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Battery at 95% on T61
Posted: Mon Jul 30, 2007 2:45 pm
by cflutist
Anyone know why my battery is at 95% instead of 100% when the AC adapter is constantly plugged in?
I even powered the T61 off for several hours yesterday thinking that the AC adapter would charge it back to 100%. It did not.
Also, was using my new 90w adapter instead of the 65w adapter if that makes any difference.
Re: Battery at 95% on T61
Posted: Mon Jul 30, 2007 2:50 pm
by NathanA
cflutist wrote:Anyone know why my battery is at 95% instead of 100% when the AC adapter is constantly plugged in?
The batteyr charger has a threshold at which point it will kick in. If the charge level is not below that threshold, the charging circuit will not kick in. This is to prevent uinnecessary wear-and-tear to the battery (Li-Ion batteries are only good for so many charge cycles).
The default threshold level is 96%; however, this is customizable, and it is possible that your settings got changed at some point. You can check to see what your threshold level is set at by going into ThinkVantage Power Manager -> Battery Information tab -> Battery Maintenace, and look at the Charge Thresholds section. There is "Always charge" (the 96% option), a Custom option (specify your own thresholds), and an "Optimize for battery lifespan" which dynamically changes the charging thresholds over time based on some internal algorithm and what it thinks the current health status of your battery is.
If you don't want to change your setting but want to get the battery topped-off nonetheless (perhaps just to check and make sure everything is working properly), then just simply allow your battery to discharge a little more (< 90%) and then plug the power back in; it should go to 100% at that point, I'd think.
-- Nathan
Posted: Mon Jul 30, 2007 3:55 pm
by SHoTTa35
also, just so you know it's not a good idea to have the battery constantly charged at 100%. It will kill the cells faster and you wont have any be able to use it off the battery after a while.
Posted: Mon Jul 30, 2007 4:05 pm
by cflutist
Thanks for your help;
It was set to Always fully charge (start when below 96%, stop at 100%). It does say battery is in good condition.
Posted: Mon Jul 30, 2007 5:49 pm
by bill bolton
SHoTTa35 wrote:also, just so you know it's not a good idea to have the battery constantly charged at 100%. It will kill the cells faster and you wont have any be able to use it off the battery after a while.
The point with the charge thresholds is related to not charging the battery when it really doesn't need it, rather than not having it at 100% charge.
A ThinkPad LiON battery maintained at 100% charge most of the time can last several years before it could be resonably regarded as "killed".
Cheers,
Bill B.