question about laptops.

[Mystic Muse]

I've seen some laptops with less than two hours of battery life and others with about 7 hours. My questions is do laptops with longer battery lives use less energy? I wouldn't think so but if it is then I want to get a laptop with a better battery life soon. I don't think my current one even lasts half an hour.

[golentan]

It's one way of extending the battery life, and is being used more often now. Look at how much of it is flash memory, for example. Without the need to spin a drive it tends to be cheaper. Macs are more energy efficient as a whole but are more expensive, and running linux actually reduces power consumption on a PC (windows keeps accessing things on the hard drive, so it has to keep spinning it up), LCD screens are far better. Most laptops will have information on their power consumption available if you look for it. Look for something listed as 15 watts or so. You can maybe find even better nowadays.

Longer life does tend to imply better power consumption, batteries are getting fairly standardized. A 7 hour lifespan will usually be a 15 watt computer with the same battery as a 45 watt with a life of 2 - 3 hours. So I would look there first as a good indicator, but look for those features above and do ask after consumption.

[KuReshtin]

The laptops that have a very long battery life has that is because of a combination of better power management technology (better energy efficiency) and bigger (higher capacity) batteries.

If you're getting a laptop from a bigger company, make sure that you know what size of battery you get with each model, since that can differ from model to model even if the actual machine type is the same.

For instance, if you look at a Lenovo R400, they will probably be advertised as having a battery life up to 6 or 7 hours, but that's for models that are more expensive and has the biggest battery available (9 battery cells in the battery assembly) whereas the cheaper models of the R400 laptops come with a 4-cell battery, which would then obviously greatly reduce the battery life.

[Icewalker]

Yeah, varies by either efficiency or battery size. My new netbook has a quite large battery, and is very small, so it has something like 9 hours of battery life, which is perfect for a netbook. I think that's at all the lowest settings and minimum brightness and such, which is where I keep it.

[Erloas]

Battery life is very simply a cross between how big the battery is and how much power the system uses.

Battery size is fairly standardized with a couple different sizes. Components can vary across the board. A larger LCD, especially one with a bright screen will use more power, LED backlight screens use less power. Solid state drives might use less power and they might not, a lot of reviews have shown that some can use slightly to significantly more then the low power standard hard drives, especially depending on use patterns of the system, a 5400 RPM drive will also use less power then a 7200 RPM drive. The motherboard and processor have probably the biggest single effect on power usage... unless you have a dedicated video card. Dedicated video cards will use more power in idle and a lot more power when being pushed compared to integrated, but of course integrated cards are limited a lot more in what they can do.

Usage patterns also have a big difference on run time. You can run 1-2 browser windows for a long time, if you run any games your battery won't last long at all. Multitasking a lot also uses more power, especially if you are doing something like streaming content which never lets the drives spin down or anything go into standby. As well as running a lot of peripherals on USB ports and such.

The OS also has an impact. I've seen some benchmarks showing some versions of Linux use less power and some use more then various versions of Windows. Win7 I've heard uses less then XP in a lot of cases, but not all. In some cases one OS will use less power on one laptop and more on another. Some OSs will be better for things like encoding while others will be better for browsing.


Of course some changes are big (battery size) and some are small and most come down to how you want to use the system and most are well outside your control anyway, since your options for purchasing a laptop are in the control of the company making them and not you.

[valadil]

Most laptop CPUs will also scale depending on how heavily you're using them. Mine goes back to 0.3ghz when idle. If I use more than ~75% of that, it ups to .8 ghz.

I've also found that certain activities drain the battery faster. Games are obvious. Wireless card, not so much, but it burns battery twice as fast as not using it. That hardly matters though because my laptop is 7 years old and the battery is lucky to last 12 minutes.

[KuReshtin]

Most laptop CPUs will also scale depending on how heavily you're using them. Mine goes back to 0.3ghz when idle. If I use more than ~75% of that, it ups to .8 ghz.

In addition to this, there are now a lot of laptops that come with Switchable Graphics, which helps even more. Basically, the laptop has two different graphics cards. One is a low-powered shared memory Intel Graphics card that doesn't drain the power a whole lot, and the second is an ATI och NVidia graphics card that is used when the machine is plugged in to the AC adapter.
If you want to, you can et the machine to only work on one of them, or switch between the two as part of the power save options. Can save quite a bit of battery.



I've also found that certain activities drain the battery faster. Games are obvious. Wireless card, not so much, but it burns battery twice as fast as not using it. That hardly matters though because my laptop is 7 years old and the battery is lucky to last 12 minutes.

Very much this. Wireless cards drain a LOT of battery power. On my laptop, there's usually a difference of about 15-20 minutes of battery life when having the WiFi card active copmared to when it's shut down. Might not sound too bad, but my battery only lasts about 45-50 minutes as it is, so its quite a significant difference.

[Flickerdart]

You can also find many laptops with ULV (Ultra Low Voltage) processors. Those tend to be slower than their regular counterparts, but use considerably less energy as well. Despite the tiny 4-cell battery, this laptop (Thinkpad X200t) gets 3 hours of battery with wireless on because with only, say, typing up a post on a forum, consumes about 8 watts, and doing more is usually about 11. You'll definitely want something with a 6-cell battery, though, or 9-cell if you don't mind it jutting out of the assembly. On laptops with optical media drives, you can usually remove them and add a modular battery, further extending the capacity.

[Keld Denar]

I'm surprised no one has mentioned this, but LCD size is a pretty huge factor. I have a ~1 year old high performance 17" because it stays stationary a lot when I'm away from home. If I do flip it on in the airport, the battery lasts almost exactly 2 hours with the wireless card on, and ~2 hours 45 minutes with it off. I'm guessing if I had a more traditional 15.6", the battery would last significantly longer.