Battery charging question

[thinkpac]

I have a 9-cell battery in my T60, which I always leave plugged in. I have read the posts from people who suggest that to maximize battery life, you should configure your Power Manager to stop charging at 80%, and then do not start charging until it drops to 20%. So I configured my Power Manager that way back in February. So now, 5 months later, my battery had slowly discharged down to 67%. At that rate, it might be one year before it dropped down to 20%. That's pretty good, I guess, since I won't be subjecting my battery to a lot of charging cycles.

But then we had a power outage last week, and when I booted up the T60, Power Manager reported the battery was at 100%. The T60 had been shut off when the power outage occurred. Any idea why the battery would recharge fully after the power restored?

[crashnburn]

I have a 9-cell battery in my T60, which I always leave plugged in. I have read the posts from people who suggest that to maximize battery life, you should configure your Power Manager to stop charging at 80%, and then do not start charging until it drops to 20%. So I configured my Power Manager that way back in February. So now, 5 months later, my battery had slowly discharged down to 67%. At that rate, it might be one year before it dropped down to 20%. That's pretty good, I guess, since I won't be subjecting my battery to a lot of charging cycles.

But then we had a power outage last week, and when I booted up the T60, Power Manager reported the battery was at 100%. The T60 had been shut off when the power outage occurred. Any idea why the battery would recharge fully after the power restored?

I have the same 9 Cell battery on my T61 and I think they have some Design Fault. My T43 battery is still alive and my T61 battery went towards errors.

[dr_st]

But then we had a power outage last week, and when I booted up the T60, Power Manager reported the battery was at 100%. The T60 had been shut off when the power outage occurred. Any idea why the battery would recharge fully after the power restored?

My experience with the charging thresholds in the Power Manager is that they are not 100% reliable. Sometimes the laptop ignores them for some reason. I haven't figured out the pattern, though.

[TTY]

But then we had a power outage last week, and when I booted up the T60, Power Manager reported the battery was at 100%. The T60 had been shut off when the power outage occurred. Any idea why the battery would recharge fully after the power restored?

If the battery acts up strange, i believe it's a good idea to recalibrate it.

If you set your own charge level thresholds, Lenovo says you should charge the battery to 100% once a quarter.

If you disconnect the AC adapter and remove the battery, the notebook forgets the charge level thresholds. To prevent the notebook from charging the battery after it has forgotten its charge level thresholds, don't connect it to AC power, but start it up on battery. As soon as it has fully booted, it will remember the charge level thresholds. Then shut it down and connect it to AC power.

[dr_st]

Ah, at last somebody shedding some light on it!

So if I understand correctly - the power manager remembers charge levels for each battery, but the embedded controller can only remember one at a time.

So once the power manager identified the battery, it will update the embedded controller, which will retain the information even if the PC is powered off, until the next time you disconnect the battery.

But if you start charging before the power manager had a chance to update the controller information, it will just default to full charge.

It does make sense.

[Norway Pad]

Yes, thank you for confirming this. I have set the thresholds 60%-80% on all my Thinkpads, as I stongly believe this will keep my batteries better. How ever, I wasn't aware of the recomended 100% charge once a quarter. Good to know.

I have also noticed that the laptop sometimes charges the battery to 100% when it is turned off, despite my thresholds. I imagined it had something to do with batteries being taken out and put back, but I wasn't sure. Now I am sure.

[BeeJayEmm]

On all three of our ThinkPads, I have noticed that, although the thresholds are not set to do so, the battery will be recharged to full if the computer is off or in hibernation and the power is interrupted. In my case, the batteries were not removed. I use this "feature" to override the charging thresholds when I need to take the ThinkPad out of the house, as discussed in this thread.