1500w inverter - is modified sine wave ok?

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jfm

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We need to get a 24v - 1500w inverter for my brother's boat.

He wants it to run laptop and charge mobile phones etc on long passages, without need for running genny.

A modified sinewave job is a couple of hundred quid (eg <A target="_blank" HREF=http://www.tlc-direct.co.uk/Products/TLINV1500slash24.html>http://www.tlc-direct.co.uk/Products/TLINV1500slash24.html</A>) whereas a pure sine wave at that power rating is about £1000

So, question is, do we need a pure sine wave? What appliances need a pure sine wave? Resistive loads dont (eg a 1500w kettle) and I guess a mobile phone charger is ok. A laptop runs off DC downstream of the power supply box so I'd guess that's ok, right? So what are the appliances that will only run on pure sinewave?

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You'll be fine with the one you are thinking about! I run everything form muy modified sine wave inverter, including DVD player etc. Although, funnily enough my crews girlfriend has an electronic hair straightener?? Dont ask please! It will not work from the inverter, so I have to start the genny for that! I am a kind skipper! That is the only thing I have found, that does not operate from it.

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here.

I think laptop use could be hit and miss with the modified sine wave version.

<hr width=100% size=1><A target="_blank" HREF=http://www.magnumyacht.net>http://www.magnumyacht.net</A> - Princess P42
 
If the laptop is running through a transformer, which most do, then it will be fine, it only charges the battery.

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Thanks guys. I agree, the laptop runs thru the power pack which converts to the 14vdc or whatever, and I see your point ccscott it really just charges the battery. I think it's worth the gamble to get the <£300 modified sine wave. If it doesn't work we can always ebay it and upgrade to sine wave

Thanks for that link magnum, cheapest 1500w I have seen, and mobitronic is a recognised brand
 
With regards to the laptop power, sine wave is obviously better than modified but there is the option to run it off your boat batteries with a little tweaking.

This which would be better for your laptop in the long term as it's less stressful on the (usually expensive) psu and will provide a perfectly stable voltage. It's also more efficient as your not taking 24 volts upto 240 and back to 15.

This has previously been discussed at length before in the realms on powering laptops directly from 12v batteries which is not relevant to your situation.
You have a 24V system, as I do, and simply fitting a cable with a few 50W resistors to drop from 24 to 15V would provide your PC with an excellent supply.

<hr width=100% size=1>A truly wise man never plays leapfrog with a Unicorn
 
I have a mobitronic, works well, sometimes use it to run Digi box and flat screen with no prob and its only a 1000 watts

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Phil, is your mobitronic a modified sine wave or oure sine wave? - they make both types. MSW would have cost you £2-300, PSW would have been around £800

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using the ship\'s DC batteries

Hmmm. Might give that some thought. I wonder if the laptop's resistance can change suddenly (eg when the screen auto-offs after 5mins inactivity). If it did, the 50W series resistors would suddenly be the wrong load and the voltage drop across the laptop would alter. At least I think it would, maybe I'm mixed up here

I mean it's a proportionate thing, if I recall. If the battery is 24v and I want say 18v for the laptop, then the series resistors must be 1/3 of the resistance of the laptop. If the laptop resistance changes, the series resistor would no longer be 1/3 of the laptop. Any thoughts?

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Re: using the ship\'s DC batteries

As most have said, If you were running a desktop you would need pure... However as it is just charging the battery it won't damage the CPU or mem so you should be ok with a normal

<hr width=100% size=1>Why can't we work 2 days a week and boat the other 5????
 
modified, I use it to avoid putting the genny on if shore power fails. Wouldnt wanna miss Celebrity!!!!

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Re: using the ship\'s DC batteries

I'd give it quite a lot of thought. And then buy the inverter.

Change in charging current will produce a change in voltage presented to charger - as you rightly note. Also dont forget that the resistors are likely to get rather warm - which changes there resistance and hence the charging current.

This is much more likely to do damage than "modified" sine wave.

For simple power applications modification will not make much difference. Assuming a switch mode PSU them may be some affect if odd harmonics of sine wave (modified) are on same frequency as switching in PSU - but thats unlikely.

I can't see you doing any great damage

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