scarlett
Well-Known Member
Just in case you've people hadn't noticed Aldi are selling an inverter for £14.99. It is rated at 150watts continuous, 300 peak and guaranteed for 3 years. Nothing special about it but the price but might come in handy.
Cheap Inverter
- Thread starter scarlett
- Start date
temptress
Well-Known Member
Cheap electronics are just that cheap.
The circutry to convert DC to AC is simple but to do it efficently is difficult and no so cheap.
Ypu can buy very cheap inverters from AUTO shops for £10 or so but they use a large number od DC amps and generate a lot of heat which also take a lot of additional amps.
You get what you pay for.....
The circutry to convert DC to AC is simple but to do it efficently is difficult and no so cheap.
Ypu can buy very cheap inverters from AUTO shops for £10 or so but they use a large number od DC amps and generate a lot of heat which also take a lot of additional amps.
You get what you pay for.....
scarlett
Well-Known Member
Of course you are right. It is unashamedly for occasional use, to charge a small battery, etc. It claims it will operate small power tools, laptops and TVs though I have no plans to use it so.
The spec claims that it has a 90% efficient modified sine wave output. It claims it can be left connected all the time as it has less than a 0.4 amp 'no load 'current draw. I shall not be taking advantage of this feature.
The fact that the supplying company is German and gives a three year guaranttee is of interest to me. If a supplier is that confindent it increases my confidence that it will work for a good while.
The spec claims that it has a 90% efficient modified sine wave output. It claims it can be left connected all the time as it has less than a 0.4 amp 'no load 'current draw. I shall not be taking advantage of this feature.
The fact that the supplying company is German and gives a three year guaranttee is of interest to me. If a supplier is that confindent it increases my confidence that it will work for a good while.
A
Anonymous
Guest
I will come in here with a warning about inverters that do not have *pure* sine waves. I include modified sine wave and square wave inverters....
Most people have heard of 'harmonics'. These are multiples of the 'fundamental' frequency, 50Hz (or 60Hz in the USA). Usually the biggest harmonic from non-sine inverters is at three times the fundamental - i.e. 150Hz. In effect, your non-sine supply is not just giving you (say) 600W at 50Hz, it is also capable of pushing out many tens of watts at 150Hz. Some loads don't mind at all. Ordinary tungsten lamps, soldering irons and other purely resistive loads work just as well at 150Hz as they do at 50Hz but other equipment can malfunction. Sometimes it just doesn't work very well and that isn't a problem - it is obvious and you stop using the inverter to drive that load. unfortunately some equipment contains circuitry that can be damaged by high levels of 150Hz power. For example, some power supply input filters can get very hot and blow up if there is much 150Hz around, after all, they were NEVER designed with that sort of input in mind. The most likely to suffer are high-tech supplies such as computers, TVs, etc. but I have found that my electric toothbrush charger blows up if used with a square wave, and gets hot if used with a modified sine wave.
For myself, I only use a pure sine wave inverter now except one cheap square wave which I use for a couple of bits of kit that really don't mind the difference. I would never, ever use a non-sine inverter with an expensive laptop or PC and when running my laptop from the batteries I use only the pure sine inverter. If you don't want to go down that route I suggest people use only the laptop manufacturer's 12V supply unit, not one of the general purpose 12V dc-dc converters.
While on the subject, I would never consider connecting ship's raw 12V to a laptop direct. Plenty of people seem to get away with it but there are no guarantees and I wonder how many blown laptops have resulted from well-meaning suggestions here and elsewhere.
Most people have heard of 'harmonics'. These are multiples of the 'fundamental' frequency, 50Hz (or 60Hz in the USA). Usually the biggest harmonic from non-sine inverters is at three times the fundamental - i.e. 150Hz. In effect, your non-sine supply is not just giving you (say) 600W at 50Hz, it is also capable of pushing out many tens of watts at 150Hz. Some loads don't mind at all. Ordinary tungsten lamps, soldering irons and other purely resistive loads work just as well at 150Hz as they do at 50Hz but other equipment can malfunction. Sometimes it just doesn't work very well and that isn't a problem - it is obvious and you stop using the inverter to drive that load. unfortunately some equipment contains circuitry that can be damaged by high levels of 150Hz power. For example, some power supply input filters can get very hot and blow up if there is much 150Hz around, after all, they were NEVER designed with that sort of input in mind. The most likely to suffer are high-tech supplies such as computers, TVs, etc. but I have found that my electric toothbrush charger blows up if used with a square wave, and gets hot if used with a modified sine wave.
