When I use my laptop in my Element, I usually use a 150 watt power inverter so I can have constant power and don't have to switch out batteries every 3 or so hours. When I plug the headphone jack into the aux in to get the sound throught the speakers and also have the power inverter plugged up (front or back cig lighter outlet), the sound coming through the speakers sounds horrible. Is there a way around this? Can I hardwire the power somehow and would that fix it? Thanks for any input.

Inverters don't produce the nice, clean sine wave that you get out of the wall. The best you can hope for is a stepped square wave, and more likely you're just getting a pulsed square wave (cheap inverters). Those create a huge amount of noise in the power supply, and that noise runs all through the computer. In fact, it's possible to burn out the power supply inside your laptop. (I cooked a laptop that way - it won't charge batteries any more.)

Besides, you've got 12 DC volts in the car, going to an inverter that converts it to (approximately) 120 volts AC, which goes into your power supply that converts it back to 12 volts DC or similar. What's wrong with this picture?

Ditch the inverter. Go looking for a cigarette lighter power adapter that fits your laptop. It will solve your problem.

That's great advice ReedPC. I always tell people to avoid inverters if possible for exactly the reasons you describe. It's voodoo IMHO.

I've had good luck so far with this model:

http://www.compgeeks.com/details.asp?invtid=SDR-70W

Note that the voltage is switchable, and the plugs are adaptaplugs. Therefore I give you two warnings:

1) Once you set the voltage for your laptop using the switch on the front, wrap it in tape a few times to keep the switch in place, as sending overvoltage to the laptop is very bad. You might even want to remove the slide from the switch as well.

2) Once you place the adaptaplug (if none of the five fit your laptop, you may have to go to radio shack to find one that's compatible, for another $2-$5) in the correct polarity, also tape it down. I even used a pocket clip ring from a ball point pen and a zip tie to secure it. Why? If the plug falls out and you put it back on the cable backwards, you'll be reversing the polarity of the plug you put into the laptop. That's really bad.

But for <$20, my thinkpad t21 has been super happy with it. When my A/C adapter died, I ended up using the adapterw with my workbench 13.8V 10A ham radio power supply to run my work laptop for about 4 months straight.

-brendan

One more thing: in addition to the "hash" produced from the laptop power supply, you may have also had a ground loop problem. There are in-circuit RCA<->RCA adapters for blocking this. Search the forums for ground loop, etc. One day, someone might even come up with a 1/8" to 1/8" ground loop blocker cable. :)

-brendan

Thanks for the great info. I was told with the inverter to unplug it a couple hours before I reached my destination so the car battery wouldn't be dead from running it the whole time....is this true for the adapter you posted above also? I have a T22, which settings am I gonna use?

[quote:361b4573b5=" "]Thanks for the great info. I was told with the inverter to unplug it a couple hours before I reached my destination so the car battery wouldn't be dead from running it the whole time....is this true for the adapter you posted above also? I have a T22, which settings am I gonna use?[/quote:361b4573b5]

The current (amperage) pull for a laptop will have no significant effect on the ability of your alternator to charge your car battery. Don't worry about unplugging it when the car is running (just don't use it personally if you're the one driving!).

Your laptop or your power supply should indicate what voltage it produces as well as the plug polarity. For example, some of the tiny print on the little brick for my T21 says:

Output: 16V 4.5A + ---*)--- -

So, I'd want 16V or thereabouts. And the 2nd part (badly indicated here, but as close as I could get it to the typical drawing for polarity) indicates that the plug should be set for center positive (or tip positive) and shield negative. That is, the inside of the connector is positive and the outside is negative. It's likely that the plug will have the word tip on it, which you will line up with a + sign on the cable.

Almost everything is positive tip these days (for a reason), but always check to be sure.

-brendan

I have been doing some testing with a laptop that I plan to use as my in car computer.
One thing I noticed as far as the audio quality is if you are running a line from the headphone jack there seems to be no way to reduce the line noise to zero.
What I am planning to do is use a USB audio device to create a level line out from my laptop. I already tested it and it sounds as clear as the line out from my MP3 player.
The one I am using (that I happened to already have) is the "iMic USB Audio Interface". You can get it from the Apple store.

Probably this is something you've already got covered, Kovert, but be sure to use an audio patch cable that has an RF choke on at least one end. There was a dramatic reduction in the noise and improvement in volume level when I switched to a cable with chokes on both ends and better than average shielding:

http://2dolphins.com/images/element/audiocable1.jpg

That is a very good point.
That looks like the exact cable I am using by the way :)
I have not tried it using a cable without the choke. I would say that the audio from the laptop headphones jack was not bad with the decent cable. But it was not as good as the level line out from my mp3 player.
Since the laptop will be my main source of audio I decided to go with the line out usb converter.