Jump to content

Modified sine wave inverters


Col_T

Featured Posts

So the boat has a Sterling modified sine wave inverter, which worked for everything 240v until I got a new laptop (an Acer Swift thingie). The Acer doesn't charge from the boat 240v electrics, but does charge from the national grid 240v electrics, unsurprisingly.

 

Is there a gadget of some kind that can take a modified sine voltage and convert it into a pure sine wave? I suspect the answer is 'no', and my options are replace the Sterling or just not take the laptop onto the boat, which would be a shame as we intended to use it as a DVD player.

 

Link to comment
Share on other sites

My Acer lap-top is 19v.

 

I purchased (from ebay) as 12v to 19v converter - it plugs into a cigarette ligher socket and runs the lap-top with no problems.

 

Look at your mains charger and check two things :

1) Type of plug that connects to the lappy

2) How many watts / amps is the transfomer ?

 

Choose your 12v - 19v adapter to suit the answer to the two questions.

 

Mine is ;

 

DC Adapter 90w

Input 11-15v Max 10 amps

Output 19v - 4.74 amps

Made in china

Link to comment
Share on other sites

14 minutes ago, TheBiscuits said:

Or failing that get a little pure sine wave inverter to run the laptop.  150w should be plenty.

The price difference between horrible modified sine wave inverters and pure sine wave seems to have dropped a lot in recent years. A small pure sine wave inverter isn't terribly expensive these days.

Link to comment
Share on other sites

As usual, I forgot to include a piece of 'useful' information, specifically that the transformer for the laptop outputs 19vDC, 3.42A, 65.0W.

I'll have a look for the 12v => 19v adapter that @Alan de Enfield mentions.

 

On the subject of an inverter specifically for the laptop, are there any issues with having two inverters connected to the same battery bank - the Sterling and a small pure sine wave one for the laptop?

Link to comment
Share on other sites

All covered above for 12v DC-DC power supplies or a little pure sine inverter, but in case you’re interested, the gadget to convert modified sine/dirty mains into a pure regulated waveform is a specific type of uninterruptible power supply, designed for critical IT systems. Most UPSs are basically a charger, battery and inverter in a box with a relay to switch over very fast between mains power and inverter power, which doesn’t actually condition the power. Full cycle UPSs first convert the dodgy mains to 12v to charge the batteries, then have an inverter which is running all the time. These are very good at cleaning up dirty power, for the touring equipment racks at work we use them as they’re often run from generators or iffy site power. 
 

Also - no problem having two inverters, as long as you don’t connect their outputs at any time, eg plug both into your 240v circuit. This will blow up one of them, and if the inverters have a standard 13a outlet, one plug will have live pins! If you have chunky wiring to the 12v sockets in the boat, you could buy a little inverter to connect to the 12v socket when you need the laptop. Otherwise you’d need to install a changeover switch for the two inverters, by which point you may as well buy a big pure sine inverter.

 

If you’re using a 12v to 19v converter (the best thing in my opinion) don’t get the mega cheap ones which look a bit like a CB radio mic. They have poor filtering on the output side, no protection and often run very hot. 

Edited by cheesegas
Link to comment
Share on other sites

10 minutes ago, cheesegas said:

All covered above for 12v DC-DC power supplies or a little pure sine inverter, but in case you’re interested, the gadget to convert modified sine/dirty mains into a pure regulated waveform is a specific type of uninterruptible power supply, designed for critical IT systems. Most UPSs are basically a charger, battery and inverter in a box with a relay to switch over very fast between mains power and inverter power, which doesn’t actually condition the power. Full cycle UPSs first convert the dodgy mains to 12v to charge the batteries, then have an inverter which is running all the time. These are very good at cleaning up dirty power, for the touring equipment racks at work we use them as they’re often run from generators or iffy site power. 

 

Technically correct, but a pure sine inverter replacement would probably be cheaper and more efficient!

 

 

  • Greenie 1
Link to comment
Share on other sites

I have a 16 year old Sterling 1800w modified sine wave inverter and every laptop I've owned during that period has run and charged from the inverter without a problem.

 

The only things that don't like the inverter are the microwave and the electric toothbrush!

Edited by blackrose
Link to comment
Share on other sites

Just now, blackrose said:

I have a 16 year old Sterling 1800w modified sine wave inverter and every laptop I've owned during that period has run and charged from the inverter without a problem.

 

That doesn't help Col with his new laptop that won't work despite everything else having worked for ages.

 

I'll bet your laptop power bricks get quite warm too.

Link to comment
Share on other sites

For some UPS supplies, the invertor only operates when mains is lost. I have an APC UPS that operates in this way. I actually run it disconnected from the mains and powered  from a 23A 12V battery charger floated across its 12V battery, having modified it to provide a variable frequency mains supply for adjusting the speed of a synchronous motor.  It was supplied with a manual and a circuit diagram, showing the electro-mechanical relay that switches from straight through to invertor when mains is lost, and back again when mains is restored. n.b. I have to float it across a 12V battery because the battery charger is a smart one that only produces an output when it detects that a battery is present for it to supply electricity to.  The 12V battery would not be necessary if operated from 12V boat electrics.  

Edited by Ronaldo47
12V battery comment added
Link to comment
Share on other sites

@cheesegas

UPS stuff - that's interesting and not something I knew, so thanks for that.

 

14 minutes ago, cheesegas said:

Also - no problem having two inverters, as long as you don’t connect their outputs at any time, eg plug both into your 240v circuit.

 

I don't quite get you're saying here. If I go down the two inverter road, I'd be thinking of connecting both inverters to the 12v battery bank, and having the Sterling power the existing 240v circuit, and getting a small the laptop specific inverter, with a built-in three pin output, which would not be connected to the existing 240v circuit at all.

Link to comment
Share on other sites

1 minute ago, Col_T said:

@cheesegas

UPS stuff - that's interesting and not something I knew, so thanks for that.

 

 

I don't quite get you're saying here. If I go down the two inverter road, I'd be thinking of connecting both inverters to the 12v battery bank, and having the Sterling power the existing 240v circuit, and getting a small the laptop specific inverter, with a built-in three pin output, which would not be connected to the existing 240v circuit at all.

Yep that’s fine. I was checking to make sure you weren’t intending on connecting both inverters outputs to your 240v circuit at the same time, so you could use one or the other. Keeping it totally separate is perfect. 

Edited by cheesegas
Link to comment
Share on other sites

12 hours ago, Col_T said:

@cheesegas

UPS stuff - that's interesting and not something I knew, so thanks for that.

 

 

I don't quite get you're saying here. If I go down the two inverter road, I'd be thinking of connecting both inverters to the 12v battery bank, and having the Sterling power the existing 240v circuit, and getting a small the laptop specific inverter, with a built-in three pin output, which would not be connected to the existing 240v circuit at all.

 The outputs of the two inverters will be out of phase, so potentially 400 volts plus across them.

 

Locate than at least 2 metres apart so that you cannot physically touch both at the same time to eliminate the risk.

  • Greenie 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.