For myself, I only use a pure sine wave inverter now except one cheap square wave which I use for a couple of bits of kit that really don't mind the difference. I would never, ever use a non-sine inverter with an expensive laptop or PC and when running my laptop from the batteries I use only the pure sine inverter. If you don't want to go down that route I suggest people use only the laptop manufacturer's 12V supply unit, not one of the general purpose 12V dc-dc converters.
While on the subject, I would never consider connecting ship's raw 12V to a laptop direct. Plenty of people seem to get away with it but there are no guarantees and I wonder how many blown laptops have resulted from well-meaning suggestions here and elsewhere.
Ships_Cat
Well-Known Member
I think you are being very alarmist except perhaps for the el cheapo "junk" inverters (but I could not comment on them as I have never used them).
We have and continue to run all types of equipment off respected brand "modified" sine wave inverters and have never had any issues whatsoever as long as the load was within the capabilities of the inverter. That includes running 230v powered radio equipment of various types and services (MF, HF, TV), various computers (both laptop and desk top, laser printers, etc), various power tools and household appliances.
With respect to the 12 volt dc "step up" power supplies for computers, I have tested a number of the cheap ones of these - the types that use buck converters (which I think will include any "step up" supply on the market eg the 12 v dc to 16, 18, 19, etc volt dc ones) are all rock steady and clean over all the 12 volt supply excursions possible to be found on a yacht. I have had one fail but it failed to the safe mode of 12 volts output.
Also, I have never had a problem of any sort whatsoever running 12 volt equipment directly off the boat's 12 volt supply, including notebooks. But ones own confidence in that area is probably entirely dependant on the quality of the 12 volt supply systems one has on board.
John
We have and continue to run all types of equipment off respected brand "modified" sine wave inverters and have never had any issues whatsoever as long as the load was within the capabilities of the inverter. That includes running 230v powered radio equipment of various types and services (MF, HF, TV), various computers (both laptop and desk top, laser printers, etc), various power tools and household appliances.
With respect to the 12 volt dc "step up" power supplies for computers, I have tested a number of the cheap ones of these - the types that use buck converters (which I think will include any "step up" supply on the market eg the 12 v dc to 16, 18, 19, etc volt dc ones) are all rock steady and clean over all the 12 volt supply excursions possible to be found on a yacht. I have had one fail but it failed to the safe mode of 12 volts output.
Also, I have never had a problem of any sort whatsoever running 12 volt equipment directly off the boat's 12 volt supply, including notebooks. But ones own confidence in that area is probably entirely dependant on the quality of the 12 volt supply systems one has on board.
John
scarlett
Well-Known Member
Regarding your good warning regarding the use of the inverter with a laptop, regardless of the further inefficiencies introduced, could the inverter be used with an included mains adaptor to overcome the frying with too many cycles?
I used to have a terrible laptop which demanded 19 volts. Other gadgets all seem to work off a mains adaptor supplying 6 volts or similar. Both types of adaptor get very hot. The laptop got so hot one needed a magazine on ones lap to prevent burns! It was not cheap either, costing £2000 in 1993. I would expect the mains adaptor converting stuff back to DC to overcome the cycles problem but I am obviously no expert.
Is there a way a layman can check [ in a non destructive way!] for the harmonics about which you warn? I only have a simple amp, volt and ohm meter. If the instructions say it can be used with a laptop or TV, maybe they have fitted circitry sophisticated enough to enable such uses.
