why aren't mini USB monitors a widespread way to get laptop run longer on battery?

a big chunk of laptop energy consumption is the monitor. So, presumably, if we turn off the monitor (possibly via some Windows hack) and use a smaller USB monitor instead, we will spend less energy and hence the battery will last longer. Next step might be making the external monitor with keyboard and mouse pad built-in to maximize user convenience, sort of like a smartphone but in effect just a laptop terminal. Or maybe just find a way to attach the external monitor to the (turned off) laptop monitor and use the laptop keyboard and mouse pad as usual.

So what’s wrong with this picture? Since the above described technique does not show up in the “latest and hottest in the world of gadgets” type of news reports, is there something that I am missing here?

If you’re willing to carry around a big ol’ monitor, you probably won’t set it up anywhere that doesn’t have an outlet nearby. I don’t really see any reason to save battery at that point.

Also, I think notebook monitors are pretty efficient. I’d question your premise that one could save energy by using an external monitor.

I don’t think USB could deliver enough power to light a monitor of non-tiny size, anyway.

Yeah… a laptop with an external monitor, keyboard, and mouse may as well be a desktop.

First, if they could get an acceptable monitor to be low enough power to have a measurable effect on battery life alone, why wouldn’t they just build that kind of monitor into the laptop from the beginning?

Second, if you do it with USB you’ll be limited in terms of monitor size, monitor resolution, framerate, or all three compared to DVI (for example), because modern (2.0) USB hardware doesn’t ship bits as fast as dedicated video hardware does. USB 3.0 has been promised to be usable as a good video connection, and I don’t doubt it will be given that USB 2.0 is a somewhat poor one already, but we aren’t there yet.

I should add, USB-connected monitors exist already. Well, USB-to-VGA external video cards exist; I don’t know about monitors that have USB hardware built in. The (decidedly pro-USB) website I’m linking to has this to say, though:

That limited bandwidth works against any display device connected via USB 2.0. The review goes on to mention some choppiness in videos watched full-screen, but claims smaller sizes work well. Which is, of course, what one would expect when there’s a slow link in the chain to deal with.

The fan on my laptop doesn’t work, and on occasion to cut down on heating I’ve turned off the built-in monitor and used a VGA monitor. It does run cooler, and that means less power, but that’s for the laptop only. I don’t doubt that there’s no savings once you include the power for the external monitor.

If you have a laptop, and forgot your power cord, but there’s an external monitor nearby you can use, I do believe you’d get longer life with the laptop monitor turned off.

ugh! the signal (Derleth and ZenBeam) to noise (everybody else upthread) ratio in this thread is much lower than normal in my experience here.

Yes, of course I am aware of the mini USB monitors. That’s exactly why I started the thread - I am surprised that they are not being widely used the way I proposed in OP.

Power consumption of LCD monitor is proportional to its area and to (usually adjustable) brightness. So the less the area, the less the power consumption. When I read books or write notes or even do simple programming I don’t need a huge screen I am saddled with courtesy of the laptop manufacturer. A small, power-efficient monitor will do.

An easy way to observe the difference that monitor power consumption can make is to adjust the brightness and then look at the Windows prediction about remaining battery life. I have routinely seen a difference of one hour worth on a laptop with about 4 hours best case battery charge. That’s just on brightness, without the reduction of monitor area that is inherent in using the mini monitor.

Could you get the same effect by running a lower resolution and confining pixels on the screen to a smaller portion of said screen?
It would save lugging a second monitor.

I’d run the experiment myself, but I’m on an ASUS eee with a 10 inch screen. There’s no ‘smaller’ to go from here and actually be able to see the screen…

Because battery life isn’t that important to most people. Not to the point of using a smaller display or carrying an extra monitor.

Also, if you’re willing to carry an extra piece of hardware to prolong the battery life of your laptop, an external battery or a spare battery would be a more logical choice. That way you don’t need to sacrifice display area.

