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None Pure Sine inverter and Laptop

I'm buying a boat with a 2000w inverter. It's not pure sine though. What are my limitations with that? Can I use my laptop plugged in to that? Can I charge my laptop while not using it and then run it to flat and recharge it again?
What can you NOT use with a standard inverter?

Asked by: Carl Young  | 11.01pm, Monday 2 July


WW says:

Most modified sine wave (i.e. not pure sine wave) inverters will be able to run laptop power supplies quite well. They also power inductive loads, like drills, sanders, etc. quite well with no issues.
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For laptops, you might have to check that your particular model works well, though I have never had a problem charging various laptops using a simple non-pure sine wave inverter; though I know some people have had issues. The transformer in a laptop powerpack converts the output to DC, so this should be fairly smoothed, even with a vague input; and many powerpacks work on a wide voltage range as well as frequency, so are fairly tolerant. Worth trying out though, just charging first, and then running the laptop.
The only problem comes with sensitive, direct driven 230V appliances like washing machines (due to the thyristor controller), microwaves with digital controls and so on. Though with 2000W available, you wouldn't be able to run a conventional washing machine anyway.
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Some TV's and DVD players might have some slight odd effects when running from a modified sine wave inverter; such as a line or two down the screen, though this does depend partly on the type of TV or DVD player, and the stability of the voltage/frequency of your inverter.
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So, you can run most items and subsitute others (like a microwave with a mechanical timer) from this inverter, but more sensitive electronic loads might not work properly.
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To get the best out of an inverter, make sure the cables from the battery to the inverter are substantial (as at full power, it could be running with a current of over 180amps). Too thin cables, ad you risk voltage drop (which could cause the inverter to sense low voltage too early and cut out), overheating or even fire. For this reason, ensure that there is a large fuse inline, in the positive feed, of around 200 or 250A to cut out the system if it goes wrong.

Mark Langley  | 12.11AM, Tuesday 3 July

With a 2kW modified sine wave invertor you should have no problem running and charging a laptop as they have a switch mode power supply.
It will however put quite a drain on the batteries using such a large invertor for low current loads such as phone and laptop chargers. It is much more efficient to use the 12V supply directly with a vehicle phone charger, and laptop chargers are available which can be set to the voltage required by your laptop.
As Mark says the cables are important, but the batteries and the charging system need to be good for any invertor to work properly.

Rupert Smedley  | 9.31AM, Tuesday 3 July

While we cannot recommend particularly an electrician in the Walsall area, there is one cautionary note about adding new leisure batteries to old ones.
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As batteries get older, the voltage in the cells changes, as the cell chemistry alters (to a point when the battery is effectively dead and won't hold charge). It is often recommended that you do not add new batteries to old ones in the same parallel circuit, as the older batteries can start to affect the new ones, and that you might not have the combined charge that you need.
Depending on the alternator setup on your boat is, you might find a compromise- for instance, if you have twin alternators, you might use the larger one to recharge a new set of domestic batteries, which primarily power the invertor.
You could then add a split charge relay (or, better, a zero-volt loss diode splitter) to charge the engine starter battery and, say, the older leisure battery bank for use by the fridge (which on a boat is usually the second largest electrical consumer after an invertor).
As the smaller engine alternator usually only has to recharge the engine battery, for most of the time it is doing nothing and can be effectively used to charge a couple of domestic batteries.
Just a thought!

Mark Langley  | 12.06PM, Tuesday 3 July


Readers say:

Thanks for that. Unfortunately there are no 12v sockets on the boat as it has been built with the intention of having it permenently Moore with an electric hookup. I need to get some sockets and an extra couple of leisure batteries installed. Anyone know a good electrical in Walsall area?

Carl Young  | 10.13AM, Tuesday 3 July

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