I used to have a terrible laptop which demanded 19 volts. Other gadgets all seem to work off a mains adaptor supplying 6 volts or similar. Both types of adaptor get very hot. The laptop got so hot one needed a magazine on ones lap to prevent burns! It was not cheap either, costing £2000 in 1993. I would expect the mains adaptor converting stuff back to DC to overcome the cycles problem but I am obviously no expert.
Is there a way a layman can check [ in a non destructive way!] for the harmonics about which you warn? I only have a simple amp, volt and ohm meter. If the instructions say it can be used with a laptop or TV, maybe they have fitted circitry sophisticated enough to enable such uses.
A
Anonymous
Guest
The harmonics that I have referred to are always present in modified sine and square wave inverters. Pure sine wave inverters should have very low levels of harmonics but by their very nature there will be some harmonics so it is best to go for a good quality model.
Modified sine wave inverters should have a lower level of 150 Hz harmonic than the (usually cheaper) square wave inverters but greater levels of higher harmonics, notably 250 Hz. Without full design information about the load, it is not possible to predict what effect the harmonics will have. The effect could be anything from zero to immediate destruction.
All I can say with a reasonable degree of certainty is that computer and TV supplies, etc., are all designed and specified to be powered from a sine wave supply (i.e. an ordinary mains supply). If they should fail due to use with square or modified sine wave inverters no doubt the manufacturers would refuse to repair under warranty.
As for inverter manufacturers claiming that their products are suitable for TVs, PCs, etc., then maybe you would have some comeback but since most of them seem to be unbranded and 'Made in China', the chances of getting them to repair your £2000 laptop must be verging on zero. Your risk, but I don't do it, and I have been down that path. I am (or was) an electronics engineer and have designed switch-mode power supplies, so I do understand the issues.
Those folk in this and other forums, who say that they are qualified to give an opinion, and tell you that it is safe to use non-sine inverters to drive sophisticated equipment, are leaving themselves open for a claim against them. It would be wise to ensure that you have their actual contact details and their confirmation that they do accept responsibility before you take their advice. Chances are they are not qualified electronics engineers in any case. And if they are, they might not want to take on the responsibility for the consequences of their 'professional' advice.
Modified sine wave inverters should have a lower level of 150 Hz harmonic than the (usually cheaper) square wave inverters but greater levels of higher harmonics, notably 250 Hz. Without full design information about the load, it is not possible to predict what effect the harmonics will have. The effect could be anything from zero to immediate destruction.
All I can say with a reasonable degree of certainty is that computer and TV supplies, etc., are all designed and specified to be powered from a sine wave supply (i.e. an ordinary mains supply). If they should fail due to use with square or modified sine wave inverters no doubt the manufacturers would refuse to repair under warranty.
As for inverter manufacturers claiming that their products are suitable for TVs, PCs, etc., then maybe you would have some comeback but since most of them seem to be unbranded and 'Made in China', the chances of getting them to repair your £2000 laptop must be verging on zero. Your risk, but I don't do it, and I have been down that path. I am (or was) an electronics engineer and have designed switch-mode power supplies, so I do understand the issues.
Those folk in this and other forums, who say that they are qualified to give an opinion, and tell you that it is safe to use non-sine inverters to drive sophisticated equipment, are leaving themselves open for a claim against them. It would be wise to ensure that you have their actual contact details and their confirmation that they do accept responsibility before you take their advice. Chances are they are not qualified electronics engineers in any case. And if they are, they might not want to take on the responsibility for the consequences of their 'professional' advice.
Ships_Cat
Well-Known Member
The ac adapter for your computer will certainly be a switch mode supply. What it does, in simple terms, is create high voltage DC then lowers that by chopping it into a square wave and then recovering the DC through a low pass filter. If you look at that you will see that is basically how a modified square wave invertor works but in reverse (including the square wave bit), so go figure about the warnings about harmonics from modified square waves.
As in my last post, the step up DC supplies (eg to the 19 volts you mention) seem to be able to be relied upon, even the cheap ones. Again, they are switch mode devices producing square waves as part of the conversion process so it seems if you are to follow the advice that square wave devices are to be avoided and you also should not use the 12 volts on board as a direct supply, then one is completely out of luck for being able to power notebooks on board.
