Power inverter for laptop

[DLB]

I have an HP pavilion dv4-1145go laptop and I would like to use it in the car during a camping trip.  I read on-line that I should use a pure sine wave power inverter to convert dc to ac. I called my local electronics store and they told me that this filter is built in to the pc's ac adapter so I really do not need the pure sine wave inverter.  Do I need the pure sine wave power converter (least expensive is about $100)?  Also, how much wattage to I need to run this laptop?  How much is too much?  Thanks...

[Elwoodblues66]

Saw that no one else gave this an answer so thought I would chime in with my $.02

First off..  No, you don't need a sign wave inverter to run your notebook.  The power brick does a good job of taking the crappy AC power a inexpensive inverter puts out and converting it to DC for your notebook to use.  The power brick does act as a 'filter' as a result of this process.  But, without 'clean' power the brick does not run as efficiently and will get warmer as usual and might draw a bit more power. 

How much power do you need?   Sorry, didn't look up your notebooks specs. But, it is written in really small print on the power brick..  Short of breakout of the reading glasses..

180 Watts 20" screen

120 W 18" screen

90W 15-17 " screen

65W 12" screen

Don't know what the netbooks use, but should be between 45-65w

That said, you should take the wattage your notebook uses and double it when looking for a inexpensive inverter. Some only list peak power output which is half of continuously operating power. Others are over rated and will heat up, burn out and do other nasty things when run near the max continuous power output.

Also consider what else you might want to run at the same time when out camping..  Maybe a compact florescent bulb or 2? ( 15 w each ).. 

I picked up a Black & Decker 400W inverter from Home Depot last year and have had good luck with it. ( except for a noisy cooling fan ). I think the cost was about $40.. Considering it's operating environment ( construction in Arizona ) it has lasted far longer than I expected.

Another couple of things to pay attention to..  Is how much 12v a 400w inverter will draw. Near maximum sustained load it will draw in the neighborhood of 40 amps of 12v power ( rough & dirty math ). That is too much for  your cigarette lighter to provide. It does come with mini jumper cable style clamps to go directly to your battery.  Also keep an eye on how long you run it and the reserve time your car battery has. ( If I remember correctly ) most batteries will tell you how many min they can run a 20amp load and still have enough power to start your car. Exceed that time and you risk having to run around the campsite asking who has jumper cables. 

[DLB]

Hey, Elwood, Thanks so much for your reply, you just saved me some money!  I appreciate the time you took to answer my questions (and I was feeling a little rejected having no replies :-). 

I had not considered the possibility of drawing too many amps. I was only thinking of not messing up the laptop.  It has a 14" screen and uses 65 W.  According to your formula, I should only need a 130 W power inverter which would draw about 11 amps.  I'm not sure how that would  work with the cig lighter or adversely affect the truck's battery.  I was actually contemplating using the computer to run some road logs on DVD while my husband is driving.  It seems that it should help that the engine is running while the battery is being drained. 

I have seen on-line the power inverters with the little clips that hook directly to the battery, but that seems to be an awkward solution while the vehicle is moving.  Since we camp in some pretty remote places, having a dead battery would NOT be a good thing!  Thanks again!

[Elwoodblues66 · Accepted solution]

Glad I could help...

As I said I have been using inverters to provide power when on the job in construction and while camping for some time.  Have not been able to get out camping for a while but had developed a interesting setup for our favorite camping spot.

picture a small box canyon that the open end opens to a lake and is about 80 feet deep and 150 feet across.  We would string 1/4 inch nylon line across the top of the canyon and then use that to pull and support electrical 'zip' cord ( like a lamp cord ) across the canyon. On that zip line we placed lamp sockets.  These sockets are very similar to what are used at Christmas tree lots. They clamp onto the line and pierce the insulation to get to the electrical conductors without having to strip the insulation or cut the line. On these sockets we would place 14w compact florescent light bulbs and downward facing reflectors we got elsewhere.

So as you can see, the setup only drew about 60w but lit the whole area very very well and had the additional benefit of drawing the insects to the lights that were well above our heads.

It is just something to keep in mind for you..   Even 1 light pulled up into a tree can give general lighting for an area and keep people from stumbling in the dark and help draw insects away..

Yes, a 120w inverter will probably perform for you.  But in my experience inverters of less than 200w are made very cheaply. The few dollars you save will be spent again when this inverter dies before it really should.

My advice would be to get a 400w inverter like I described. Check the box to be sure it comes with the lighter adapter and the clips. You can use the lighter in the car where you will just run the notebook or DVD player and still be well under the 20a limit of that socket.

Most 'better' inverters have some method of protection for not draining the car battery down too far. The black & Decker one will make a noise, others might just shut down. When  you hear the adutiable alarm go and start the car right away. The alarms are not as accurate as we might hope and also depend on the condition of your battery ( how old it is ).

I know it sounds like I give a lot of warnings and a lot of different things to remember but don't worry. Once  you know the basic limitations of making your own power and keep them in mind you will be just fine.   Especial on the road to your destination.

One last thing.  I would advise you run to the auto parts store before you go and pick up a box of fuses. For the type your car uses to protect the lighter outlet and for the type the inverter uses inside the plug that goes into the lighter. Just unscrew the metal tip of the lighter plug to reveal that fuse and get some spares that are identical.

[DLB]

Thanks again, Elwood!  Your suggestions are great, and I'll keep them in mind for my trip.  The suggestion to get extra fuses is really good--something I wouldn't have thought of. ---D