Is there any way to use a 200 watt adapter with a 75 watt plane outlet?
July 11, 2018 6:40 AM   Subscribe

I have a 200 watt laptop adapter. I'm going to be on a plane with a power socket that allows 75 watts out. Is there any way to make this work? What about using an external battery?

I'm going to Japan! Woohoo! The flight is 14 hours. Boo. My laptop has juice for maybe 2-3 hours if I'm doing anything other than looking at text with battery saver on and the screen dimmed. The power adapter is 200 watts. The standard power outlet on a Boeing 777-300 supplies 75 watts. I remember when I had a similar adapter for my last laptop that the outlet immediately stopped providing power when I plugged it in.

Am I doomed to flip whatever circuit breaker is in the plane, or is there some way to slowly charge my computer while in flight? Will it make a difference if I have the computer completely shut down and just plugged in when I try to charge? If I buy an external laptop battery, given that they all seem to supply between 68 and 100 watts, will my computer be able to draw power from it, or am I looking at the same situation, where the adapter will try to suck a watermelon through a straw?
posted by Hactar to Technology (9 answers total)
Buy an adapter that's 75W that's compatible with your laptop, and it'll be fine. Your laptop may pop up an alert saying it'll charge slowly, but as long as it's supplying the correct voltage (and it will be), it'll be absolutely fine.
posted by ambrosen at 7:37 AM on July 11, 2018 [1 favorite]

What brand and model of laptop do you have?

The more important question is whether or not your laptop will accept a 75W or less power adapter. I deal with a lot of Dell laptops these days at my work which come with either 90W or 130W adapters. When you switch to a lower-rated Dell adapter, it goes into a "low-power mode" which cuts the CPU power significantly (enough to make programs crawl). With the Dells, you can charge the laptop while power is off on a low-power adapter.
posted by Mister Fabulous at 8:56 AM on July 11, 2018 [1 favorite]

ambrosen has it, although I'd probably just charge it with the power off. It will be slow.
posted by aspersioncast at 9:58 AM on July 11, 2018

In your shoes, I can't help but wonder if it'd be cheaper/easier to buy a cheap Android tablet (Kindle Fire or whatever) and use that for the flight. Granted, this assumes you're planning to use it for media consumption only.
posted by Aleyn at 1:37 PM on July 11, 2018

The wattage on laptop chargers is the output wattage, not the input. Chargers are not 100% efficient, i was going to recommend a 65W one, to be safe. HOWEVER looking at the dell one on my desk its 120V 1.6A input, for 19.5V 3.3A output. Calculating wattage looks like 192W in for 65W out if i did it right, which would be way over the limit for the airplane (at max rating).

Something seems off with my math though, because this adapter is supposed to be 86% efficient according to the regulatory markings on it and my math shows like 30%.

Dell doesn't seem to have the input power specs on their site.
posted by TheAdamist at 1:43 PM on July 11, 2018

So I looked at your history, and I'm assuming that you still have the ASUS ROG g751jy from this Ask.

Operating under that assumption, I would suggest that you not try to run your laptop from the adapter while on the plane. Because your laptop doesn't have integrated graphics, it requires signifigantly more power than most while it is on and the plane can't provide it. Further, I wouldn't bother to buy a lower power adapter either. It probably isn't going to work, and if it damages your battery then your laptop probably won't work at all until you replace the battery. So, turning off to charge using the original adapter is the best you can probably do, if you really want to use your laptop in-flight. Unfortunately, any external power bank that might even be beefy enough to charge it is going to be expensive, you'd still have to turn the laptop off, and it might not be allowed on an airplane anyway.

So if you are willing to spend the money for an external battery, may I suggest buying an inexpensive tablet or even a chromebook for your travel entertainment/light work instead?
posted by monopas at 1:44 PM on July 11, 2018 [3 favorites]

Following on monopas's post, and to put the numbers in perspective, here is an article discussing the power draw of the Asus ROG G751JY, among other things. They write:
Our wattmeter recorded the ASUS G751JY using an average of 183 watts during our 3D stress test. (emphasis mine)
To compare it, my EliteBook 840 G2, while nowhere near as powerful a computer as your ROG G751JY, in a different stress test on a different website averaged 28.7 watts.

The takeaway is that the ROG laptop is a powerful, power-hungry beast.
posted by glonous keming at 8:27 PM on July 11, 2018 [1 favorite]

I don't have the ROG anymore, that died due to the fan crapping out and me not noticing. I'm on an eluktronics machine now. Roughly the same specs as a modern ROG except smaller and lighter. On the other hand, yeah, no integrated graphics as monopas points out.

My takeaway from this all is have my computer around for roughly two hours, and have my kindle charged and full of books. I can play video games while I wait for the jet lag to go away once I get there.

Thanks everyone.
posted by Hactar at 12:34 AM on July 12, 2018

(also, we're trying not to bring even more stuff with us to Japan- I'm only going to be there for 9 months and my wife for 12-16 and our space in Kyoto is going to be even smaller than our apartment in New York.)
posted by Hactar at 12:36 AM on July 12, 2018

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