The fact that your notebook runs hot is no indication of a problem unless it is different if one runs it on a shore supply. Some notebooks and their power supplies run very hot in the manner you state (including when on shore) others seem to run much cooler - on I have recently bought runs very cool itself but its AC power supply runs very hot (those whether ashore or aboard), and if I power it from an adequately supplied DC step up supply on board that runs very cool.
If I was making the choice between el cheapo invertor and a buck converter DC supply I would steer away from el cheapo inverters (but not from name brand modified square wave ones which will not be so cheap, but cheaper than a sine wave one) and use a cheap "step up" DC supply but it must be of adequate capacity (some notebooks draw more than the 65 watts that the cheaper supplies are commonly rated at).
John
As in my last post, the step up DC supplies (eg to the 19 volts you mention) seem to be able to be relied upon, even the cheap ones. Again, they are switch mode devices producing square waves as part of the conversion process so it seems if you are to follow the advice that square wave devices are to be avoided and you also should not use the 12 volts on board as a direct supply, then one is completely out of luck for being able to power notebooks on board.
The fact that your notebook runs hot is no indication of a problem unless it is different if one runs it on a shore supply. Some notebooks and their power supplies run very hot in the manner you state (including when on shore) others seem to run much cooler - on I have recently bought runs very cool itself but its AC power supply runs very hot (those whether ashore or aboard), and if I power it from an adequately supplied DC step up supply on board that runs very cool.
If I was making the choice between el cheapo invertor and a buck converter DC supply I would steer away from el cheapo inverters (but not from name brand modified square wave ones which will not be so cheap, but cheaper than a sine wave one) and use a cheap "step up" DC supply but it must be of adequate capacity (some notebooks draw more than the 65 watts that the cheaper supplies are commonly rated at).
John
A
Anonymous
Guest
Right-oh, you carry on telling people that they will not have any problems, which fact you know for sure as you have not personally had any problems. Very scientific and professional, I don't think.
Are you offering compensation to those unfortunates who take your advice and who, as a consquence, find their electronic equipment has been damaged?
Are you offering compensation to those unfortunates who take your advice and who, as a consquence, find their electronic equipment has been damaged?
Ships_Cat
Well-Known Member
Now you are getting really silly /forums/images/graemlins/frown.gif
There are tens of thousands of notebooks out there on boats quite happily run off modified square wave inverters or cheap buck converters - you are saying that they are all doing the wrong thing. /forums/images/graemlins/crazy.gif
Also, despite your advice to the contrary, I have had a TV (Sony) run on board my own boat off a modified sine wave supply repaired by the manufacturer under warranty after it developed a power supply problem (unrelated to an inverter). The supplier knew it had been on a boat and was totally disinterested in that fact.
Also, on new builds I manage, we have had the occasional item of AC powered non marine new equipment fail (eg HiFi component) and the supplier is never interested in the fact it came off a boat (often they know as they will have sourced the equipment especially for the boat eg specially sourced 110v equipment to go on board a boat being built in a 230v country, or vice versa).
I do agree, if you buy no name TV's and other equipment then you can't expect the same back up - ashore or afloat, inverter or no inverter.
{Edit: do I not recall that you also advise not using a DC supply to power ones notebook if one is using a SSB transmitter because you blew yours up? Again an area most of us, apparantly with qualifications and experience which you claim do not match your own, have no problems in}.
John
There are tens of thousands of notebooks out there on boats quite happily run off modified square wave inverters or cheap buck converters - you are saying that they are all doing the wrong thing. /forums/images/graemlins/crazy.gif
Also, despite your advice to the contrary, I have had a TV (Sony) run on board my own boat off a modified sine wave supply repaired by the manufacturer under warranty after it developed a power supply problem (unrelated to an inverter). The supplier knew it had been on a boat and was totally disinterested in that fact.
Also, on new builds I manage, we have had the occasional item of AC powered non marine new equipment fail (eg HiFi component) and the supplier is never interested in the fact it came off a boat (often they know as they will have sourced the equipment especially for the boat eg specially sourced 110v equipment to go on board a boat being built in a 230v country, or vice versa).
