave and pure sine wave inverters. The square wave and "modified sine wave" are a result of the fact that it is far easier to switch power on or off than to smoothly switch it from on to off and back again in a way resembling a sine wave. So a square wave inverter will push out a voltage which rises rapidly to something like 240v then switches off to do the same thing in the negative direction giving an AC which resembles AC mains in terms of total power but is not a sine wave. In fact it contains harmonics of the 50 herz up to quite high frequencies. A modified sine wave (a marketing term) may have some more resemblance to a sine wave but still has lots of square wave effect.
The outcome is that a square wave supply creates havoc in a synchronous motor as found in fans fridges or a drill press with inefficiency and over heating.
They also provide problems to varying degrees with the switch mode power supply in chargers of various sorts TVs etc.
Some people report disasters, some report no problems.
Now more modern technology in inverters can assemble a close to sine wave from many chunks of DC in a fairly efficient manner but more expensive. In case you are wondering all inverters these days use a switch mode converter about 500khz to produce about 380v DC from which the AC wave is assembled.
Square wave inverter is fine for 240v incandescent lights power tools with brush type motor and heating elements.
The bottom line is for general use a pure sine wave is a far safer bet if more expensive.
The main problem is providing DC current with little volt drop from the ships batteries. Most inverters will have a low supply voltage switch off function. At 1500 watts you need around 120 amps at 12v so it does not take much volt drop in cables and switches (or batteries) to cause switch off. There is a tendency for the ignorant to try to operate any 240v appliance on the inverter which just produces disappointment and flat batteries
As said use a DC to DC converter for computers and avoid big inverter if at all possible. OP says he has a small one already just make do with that for occasional use of power tools. ol'will

Thanks for this, has really helped to explain in simple terms what the issues are. If I go down this route, I am a little more knowledgeable.

 

[charles_reed]

I have trawled through the inverter posts on the forum and much of the advice is quite dated (internet is showing its age) so would like some up to date advice please. I am planning on using an inverter for laptop charging etc. My plan is to plug the inverter in to the mains supply plug when required and then remove when shore power is plugged in, thereby avoiding any issues of the inverter and the mains being switched on simultaneously. Crude but simple and I like simple. I have a very old 150 watt inverter but would like to get something a little meatier that I can fit permanently. It is difficult which one to chose as I do not understand the different charging outputs on offer ie square wave, modified wave etc. I think 1000 watt would more than adequate. Can anyone point me in the right direction without breaking the bank please.

Not a good idea, to charge through an inverter and normal charger. Cut out the inverter and use a 12v charger.
I've done this for the last 20 years, with a number of laptops and it's never failed.
Far more economical in capital cost and power-usage.
Look here;- https://www.laptopchargerfactory.co...MIuO3L5s603AIVWdwZCh1KVQk9EAAYAiAAEgIJcPD_BwE

 

[jdc]

Not a good idea, to charge through an inverter and normal charger. Cut out the inverter and use a 12v charger.
I've done this for the last 20 years, with a number of laptops and it's never failed.
Far more economical in capital cost and power-usage...

I'm sure you've done it for a good number of years, and it's good to hear that it works well for you, but how have you formed such an emphatic belief that it's 'not a good idea' to use an inverter and normal charger, and thus by implication those who do so have bad ideas and are wrong?

In favour of an inverter:

1. Efficiency
I agree that while better efficiency over-all can be achieved using synchronous rectification in, say, a flyback converter, than can be achieved in the combination of inverter - rectifier - buck converter, it's not that much better (92% versus 92% x 95% of the power being drawn, so about a 5% difference). Whether saving such a small amount of power is material must surely depend on the situation. In my boat, when charging typical laptop battery (4400mAHr at 18V say) I can spare the extra 18 / 12 * 4400 / 1000 * 0.05 = 0.15 AHr from my 12V domestic bank: can't you? That's about 90 seconds from the solar panel...

2. Cost
From the site you provided a A DC-DC converter for laptop charging costs an extra £28.48 on top of other purchases for about a 50W rating, whereas my 350W inverter costs $19.99 (I bought it in the States) but new from Amazon it's £25. An 80W inverter costs only £12.99 from Amazon. So I don't think one can say that your method is 'far more economic'. At most one could say that they are about the same.

3. Convenience
I can charge multiple devices simultaneously, and no fiddly connections to change over depending on laptop model being charged. It also works with a Mac. I can also charge my cordless drill or electric toothbrush, spotlight or run a soldering iron. I have found the convenience of being then able to charge anything outweighs other considerations.

So where am I going wrong?

 

[Tranona]

So where am I going wrong?

Not necessarily wrong.

However the OP just wanted to charge a lap top and a DC/DC charger (which does not need to cost nearly £30 (mine was less than half that) is the most appropriate way. But note my caveat earlier - depends on what the "etc" means. Your "etc" is wide ranging and therefore a more versatile solution is required.

 

[jdc]

Not necessarily wrong...

I had no issue with what you posted; indeed it was very sensible. It is highly likely that for the OP a DC-DC charger is most appropriate - I do him the credit of leaving it to his judgement since he knows his situation.

But for others, who, as you say, may have "etc" reasons, I thought it worth being numerate about the inverter approach's downsides, and concluded that they aren't so big - at least not in my circs - so 'not a good idea' [under any circs] is challengeable.

 

[Tranona]

so 'not a good idea' [under any circs] is challengeable.

Don't think anybody said "under any circumstances". Indeed as I said I have a 350w inverter for other uses, but when I used a PC for navigation (and other things) I used a 12v car charger hard wired.

Now, of course more common to use a tablet so hard wired USB sockets are more useful.