well so i finally got my hands on a powertuner... got it today ran to walmart to pick up a power inverter i got the black and decker 400watt my laptop power supply is like 180 so i think im fine. i go out side and get ready hook everything up and i get a red light for a bad output... so i think my power supply is shot. so anyway i continue what i had planed and run to another store that my friend need to go to, while i stay in the car. i decided to mess with it one more time i get to work this time i turn the pc on and it fails on me again, cant get it to work again, so now im thinking its the inverter. go back to walmart and swap them with the same kind.. it does the same thing. so now im leading to believe again its the power supply. so i get home do what i have to plug the laptop in and it works at home. go outside to the car and with the car off it seems like it has no issue powering the power supply but when i turn the key over it messes up.. im confused on what the issue can be any one have any insight or a better inverter i can use?

the problem is your 400 watt black and decker is the PEAK output, what is the normal? I have used a 350w power inverter many times without issue.

Most plug-in power inverters will fail while you're starting the car.

Jaybur is right though... you should be OK with one that is at least 200W continuous duty.

Try completely charging your battery at home first, then turning it on after its hooked into the inverter. If the laptop tries to charge while connected to the inverter, it probably overloads it.

the reason they fail while starting the car is because with the key in the "start" position very few things are actually getting power, the cig lighter is not getting power in that position.

once the car is started it should come back on though.

my inverter is a 350w normal, but 700 peak. it is just a cheapy I bought 3 years ago, but it still works great.

but if ours is a 400w peak (they tend to advertise the peak, to get you to buy it). then I doubt it has a high enough normal output to keep your laptop charger happy.

this is the one i have

http://blackanddecker.com/productguide/product-details.aspx?productid=17928&toolview=4#details

i have tried with the car running and it still occurred. then i tried with the car off and in the on position same.

got in the car today to head to work and while driving i plugged the inverter in and it was fine turned it off and on still good unplugged the power supply for the laptop and plugged it back in, still working good. even was able to turn the car off and it was still running fine. went to turn the car on and it messed up turned the inverter off then back on same thing. then turned the car off still wouldnt come back on...

it seems to work fine off the battery of the car. would i be able wire the inverter to the power drop? what gauge wire should i get?

cant win for losing, can you Alex? I would say probably 12 or 10 AWG.

yea tell me about it haha, im soo close but yet so far away. and what really sucks is that its cold snowing and ill be trying to do this wiring with no cover or garage oh and one other thing no light.

The cigarette lighter plug is a direct to fuse and then battery supply, it is not interrupted by the ignition switch at all. The power supply may drop to 10v when starting though, but I doubt this would cause the issues you are describing.

Im thinking your cig lighter plug is corroded or vibration is causing intermittent connection there. hardwiring will eliminate your problem.