I do agree, if you buy no name TV's and other equipment then you can't expect the same back up - ashore or afloat, inverter or no inverter.
{Edit: do I not recall that you also advise not using a DC supply to power ones notebook if one is using a SSB transmitter because you blew yours up? Again an area most of us, apparantly with qualifications and experience which you claim do not match your own, have no problems in}.
John
scarlett
Well-Known Member
To sum up the combined brains of the experts here and for the benefit of others, if I have understood correctly:-
I can use it with impunity on simple loads like small electric drills and to charge battery powered tools like an 18 volt electric drill or a 6 volt screwdriver
I am taking a big risk plugging it into something like a laptop or TV,. It might work or it might immediately destroy the the power control circitry within the TV or laptop.
It is certain to damage a device used to charge the battery in a toothbrush where the charger induces the charging effect.
Have I understood?
And what ways of there to check for the purity of the sine wave output? For example, will the AC volt measuring circuitry of my simple meter still measure an impure output? Or will I destroy the meter?
I can use it with impunity on simple loads like small electric drills and to charge battery powered tools like an 18 volt electric drill or a 6 volt screwdriver
I am taking a big risk plugging it into something like a laptop or TV,. It might work or it might immediately destroy the the power control circitry within the TV or laptop.
It is certain to damage a device used to charge the battery in a toothbrush where the charger induces the charging effect.
Have I understood?
And what ways of there to check for the purity of the sine wave output? For example, will the AC volt measuring circuitry of my simple meter still measure an impure output? Or will I destroy the meter?
A
Anonymous
Guest
Not quite. Can we please firstly summarise the nature of the problem. Anything designed for use on the mains will have been designed with a certain voltage, frequency and total harmonic distortion content in mind. Some designs are almost totally immune to harmonics whereas others can be critical. In some cases all you get is poor performance (e.g. funny colours around the edge of the TV) and in other cases components get overloaded by the harmonics. Typically, input filters that are put in to filter out unwanted mains signals can get very hot because they are doing their job...it's just that the designer did not take into account the possibility that some clot would use his product on a square wave (or similar) instead of a sine wave!
Let me add that sometimes this problem will surface after many hours of use. If the components are getting hot, eventually they will fail.
Ordinary electric drills without electronic speed control are OK but it is possible that some drills could be harmed if they have electronics. Anything with a battery charger is a potential problem though some chargers won't be a problem. The problem is which ones? Nobody can tell you unless they have the circuits and design parameters and the knowledge and skill to give an opinion.
It is certain to damage Braun electric toothbrush chargers of the same type as mine. However, there is nothing to stop Braun introducing a new design at any time which might be fine. Similarly, your neighbour might have been using a product on square or modified sine for ages without a problem buy you go out and buy one that looks the same on the outside but has a different design on the inside. With the Braun toothbrush I suspect that the charger has a reactive device in series with the mains to act as a current limit which, at 250Hz, becomes quite a low impedance, letting a highish current flow. That's just an educated guess, there are other possibilities.
As for checking the waveform purity, you won't damage the meter (as long as you use it on the correct range, of course!) but you won't learn very much. Without looking at the spec of the meter in question it isn't possible to tell (but I get the feeling that some bright spark is going to tell us that he can /forums/images/graemlins/smile.gif). There are some very nice little scope-cum-multimeters available which would tell you immediately but you wouldn't buy one of those unless you were an electronics engineer or a keen amateur.
The real answer is to get a sine wave inverter then you won't go wrong. They are more expensive, heavier and larger but they are better. Look at it this way, why would people buy sine wave inverters if cheap square and modified sine inverters would suffice?
Let me add that sometimes this problem will surface after many hours of use. If the components are getting hot, eventually they will fail.
Ordinary electric drills without electronic speed control are OK but it is possible that some drills could be harmed if they have electronics. Anything with a battery charger is a potential problem though some chargers won't be a problem. The problem is which ones? Nobody can tell you unless they have the circuits and design parameters and the knowledge and skill to give an opinion.
