What's the best method to power a laptop?

Delboy

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Is it to use a battery lead or via an inverter? Because as far as I understand the battery lead must have some sort of inverter in them, because the output voltage from my mains psu is 20v. And and an inverter is more usable in other situations, although there must be loses in the process.
 
Hi Delboy
If you go to maplin or any PC/office supply shop they will sell you a direct cable to run from your 12v outlet which will boost it up to the correct voltage for your Laptop, this will not waste too much current converting to 230 volts and back down to about 20v as an inverter would.
 
Some inverters are not as efficient as others

I have used all sorts of solutions to this problem. beware the cheap inverters from maplins. although it seem logical that because they are only taking 12v and jumping it up to your required voltage they do not always do this in an efficient manor. some better quality 240 inverters actually drain less power to do the same job.

I charge my batteries with a 200w solar panel so can see the power usage on my control panel.

my advice; Get a solar panel (Wind and Sun Ltd: Design, Supply and install wind and solar systems will advise on how big you will need) then attach it to a dedicated leisure battery that is wired to a dedicated good quality 240v invertor. the bonus to this is that you can run all sorts of things like blenders for example (i like smoothies) and your batteries will last for years. Its expensive but over the years will save you the cost of replacing batteries. i have been running the same leisure bats for nearly 6 years know.
 
PS

Forgot to say that most quality 240v invertor's only pull as much charge as they require for what you are running.
 
Well, in the mean time I've bought a sine wave inverter from Halfords, about £30. And I'm currently running it on an engine starter, cheapo from Argos, and had about 2 hours up to now. When the voltage drops low it powers down to leave enough power to start a car engine. Well that's what it says anyhow!
 
Thats cheap for a sine wave inverter :eek: usually they are the modified sine wave ones for about that sort of price.
 
We now have two Maplin 12volt laptop adapters, have used one for over 12 months its very good! multi voltage and phone chargers etc, the new one is for mains and 12volt, £45 the first one was £30. We have solar panels but found when we used the 800 watt inverter the power didn't last very long, the trouble with inverters is they take power just to run, the 12volt system is much better...jack
 
librarylife said:
Forgot to say that most quality 240v invertor's only pull as much charge as they require for what you are running.
Click to expand...

If only that were true!... my business lies in the servicing, maintenance and procurement of off-grid installations and I'd love to get my hands on 100% efficient inverters!

On large inverters, say 5000 W and above, one does see efficiencies as high as 96%, especially with grid-tie kit. BUT, you'll only get those efficiencies when the inverter is running near capacity, so the "lost" wattage is more than many people on this forum would regard as their total desired load. (100 to 200 Watt). Typically, even with well designed, high powered, inverters you'll be down in the 80% area, and a standing load of 20W or so, just to power the inverter circuit itself.

Then things get worse - that "lost" energy manifests itself in the form of heat, and we may need cooling fans to remove that heat from the electronics - guess where that extra energy comes from :)

The original question asked about a specific load - a laptop. The optimum answer depends on a number of variables - in particular - will the laptop be used in conjunction with other equipment that also requires a "mains" supply, external disk drive, scanner, printer for example?

Option 1: Use a "cigarette lighter" converter, for your particular laptop. Advantages: Pobably the most power efficient; it will be working at the load the circuits are optimised for. Disadvantages; how are you going to power any peripherals? You will probably be plugging into the engine starter battery, rather than the leisure circuit. You could take so much charge from the battery that you can't start the van up again.


Option 2: Use a 230V (+10%/-6% - don't get me going on "harmonisation!) inverter into which you plug the "mains adapter" that came with your laptop. I strongly suggest a true sine-wave device.

Advantages: You don't have to buy a "12v" accessory for your laptop. You can plug in other things that require mains voltage - toothbrush chargers, mobile phone chargers, computer peripherals, blenders, whatever - whilst you're using the laptop. Convenience - we're used to the ubiquitous "three pin socket" - it doesn't need so much thinking about. You can hard-wire an inverter into your van's system so that you have two 230V circuits available, one from the hookup (when you can) and another from the inverter. Needs a bit of intelligent use though so you don't plug the slow-cooker into the inverter circuit!

Disadvantages: This wastes power, and you don't have much to spare. Every device you plug into the inverter circuit that then has its own voltage converter wastes power. The inverter has its own power losses (see above). It's a single point of failure - if you've bought a cheap'n'nasty off fleabay and it dies on you - then you've lost all of your "mains" devices for the duration of your trip.

There is a third option - those with an elec. eng. background have probably worked it out for themselves - but admit it: it's not for general usage is it...? and will almost certainly void warranties if it goes wrong.

For these I have assumed that the engine is NOT running - the voltage spikes from an alternator are scary, and laptops are expensive. Your risk if you do!

Every person will have their own needs/wants/cash/stress/reliability matrix. If your requirements are "average" there's lots of ways you can cut it and get acceptable performance - as soon as you get specific then you can go very, very wrong.

Try and work out your requirements of the system, read as much as you can, ask people with proven experience (not those just cut'n'pasting something off the net that they haven't understood!), and install something you understand and can work/live with.

Mind the gap between expectation and reality!

Mild Red
 
Laptop charging

Depends on laptop size, we have a netbook as we found a 15" took too much power, but we use a 300watt invertor, hope this helps. jovik
 
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