Besides, as soon as you add an external monitor, your computer is no longer a laptop. It’s a portable desktop that needs to be set up on a desk or table. How are you going to use a setup like that on an airplane or coffee shop?

So get a smaller laptop.

I can’t understand what you’re getting at. If you mean why don’t people use devices like Delreth linked to more often, it’s because they don’t need to. That device doesn’t have a screen, it just turns your USB port into a VGA port. You still need an external monitor that draws power from the wall, and if you have access to that, you can just use the laptop’s built in display port. That device simply lets you connect two or three external monitors to your laptop.

If, on the other hand, you mean a monitor that’s powered from the computer’s battery via the USB port, it’s simply not feasible, as was said repeatedly in the “upthread noise.” A USB port delivers 5V at 500 mA. That’s it. That’s enough to run a screen maybe a little bigger than an iPhone. While you might be fine with that, I suspect very few other people would be.

You can do something similar using the monitor settings itself. By setting the contrast, brightness, and resolution lower, you wouldn’t need to use a separate screen to do it, and you would achieve your goal of saving battery power.

On my 15" laptop, I get an additional 1 hour by using the lowest monitor settings.

why should noise be limited just to upthread, eh, Silophant? Your valuable contribution to the downthread one is much appreciated.

Here http://www.google.com/products/catalog?hl=en&biw=683&bih=403&q=usb+mini+monitor&um=1&ie=UTF-8&cid=3054258952435807248&sa=X&ei=zj59TY-POs6BtgeqkrS6BQ&ved=0CDcQ8wIwAA# is a $110 USB mini monitor that is explicitly advertised as:

And here is an apparently similar device for $80 http://www.google.com/products/catalog?q=mini+usb+monitor&um=1&ie=UTF-8&cid=14588828931883720482&sa=X&ei=IT99TbPAF9K3twf4zay6BQ&ved=0CIgBEPMCMAE#

So, yes, it’s not just feasible but already on the shelves, so to speak. Now, admittedly, their attachment of the “stand” to the monitor is not a nice thing for portable laptop purposes, but maybe the stand can be removed. Or broken off. Or maybe the OEM could see the light and just produce the gadget without it in the first place.

I purchased my laptop as a compromise between the screen size I want (21" diagonal or larger) and the size portable device I want to lug around (no larger or heavier than a postage stamp). I suspect all other laptop buyers make the same tradeoff, although each buyer’s individual answer may vary. For me this time the compromise came in at 11"

I cannot see how carrying two monitors, the large built-in one and the small external one will ever be a popular option. It reduces my screen reading utility (bad), while decreasing my portability utility (aalso bad).

Whether or not such a device is technically feasible is immaterial. It fails the basic “why would anyone want such a thing?” test.
On the engineering feasibility side you’d have to ask if the marginal weight of the second small monitor is more or less than the weight of the battery you could leave out because of longer monitor life. Surely no one would carry a second monitor if the total combination not only was more peices than the baseline laptop, but also weighed more and/or had less battery life. There’s gotta be a gain in some category before it passes the laugh test, much less suceeds in the actual market.

But you’d also need to factor in what percentage of use would be on the main versus small external monitor.

e.g. if we assume 100% utilization of the small monitor and it weighs 1 lb, then as long as we can cut out >1 lb of battery & still have the same life the thing *might *be saleable vs the unmodified single-monitor laptop.

If we assume 50% utilization of the small monitor, then we can only leave out half as much battery to still get full baseline lifetime out of the laptop. Which means our external monitor must be very small and light.

Given the extreme convenience of the single piece clamshell or tablet design, vs fiddling with multiple units & cables, I’d bet actual use of a smaller external monitor for typical laptop tasks might be down around 5-10%. In other words, the monitor would have to displace 10-20x it’s weight in battery to make the whole system a collective winner. That’s not an engineering possibility today.
So the whole thing is a double fail: you can’t build it, and even if by magic you did, then (almost) nobody would buy it.

