Power invertor and notebook in car 1

[Frankenherder]

OK, I have had nothing but bad luck with Power invertors. All I am looking for is to have my notebook running next to my while it is hooked up to my GPS running streets and trips.

I have been through 3 invertors and they just seem not to work. My 75 watt invertor now makes my notebook flicker like it is going to battery mode (Screen auto dims a bit) then brightens up back into 120 power mode.

Has anyone seen this before? is 75 Watts enough for a notebook?

Thanks
Matt

 

[attrofy]

I don't know what your particular notebook PSU amperage draw is, but to be safe, I would go with a 250-300 watt inverter - they aren't that expensive. At a minimum, I would reccomend a 175 watt. But that is just me. I would think a 75 watt would be a bit low.

Here is a brief rundown of how to size your wattage needs

http://www.4lots.com/index.asp?PageAction=Custom&ID=10

From the same site, here are two inverters that might be good starting points:

http://www.4lots.com/index.asp?PageAction=VIEWPROD&ProdID=154

http://www.4lots.com/browseproducts/Go-Power-300-Watt-Inverter.html

 

[Frankenherder]

Hmmm, just looked it up online, 65 watts. I probably do need a bigger invertor since the invertor only states the maximum and it seems pretty close.

I just liked that one since it was rather small.

Thanks for the info.

Matt

 

[kmcferrin]

It depends on your laptop, but you can probably get the wattage figures from the power supply of the laptop. I know that we have some laptops here at work that are clearly labelled 95W next to the power plug.

 

[attrofy]

I don't know if PSU wattage has to do with size of the inverter. But as a rule of thumb for inverters and UPS's I usually use the output wattage of the PSU as a rough rule of thumb. I believe this is wrong - as I think the PSU draws more wattage then it outputs - but I could be wrong. A quick look at an Antec 550 True Power PSU shows AC input of 115V/12A. My calculations say that is 1380 Watts. Rated output is only 550 watts - max. For arguments sake, that would require a 1500 watt inverter (with a little to spare for good margin).

However, a tower PSU is supplying specific voltages and amperages across multiple rails, so it is possible that a laptop PSU operates differently. The tower is showing over double the input required for the rated output. Just some food for thought. Maybe someone will chime in that knows more about this.

 

[Sympology]

Attrofy.

Your correct. No electrical device is even close to 100% efficient. So if the Laptop pulls say 90w, then expect the actual pull from the power source to be over 100w. It's the old physics rule, energy is never lost or created only converted. So if a PSU get warm, some of the electrical energy is being converted into thermal energy.

Wow, I'd did learn somehing in my Science courses after all....

Only the truly stupid believe they know everything.
Stu.. 2004

 

[Frankenherder]

OK, I just checked, turns out my Inverter is a 75W. The packaging says it is good for laptops (wrong!) My Dell Inspiron 6000 Draws 90 W, there is the problem.

Thanks guys!

Matt

 

[LawnBoy]

A star for Stu, it's good to see another electronics tech in the crowd.