It is certain to damage Braun electric toothbrush chargers of the same type as mine. However, there is nothing to stop Braun introducing a new design at any time which might be fine. Similarly, your neighbour might have been using a product on square or modified sine for ages without a problem buy you go out and buy one that looks the same on the outside but has a different design on the inside. With the Braun toothbrush I suspect that the charger has a reactive device in series with the mains to act as a current limit which, at 250Hz, becomes quite a low impedance, letting a highish current flow. That's just an educated guess, there are other possibilities.
As for checking the waveform purity, you won't damage the meter (as long as you use it on the correct range, of course!) but you won't learn very much. Without looking at the spec of the meter in question it isn't possible to tell (but I get the feeling that some bright spark is going to tell us that he can /forums/images/graemlins/smile.gif). There are some very nice little scope-cum-multimeters available which would tell you immediately but you wouldn't buy one of those unless you were an electronics engineer or a keen amateur.
The real answer is to get a sine wave inverter then you won't go wrong. They are more expensive, heavier and larger but they are better. Look at it this way, why would people buy sine wave inverters if cheap square and modified sine inverters would suffice?
Ships_Cat
Well-Known Member
Look at it this way, why would people buy sine wave inverters...
Most don't because modified sine wave inverters (possibly excluding the el cheapo ones) do suffice.
You have said that you should not use such inverters for powering a notebook or other equipment, nor should you use a buck converter (DC step up) supply and nor should you run the notebook direct off the boat's 12 volt supply. Which means you are saying that you can only use a more expensive "pure" sine wave inverter.
Given that the vast majority of notebooks (and other equipment) on boats (and often in cars, etc) are run off the supplies you reckon are no good, and that without problems, I think most will see the absolute silliness of your requirement and will not be led astray.
John
Most don't because modified sine wave inverters (possibly excluding the el cheapo ones) do suffice.
You have said that you should not use such inverters for powering a notebook or other equipment, nor should you use a buck converter (DC step up) supply and nor should you run the notebook direct off the boat's 12 volt supply. Which means you are saying that you can only use a more expensive "pure" sine wave inverter.
Given that the vast majority of notebooks (and other equipment) on boats (and often in cars, etc) are run off the supplies you reckon are no good, and that without problems, I think most will see the absolute silliness of your requirement and will not be led astray.
John
A
Anonymous
Guest
[ QUOTE ]
Given that the vast majority of notebooks (and other equipment) on boats (and often in cars, etc) are run off the supplies you reckon are no good, and that without problems, I think most will see the absolute silliness of your requirement and will not be led astray
[/ QUOTE ]Many sensibly buy the power supplies sold by their laptop manufacturers. Others sensibly buy pure sine wave inverters. Some people are prepared to take a chance by using supplies that give an output totally outside the requirements specified by their laptop manufacturer. Good luck to 'em but I doubt whether many of them know the size of risk they are taking.
The only possible reason for buying a cheap inverter (or a cheap dc-dc converter not approved by the laptop manufacturer) is to save money. It could be a very false economy. I like to save money where I can but this is one area where I no longer try to economise. It is just not worth it.
Given that the vast majority of notebooks (and other equipment) on boats (and often in cars, etc) are run off the supplies you reckon are no good, and that without problems, I think most will see the absolute silliness of your requirement and will not be led astray
[/ QUOTE ]Many sensibly buy the power supplies sold by their laptop manufacturers. Others sensibly buy pure sine wave inverters. Some people are prepared to take a chance by using supplies that give an output totally outside the requirements specified by their laptop manufacturer. Good luck to 'em but I doubt whether many of them know the size of risk they are taking.
The only possible reason for buying a cheap inverter (or a cheap dc-dc converter not approved by the laptop manufacturer) is to save money. It could be a very false economy. I like to save money where I can but this is one area where I no longer try to economise. It is just not worth it.
fourtheleas
New Member
U will need min of 500w, 800w max. i got from a Uk non yachtly internet site 3yrs ago(£50) no faults, use every other day for 2.5yrs.