Pure Sinewave Inverter - inexpensive!

fireball said:
Jeeze ... come on here and point out what I consider to be a good price for a usually expensive device from a reputable retailer and get all the negatives about it ...
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Maplin, reputable retailer? Their kit is OK, but often way over-priced.

I've got an inverter on my boat. The only time it is ever used is when a guest only brings a mains charger, and I don't already have a 12V one. Going from DC to 230V AC and back to DC is madness.
 
nigelmercier said:
Maplin, reputable retailer? Their kit is OK, but often way over-priced.
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Yes - a reputable retailer - they have a reputation ... and it's reasonable. They've also been around for a long time and I'd have confidence in buying most things from them. With regards to price - yes, they're often "over priced" - but this wasn't .. hence I brought it to everyones attention.

nigelmercier said:
I've got an inverter on my boat. The only time it is ever used is when a guest only brings a mains charger, and I don't already have a 12V one. Going from DC to 230V AC and back to DC is madness.
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it isn't madness - it may not be ideal, but it's not madness - it depends what you want to power.
With 3 different laptops, external harddrives (that require power), wifi access points in electronics plus other devices (such as the slow cooker) an inverter becomes a sensible option rather than doubling up on the power adapters required (usually only short term)
 
Norman_E said:
This is pretty cheap for a pure sine wave inverter of that size, but be aware of two things. Firstly its maximum short term output is 1200 watts. The best inverters have a maximum short term output of about 1.5 times rated output, which is important if you use it to start inductive loads like motors and fridge compressors some of which need a start up current of more than three times their running consumption. Secondly pure sine wave inverters are inherently less efficient than the modified sine wave or square wave types. The best are over 90% efficient, that one is 85%. Not terrible, but it means that at 1000 watt output it will be pulling almost 100 amps out of your battery bank.
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yup - worth noting the output - the peak is actually 2kw with 1.2kw being the longer short term load (haven't got the docs with me - but I think it was in the 10's of minutes).
100amp would kill our battery PDQ - I don't intend to try - but it's nice to know the capability is there - the next option down was 300w which would've sufficed, but all the thresholds are lower and as the 1kw wasn't overly more expensive I considered it worth the spend.

I wouldn't think you really want to run a fridge off one - unless you've got seriously huge charging capacity !
 
oldvarnish said:
I suspect my Apple computer prefers a sine wave
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fergycool said:
I'm after a inverter for a 2013 Macbook Pro charger.

Any advice on whether that needs pure or modified sine wave?

Cheers
Ferg
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That was the key for changing my inverter - I have a 100w (or was it 150w) can inverter - modified sinewave - drives a fan no problem, plug the MBPro in and it doesn't charge plus you can hear strange ticks and clicks from the power pack.
Ideally you'd want a 12v adapter for it, but as the new version of MBPros use a different adapter plus I'd got other kit to power it wasn't worth the spend for me - but worth a consideration ...
 
I've always been told that you can't up-transform DC voltage and that these so called DC-DC converters actually go through DC-AC-DC in order to do this. Not that I know anything about it myself!*



*Wikipedia disagrees and I'm wrong it seems.
 
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Storyline said:
Excuse my ignorance but is the charger more likely to get damaged with a modified sine wave rather than the laptop itself ?
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I think it quite unlikely you'd damage the laptop itself, unless the charger was a really shoddy item.

The Braun toothbrush is a very special case, they use the mains to induce current in a coil in the brush, so putting in anything other than the sinewave it's designed for is asking a lot.
Most things like laptop chargers just take the mains and rectify it, then transform it at a higher frequency, because that allows a smaller transformer. That should not be sensitive to waveform, but things like noise suppression, surge arrestors and power factor correction can cause problems.
Inside the laptop there will be at least one more dc/dc conversion to generate the 3.3V etc that they run from.
 
Surely it would not be hard to rig up a dc-dc converter to get a voltage of the maximum likely to be required and then have it steped down to a series of useful voltages. You could even put on an array of standard plugs. That way you simply select the voltage required for your device, pick the correct plug and off you go. Obviously you would need to be careful not to put it to the wrong setting. There are lots of variable DC power supplies and even simple online tutorials on how to make your own. The only bit you would be replacing is the transformer and rectifier down from 240v with a simple dc booster.
 
oldvarnish said:
Not from me. I was grateful for the posting, and regret they'd sold out before I got there.

Sometimes I think you could post a ham sandwich on here and sooner or later someone would come along and give you twenty good reasons why it's a threat to your safety at sea.
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Did you see the programme on telly last night about how processed meats can lose you 5 years of your life....... ;)
 
lw395 said:
...The Braun toothbrush is a very special case, they use the mains to induce current in a coil in the brush, so putting in anything other than the sinewave it's designed for is asking a lot....
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That's a very good example. I've been through three Brauns, and each time they replaced them FoC within two years of manufacture, even without the original receipt. There is a code on them to identify the date.

Now I'm having to use my 2Kw pure sine wave Victron inverter just to charge my toothbrush!!!!!
 
sailinglegend420 said:
That's a very good example. I've been through three Brauns, and each time they replaced them FoC within two years of manufacture, even without the original receipt. There is a code on them to identify the date.

Now I'm having to use my 2Kw pure sine wave Victron inverter just to charge my toothbrush!!!!!
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My toothbrush is kinetic powered from the movement of your forearm.
 
fireball said:
I wouldn't think you really want to run a fridge off one - unless you've got seriously huge charging capacity !
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My fridge has a mains compressor and was run through a CLD inverter. It was a system fitted to a lot of charter boats in the Med because it provides powerful cooling. The inverter was an 800 watt continuous power job with automatic detection of shorepower and automatic switchover. To cope with it a bigger alternator (110 or 120 amp) was also fitted. My CLD inverter has burned out and cannot be fixed so I am installing a new Sterling Power 1800 watt inverter and my own wiring with a changeover switch and a relay to start the compressor when the 12 volt circuit that drives the cooling water pump is switched on by the fridge thermostat. The original relay was part of the CLD inverter. As you have clearly worked out it is better to have too much inverter capacity than too little, current drawn from the 12 volt batteries is roughly proportional the mains current being drawn so greater capacity only really costs in terms of initial outlay. Just size the 12 volt cables to the inverter to cope with maximum demand and keep them as short as possible.
 
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