IMO, your mileage may vary.


could you please elaborate on the percentage of utilization bit? I sorta don’t get it. If I am going off on a plane ride and use the small monitor instead of big one to keep the battery running longer, what’s that magical percentage going to be?

Like I already said above, the gadget physically exists and available for sale. I am not being hypothetical here.

I agree with your point about extra batteries. If an extra battery of similar size and cost can deliver bigger benefit, that might make more sense. Except possibly for an additional factor of amortization - batteries degrade from use whereas monitors not so much. And monitors can be used across laptops while batteries cannot be (except for the universal external batteries).

Only if you had an LED monitor, which is rare enough these days it isn’t even worth thinking much about yet.

On an LCD, and someone should correct me if I’m wrong, the main power draw is the backlight, which is a single lit panel that’s always on at some constant brightness as long as the monitor is on. Using less of your monitor or going to a lower resolution doesn’t affect how bright the backlight is, so it wouldn’t have a noticeable effect on how much power your screen draws. As mentioned above, going to a dimmer setting or reducing contrast both help, and I’m fairly sure going dimmer helps more.

What I was getting at was your gadget has to earn its way into my knapsack.

My overall point of view was A) assume the customer wants a certain fixed battery life and then B) determine how we could trade off carrying less battery and an additional smaller less power-hungry monitor to stretch the smaller battery capacity to the same lifetime. In that formulation of the problem, the weight of the monitor must be fully paid for by reduced battery capacity requirements.

If I use the aux monitor for every single minute I use my laptop, then I have one tradeoff case to consider.

But if I only use this gadget maybe 10% of the time I use my laptop, then 90% of the time it’s just useless weight in my knapsack. And *if *most of the time it’s just ballast, it better be pretty light ballast itself, or have massively less power consumption than the main monitor.

In other words, how willing I am to carry it around depends not only on how bulky / heavy it is, but how much I use it.
I am not suggesting that small external monitors don’t exist. What I’m suggesting is that ones which provide a net benefit versus battery life as described above don’t exist. Because they don’t come as an integrated system with the laptop & its battery. And if they did, the state of the art today is still that the extra weight & bulk of the monitor is much bigger than the amount by which the battery can be reduced. Even at 100% aux monitor untilization. Ansd as re-described above, the less the aux monitor gets used, the worse the terms of the tradeoff become.
As to your last point about useful lifetime of monitors vs. batteries …

The world’s landfills & 3rd world recycling centers are full of electronics which are functional but obsolete. A device is “useful” only as long as it provides value to its owner according to the owner’s definition of “useful”. Whether or not it still works as well as the day it left the factory is utterly immaterial.

I predict about a million original IPads will find their way into landfills in the next 6 months as their owners declare them totally useless compared to the IPad2 they really want now. The fact the old ones work fine just doesn’t matter.

By that definition, you’ll find your mini external monitors become non-useful as fast, or faster, than the batteries lose their ability to hold a charge. My previous now 3 year old laptop is useless to me; too slow & heavy & too small a disk. But it’s factory battery will still hold a charge just fine. Today’s bleeding edge flat panel displays will look like trash compared to what we’ll have in 3 years too.

There are industries where equipment’s economic life is long, progess is slow, and time to wear out is relevant as a measure of economic lifetime. But digital electronics is not one of those industries, nor has it been since the 1960s.

Those USB monitors appear to require drivers. Do they even work like conventional monitors? I.e., could you see anything if you powered on some random machine with this thing plugged into the USB? It doesn’t seem to be the case, to me. So that would further limit its general usefulness as a low power screen alternative, IMO …

This is the most ridiculous statement I’ve read here for a while.
Sure, there are lots of iPad 1 owners who will upgrade (my Wife is really Jonesing for one), but all those old iPads are going to be given to other people, traded in, or sold on ebay. To think that they will be just thrown away is well, stupid.