Hi, my kids are wanting to be able to play on their laptop while I am driving on long trips in the car. I was wondering if this power inverter would be safe to use from my cigarete lighter. My laptop uses 130 Watts at the very maximum load, which is very rare, and this inverter is rated at 150 watts so that seems ok. I was just wondering if my van can supply that much wattage through a cigarette lighter. The inverter I have in mind is this one. TrippLite PowerVerter Ultra-Compact Inverter with 1 AC Outlet : Computer Accessories | Dell,

 

That's cutting it pretty close? Just from back of the envelope calcs. Figure 10 amp draw.

 

Where did you get the 10 amps from? Is that how many amps the cigarette lighter can output.

 

Well I'm not sure, remember a cigar lighter might be around 10 amps, but isn't continuous load. Just for a few seconds.

A laptop run by inverter will be a continuous load, whatever it might be. Around 9 or 10 amps if your figures are correct. And there needs to be a little overhead built in too, the inverter and the circuits aren't run at their design limits.

 

FWIW I ran a 400 watt sustained and 800 watt peak inverter in my little Acura Integra a LOT - like hours at a time without issue in the stock cig lighter.

I cannot imagine there would be any trouble with your proposal.

 

You didn't tell us what year your van is, so I made a guess and pulled the Owner's Guide for a 2009 E-350.

There are three fuses for the power outlets, one for each. Each circuit is 20A, which is 240W. Assuming you have a ridiculously inefficient inverter that is only 80% efficient you have plenty of overhead to safely use the inverter.

I pulled the specs on my wife's Odyssey a few months ago, and that thing has 15A circuits for the power outlets. I've never seen one limited to 10A.

 

Remember that the inverter is only drawing the power that you're using. Plug in a 400W load and you will blow a fuse in seconds.

 

If the only thing you're going to run is the laptop, that inverter might do the job, but a better solution is to order the correct car charger for the laptop.

Assuming one is available, it will be much more efficient.

Go to ebay or amazon and type in 'laptop car charger _______'

Fill in the blank with your laptop name and model number....see what pops up.

 

Ah, I should have dug deeper. A 20A circuit should have plenty of capacity.

Laptops generate a lot of RFI hash, anybody ever notice any problems with the vehicle electronics?

 

Correct. I would never expect to hook up 400 watts of gear on that one circuit!
I had just be mostly running a USB 5W draw for hours on that thing.

 

I am curious as to what kind of laptop would suck that much power--that is almost desktop tower kind of juice. My Lenovos have 65 or 90 watt power supplies but seem to draw about 25-30 watts at most when the battery is charging...

If you have a 17" screen gaming laptop it might use a fair amount of power, but the laptop battery should buffer the power needs during any surges in usage. Most laptop CPU's max out at about 35 watts (some are less) and drives and screens should be only 5 watts or so at most. (I remember circa 2005 buying and returning a Toshiba that had a full 90 watt desktop Pentium chip--that would suck down its battery in about 45 minutes and was a stupid loss leader machine.)

We have used a 100 watt inverter in our van for years to charge laptops, video camera batteries, etc. I think you will be fine.

George

 

My last laptop was a 17" unit with an i7 processor. That thing produced a LOT of heat and came with a 130w power adapter. It was replaced with a Surface Pro 3 that draws a minuscule 36w.

I've measured power consumption with a Kill-a-Watt device before, and I've never seen one act that way. I believe they are programmed to keep the battery topped off when plugged into AC power, and I don't think they draw from the battery until power draw exceeds the capability o the AC adapter. Just a WAG based on the couple times I've measured it.

 

I think you are right about running off of AC when plugged in, Tom, but the battery is there if the power is not adequate (for instance if the same laptop was plugged into a 65 watt power supply).

Actually, the max power draw of a laptop would be if it was running full on (which I still think would not use more than 75 watts--even the hot i7 chips are supposed to have an operating wattage of 35 watts but a hot video card could use that same amount of power) AND charging a dead battery at the same time. I could see that situation using 100+ watts. I used to have a little utility program that constantly measured charging rate and it seemed to never go over about 30 watts but I don't have gaming laptops.

Power draw would be less if you got into the van with a fully charged battery on the laptop...

George

 

I'd go this route.

 

I'll chime in here. I have spent many thousands of hours running laptops in vehicles. It's often been part of my job, and sometimes varying from a large part to a majority of my job. Actually, without taking the time to actually do a rough calculation, I'd say it might be tens of thousands. No, I'm not exaggerating. I have run as many as 8 at a time, in a vehicle with a permanently installed inverter. I've also run them with the standard low power inverters we're talking about here, though not 8 at a time!



This is the best approach! The only thing wrong with it is that vehicular chargers are not available for every make and model. If you can go this route, do it.



Nope. Not going to happen. Fuggedaboudit. If I can't cause a problem with 8 laptops all running heavy loads and simultaneously connected to cellphones making calls and generating radio signals, you don't have any thing to worry about.


I've seen quite a few laptops with 140 or even 160 watt power supplies. Not your average consumer laptop, but business models can run that high.


Depends how long you want to run it. For cross country trips, a 100 watt inverter is not going to get the job done. Around town? Probably just fine.

But it won't last long. Even a good name brand like Tripp is not going to last if it's run close to its rated power.

Working for Intel for a couple of years, we had test some vehicles with 3000 watt inverters to power our laptops. They typically ran 2-4 laptops at a time. Occasionally 6 to 8. The math said we were fine. In fact, the math said we had massive overkill. These were professionally installed, and it was very high quality work, wired directly to the battery. Really nice work.

We ran them probably 4-6 hours a day, 5 days a week normally.

They lasted about 9 months and died. We went to 4500 watts and had no more problems.

Run it hard and you WILL need a bigger inverter than the math says you will, if you want to get any life out of it.


No, the charger circuit is not "programmed" to do anything. It's really pretty simple. If the available current from the charger exceeds the demands of the laptop, charging will occur. If the available current from the charger is less than the demands of the laptop, the battery will be drawn down.

How well a given inverter keeps up will depend on how long and how hard you run the laptop.

Just understand that the math really doesn't work for continuous use.