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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RE: Two issues
by umccullough on Tue 9th Feb 2010 01:35 UTC in reply to "Two issues"
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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 ;)

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