Linked by Thom Holwerda on Mon 8th Feb 2010 23:55 UTC
Windows The past few weeks or so, there's been a lot of interest in a supposed battery status report bug in Windows 7. After installing Windows 7, some users reported seeing "consider replacing your battery"-warnings in systems that appeared to be operating just fine on Windows XP or Vista. After extensive research, Steven Sinofsky has now explained on the Engineering 7 blog that the fault is not with Windows 7 - it really, really is your battery.
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Two issues
by Delgarde on Tue 9th Feb 2010 01:25 UTC
Delgarde
Member since:
2008-08-19

Reading the post, and it's comments, there seem to be two quite separate issues people are complaining about. One is that W7 reports their battery as failing - well, that seems correct behavour, if this article is to be believed.

The other, though, is people reporting greatly reduced battery life after installing W7 - a fully-charged laptop might run for a couple of hours under XP, but less than half that under W7. That seems a bit more concerning...

Reply Score: 3

RE: Two issues
by Al2001 on Tue 9th Feb 2010 01:34 in reply to "Two issues"
Al2001 Member since:
2005-07-06

Where is your citation?

After browsing multiple web sites the worst case I could find was around 20% less battery time under Win7, most showed neglible difference and one even found an increase.

Reply Parent Score: 1

RE: Two issues
by umccullough on Tue 9th Feb 2010 01:35 in reply to "Two issues"
umccullough Member since:
2006-01-26

The other, though, is people reporting greatly reduced battery life after installing W7 - a fully-charged laptop might run for a couple of hours under XP, but less than half that under W7. That seems a bit more concerning...


Or it just means that according to the battery's health reported back to the OS, it is "dead", but Windows XP just ignored it while Windows 7 actually "listens" and shuts down properly.

Warning: rambling about batteries about to occur:

Battery health monitoring sensors can be pretty crappy sometimes - I've experienced a lot of inconsistent battery life meters - sometimes being able to disable an OS's built-in auto-shutdown feature and gain a lot of extra time with the battery.

Careful playing this game though, as this can actually cause premature failure of individual cells in the battery. When one cell in a mult-cell battery pack is completely discharged, you can often continue using the pack as it's still producing enough voltage to power your device. However, once a cell has discharged completely, continuing to run it in series with other cells will reverse-charge the cell which will eventually irreparably ruin it, making it a permanently-dead cell.

Proper battery health monitoring measures voltage levels and drop-rate along with temperature of the entire pack to detect irregularities and shut down the discharge or charge cycle completely.

Common premature failures of battery packs are caused by mismatched cells - cells that have different peak charge capacities. This causes a pack to only charge partially when one or more of the cells "peak", leaving the remaining cells partially filled. Likewise, the cells with the least capacity will discharge first, and will start to reverse-charge causing more damage to them. Eventually, you end up with a 6-cell pack that only has 5 working cells... it will fail health monitoring tests.

There, sorry... just a long diatribe from someone who spent a lot of time learning about rechargeable batteries while messing with R/C cars ;)

Reply Parent Score: 5

RE[2]: Two issues
by akro on Tue 9th Feb 2010 02:29 in reply to "RE: Two issues"
akro Member since:
2005-07-06

Ah the A-main battery dump with 10 seconds left....


TURN MARSHALL!!!!!!!

Reply Parent Score: 1

RE[2]: Two issues
by smashIt on Tue 9th Feb 2010 17:21 in reply to "RE: Two issues"
smashIt Member since:
2005-07-06

When one cell in a mult-cell battery pack is completely discharged, you can often continue using the pack as it's still producing enough voltage to power your device. However, once a cell has discharged completely, continuing to run it in series with other cells will reverse-charge the cell which will eventually irreparably ruin it, making it a permanently-dead cell.


that was true for nicd and pb cells
modern lithium cells already die when deep-discharged (less than ~3v)
as great as their capacity is, as sensible they are...

Reply Parent Score: 2

RE: Two issues
by darknexus on Tue 9th Feb 2010 03:09 in reply to "Two issues"
darknexus Member since:
2008-07-15

I can't say I've seen a 50% decrease, but I've seen some issues where by Windows 7 will not get as much life out of a battery as XP or Linux. I've seen about a 15% reduction on some machines, and I'm 99.99% sure that it wasn't due to an unhealthy battery. I suspect, personally, it was the result of badly-behaved acpi bios coupled with no acpi drivers for win 7 on those machines, while XP and Linux both had support for all the ACPI features once configured. As is typical with Windows, the majority of problems aren't caused by Windows itself but by incompatible and/or poorly-written drivers. Other than Malware, drivers are the number one problem I see when dealing with Windows and I suspect it is mostly that to blame for reduced battery life under 7 on a lot of machines.

Reply Parent Score: 2

RE[2]: Two issues
by umccullough on Tue 9th Feb 2010 03:41 in reply to "RE: Two issues"
umccullough Member since:
2006-01-26

I suspect, personally, it was the result of badly-behaved acpi bios coupled with no acpi drivers for win 7 on those machines, while XP and Linux both had support for all the ACPI features once configured. As is typical with Windows, the majority of problems aren't caused by Windows itself but by incompatible and/or poorly-written drivers.


I'm fairly certain that, unless the manufacturer of your BIOS is an idiot, ACPI-based power management shouldn't really require any special drivers. I mean, that's sort of the whole point of standardizing that isn't it?

I've read that some BIOS will serve up different ACPI tables based on the OS they detect is running. A lot of retarded manufacturers have hardcoded their ACPI tables to spit out something different if they don't detect Windows XP... perhaps that is what you're referring to?

I've rarely installed the crapware "battery/power management" software that comes with a laptop - more often than not it provides little benefit over the stock features, other than providing some fancy UI and some extra software-based "profile" features for those who like to fiddle.

Edit: OK, I suppose some of those crapware programs probably replace the "missing" functionality from Windows XP - but from what I read, Windows 7 supposedly fills that gap again.

Edited 2010-02-09 03:43 UTC

Reply Parent Score: 2

RE[2]: Two issues
by leavengood on Wed 10th Feb 2010 02:35 in reply to "RE: Two issues"
leavengood Member since:
2006-12-13

Other than Malware, drivers are the number one problem I see when dealing with Windows and I suspect it is mostly that to blame for reduced battery life under 7 on a lot of machines.


It is pretty ironic, yet not surprising, that one of the top problems with Windows 7 is lack of drivers, since that is also the top problem in "alternative" OSes. I wonder when these hardware manufacturers are going to get it through their thick skulls that producing hardware and drivers which only works with Windows XP is stupid. They should at least document how there crappy hardware works so other people can write proper drivers.

Reply Parent Score: 1

RE: Two issues
by Cody Evans on Tue 9th Feb 2010 03:41 in reply to "Two issues"
Cody Evans Member since:
2009-08-14

My Acer Aspire 1 D150 gets same battery life in everything. Around 5 hours of battery life in WinXP, WIn7, and Ubuntu Netbook Remix.

Reply Parent Score: 2