DC to AC Adapter to run my laptop?
 

I'd like to plug in a 110v adapter to run my laptop while traveling on business. Thinking about those that plug into the cigar lighter. Any damage potential to the car? I do have several computer batteries, but I need them when I arrive and not worn down. Trips are usually six or so hours.

The car is an '86 300sdl

Thanks..Rob

I have no problem doing it using a 12V extension cord with two outlets. There is not a lot of room in the ashtray for an inverter.

I've used 600 watt inverters with no problem to run computers, Ipods etc.

As long as the power draw from whatever you plug in ( plus the loss factor of the converter) does not exceed what the lighter socket is designed for you should have no problems... we used to run an inverter to operate the Homemedic massager for my father on long trips...

I just ordered a 1000watt inverter for the eurovan. Dunno that I'd trust those cig lighter ones, our cars were made when people used them for their specified design, lighting up cigs.

I hard-wired a 700W inverter directly to the battery. I fed the wiring through the firewall, and included an in-line fuse. Consider a set up like that if you don't want wires running all over your ashtray / center console. It all tucks neatly in the passenger footwell or underneath the passenger seat. No issues after 2 years...

The cigarette lighter is only able to carry at most 80W through the cigar lighter harness. My recommendation would be to hardwire it to the battery... I pulled out the seats to my car, and mounted it in one of the storage trays in the back. Used 4 gauge welding cable. I also bought a set of the terminals that are platinum coated, and cut off the old terminals. These are meant for stereo/multi amp installation, and I wired it and the amps through that...
I really like the cobra 800 watt inverter that is readily available from a good number of truck stops...

Great...To the Battery it is!
 

Thanks all. Good point on the Cigar lighter max capability. I wondered about that. I'll run some wire to the battery.

Rob

Be sure to fuse it at the battery, so you don't have a fire if it shorts somewhere. For my ham radio installs I usually use 10 ga. wire and a 30A blade fuse in an inline holder.

Watch the temperature of your charger, most inverters are modified-sine which is really more like a square-wave which is less efficient and can in some chargers get pretty hot.

I think you are wasting your time to fiddle with the wiring at the battery if you are only running a laptop. Check the fuse rating at the fuse box for the cigar lighter circuit. I do not have the FSM or car right now but I would expect it to be 20A+. That is 240W continuous which has enough juice to run the converter and your laptop. I check the power pack on my Dell computer and is only rated 90W. That is the max, running wattage would be less. My Dell is 3 year old. Modern day laptop would draw less, much less, power. So in short, your cigar light circuit would provide ample power.

Check the power pack of the laptop rating first before you mess with the battery wiring.

It is true that DC/AC inverter produces modified sine-wave but the power pack of any laptop is switch mode power supply SMPS and can take modified sine-wave without issues. The efficiency on switch mode power supply is much higher than linear power supply and generate less heat. Some SMPS turns itself off if there is no load.

what I read about DC wiring, you under rate wire size due to the current demand. in A/C current, there is a break in the phase as the ac cycles 60 times per second. DC of course does not do this. the current is continuous.
#10 is not capable of sustaining 30 amps of DC 12 volt current safely...
I'd use #6, and have a MAXI fuse for 125% the watts needed at 12V
if your inverter is rated at 450watts, the amps at 12v is 37.5 125% of that is 46.875 use a 50 amp fuse, and be sure the wire is rated to handle 60amps at 80C that's like #2 I think... perhaps it's not taking heat from the engine compartment into the equation... I'd at least use #6 for such a load.
this chart seems to think wire size is MUCH smaller than I do per load in DC use... http://www.offroaders.com/tech/12-volt-wire-gauge-amps.htm

most cig outlet fuses are either 8 amp or 10 amp.
I've not seen any rated above 10...
that'd be a max of maybe 120w...

I agree on the cig adapters for a laptop though.
most are only going to draw like 80 watts... most cig adapters are I think, 120 or 100 watts... plenty for all but the most robust laptops...
Hmmm.
my cheapo toshiba laptop has an input demand of 1.5amps... at 120v, that's 180watts... wow.
output is only 3.95a at 19v... that's only 75 watts, of USE... so, the cig 100watt adapter should be fine for mine...

I have a 75w inverter that plugs into the cigar lighter. It works just fine and is all that's really needed to power all but the most extreme laptops.

BTW, I repair computers for a living, but used to be a mechanic ;)