# Inverter size



## Waleem (Nov 1, 2006)

Hi All

We have a 150W inverter in the van that we use to charge mobiles etc. It wont recharge my Wife's laptop though. What kind of wattage do you think we need for this task? (It won't be powering the computer, just charging it.)

Many thanks!


----------



## geraldandannie (Jun 4, 2006)

Waleem said:


> What kind of wattage do you think we need for this task? (It won't be powering the computer, just charging it.)


Hi John

That's a bit surprising. You need to look at the rating of the power supply (usually on a sticker) which will give its output ratings. This is usually the maximum required power. In addition, the laptop itself should have a power rating on it, which will be the power it actually requires to run, which shouldn't be that much more than the charging power.

Gerald


----------



## RichardnGill (Aug 31, 2006)

Our 150w inverter charges our laptop no problems.

It migh be a compatibility problems with the inverter, if poss try a different make.

Richard...


----------



## vicdicdoc (May 14, 2005)

Could it be anything to do with the inverter 'sine wave' ? [thats the limit of my knowledge . . you need an expert to answer it - where's DAB or ??


----------



## gaspode (May 9, 2005)

You're becoming quite a techie these days Vic, full marks. :lol:

A domestic AC supply from the mains will indeed be in the form of a sine wave with a maximum voltage of around +315 volts and a minimum voltage of around -315 volts which will give a RMS (root mean squared) of about 240 volts. Here's a diagram of a sine wave, you'll see that the voltage changes in a nice steady path.









A normal DC to AC inverter however produces a square waveform like this:










As can be seen, it's really a switched output rather than a smooth transition.
Now some battery chargers don't like this square waveform and refuse to work correctly. This is most likely the cause of the problem here. Getting a larger inverter is unlikely to solve the problem, buying a "pure sine wave" inverter would work OK but these are much more expensive than the usual square waveform type.

Best solution would be to get a DC to DC converter specially for the laptop, these are available from places like Maplins for around £20.


----------



## DABurleigh (May 9, 2005)

"Where's DAB"

I'm in Guernsey, Vic 

The other possibility is that the inverter is connected to the battery through inadequate van wiring. If this is the case, see if it works when the inverter is connected DIRECTLY to a charged battery.

Dave


----------



## 107850 (Oct 23, 2007)

Waleem said:


> Hi All
> 
> We have a 150W inverter in the van that we use to charge mobiles etc. It wont recharge my Wife's laptop though.
> 
> ...


----------



## AberdeenAngus (Jul 26, 2008)

Is it just the 1's that use power or is the 0's too ?


----------



## Waleem (Nov 1, 2006)

Thanks guys-food for thought.
The inverter wiring is fine-I know, I virtually rewired the leisure circuits when we got it and the inverter is wired directly to one of the batteries.
A little confused though-I understand the different inverter types, but then Fangio solved the problem he had just by increasing the wattage-which seems to go against Kens answer....... :?


----------



## DABurleigh (May 9, 2005)

Then look on wife's laptop power supply and let us know the numbers 

Dave


----------



## Waleem (Nov 1, 2006)

Okey dokey, here goes...

Input: 100-240V 50-60Hz 1.7A
Output: 20V- 3.25A


----------



## DABurleigh (May 9, 2005)

Then 150w has adequate punch, so regrettably it is the modified sine-wave bit that is buggering things up. With most laptops it isn't a problem.

Dave


----------



## Waleem (Nov 1, 2006)

Thanks Dave. I will pursue the 12V adaptor route then....


----------



## inkey-2008 (May 24, 2008)

*inverter problems*

we had the same problem, the inverter was not man enough for the job. as a rough guide to work out amps to watts multyply the amps by 220 . also if you dont let the laptop battery run down it does not draw so much power from the inverter. ours use to chirp if the draw was to great. maplins have some good deals on 650w inverters, andy


----------

