I had an after market empower adapter for one of my Dell computers did just that. Only supplies the power but does not charge the battery. Even plugging it into a regualr wall outlet. I called the manufacturer and was told Dell designed their computer only allows charging the battery when using a genuine Dell charger. I got a Dell charger and it worked.

Is that on all planes, or do the 772s have a higher limit than the 737s?

Last time, (again, this was a 772 and not a 737), I had my computer plugged in and was charging as well. That being said, my laptop is a netbook, which, using tlawrence85's formula, is only 30.02W.

I had this problem with a beefier Dell a while back on another airline, so it's not CO specific.

Ultimately I found that the power cut-off varied a decent amount between seats, so I ended up plugging into a different socket which worked better, cutting out only occasionally and resetting relatively quickly.

I would give them the benefit of the doubt and assume that 80W+ laptops were not something they anticated when they installed the power systems way back when...

Remember that if you're on the 772 in BF, you also have the USB port, which can be used for devices than can be charged that way (e.g., iPod, etc.). Won't help with the laptop, of course.

Way back when?

My 2007 model macbook pro is on an 85W charger.

It ain't your living room. There's limited 115VAC 60Hz generating capacity (most aircraft equipment is 115VAC 400Hz, 28VDC, or 270VDC) on the aircraft and higher power delivery to each seat would require larger wires, which means more weight. Same reason there's 2 outlets per row instead of 3. Is it worth the extra 50 pounds (WAG) of wiring to provide 140W/seat instead of 70W?

Most road warriors are carrying smaller (~12-14") laptops with 45-65W power supplies. The leisure travelers have and are moving toward low power devices (netbooks, iPads, iPods). I can see how it doesn't make sense to take the weight penalty to support the few guys with portable desktops or who have chosen larger power adapters (for quicker battery charging).

A problem charging an iPhone (which can't draw much more than 5-10W) is a defect. The 90W laptop is out of scope.

ITYM 30 watts, likely at 19V on the DC side.

Solution: Power Block designed for use on aircraft
 

Laptop manufacturers offer power blocks/transformers that are made for aircraft. I have one from HP. It has a switch on it that allows it to 1) supply power to the laptop and charge the battery or 2) supply power to the laptop only.

I've never had a problem since purchasing this and previously I had the same problems outlined in this thread.

Often I have to jiggle the plug before it sits just right and lets me charge my 15" MacBook Pro. It's not a very secure outlet. It will also often turn off once my computer is fully charged, and I'll have to plug it in again. So it's finicky.

I imagine a big part of it is the low current limit. A difference of 15 or 25W doesn't seem like a lot for a single outlet, but multiply that by four outlets per row and 20-30 rows, and you can see why CO is trying to ration us. My guess is also that the AC/DC converter is at the seat since running high voltage wires throughout the plane would be a bigger risk. Having used such converters before in other situations with higher current output, I can tell you they are unreliable at best and create a large amount of excess heat. I'm thankful that CO has them at all.

Difference between PWR on 737 and 777
 

I'm one of those guys that runs a powerful laptop for engineering work. I can attest that I've never gotten it to work on any 737 no matter how it is plugged in or from one seat to another.

I run the factory supplied 135W adapter (Thinkpad W510), it never works, it'll trip it every time on a 737. On a 777, it works just fine. And no I can't use a smaller power supply, if I use a lower wattage adapter, BIOS will slow the machine down to being just plain unusable. Its no fun carrying around a 2lb brick...

So I always go on with a full battery, low brightness and I'll get about 90 minutes before I have to go to watching the History channel........

As a point of reference, with a previous machine that only pulled 90W, it was hit and miss on 737s, usually hit (Thinkpad W500).

Flew Co 1776, IAH-PHL, and used the power outlet with my Dell E6400 without any problem. Loved the DIRECTV also.

I am running a Dell M4600 Precision Mobile Workstation with 180W power adapter. The simple act of plugging in the power transformer (without the laptop even connected to the other end) made the green light go off. So, it doesn't matter if I pull out my battery. I guess that the transformer running in idle alone draws too much power.

Good lord 'n' butter! What the bleedin' heck does your laptop do that requires a 180W power adapter? I mean... sure, "Mobile Workstation", but does it have a toaster? :)