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View Full Version : powerbook battery issues :\



mechcon
20th November 2006, 01:41 PM
Interesting issue, I did a full battery recharge after draining it out completely (to the extend it went to sleep) now that it got to 100%, I thought okay,I'll unplug it, it eventually got to 98%, so then I plug it back into the ac, and the status is on "Charged".

So I unplug it again, I wait till it gets to 97%, plug it back in, Charged, so I unplug it, and so forth, till I got to 94% and it stated "Calculating"

Is my battery on it's way out? or is it just part of it is draining permanently?

forgie
20th November 2006, 02:20 PM
The last part of the charge cycle is the part where the batteries get damaged (this is true of NiMH, and I think it's true for Li-Ion too). The charge controller in your PB will not want to damage the battery, and it's very hard to know when to stop charging if it's already over 90%. If you discharge it down to say 60% then charge it up again you should get 100%.

mechcon
20th November 2006, 03:57 PM
yeah it seems to be fine now! so the last part of the charge cycle bit.. is that what i've got?

forgie
20th November 2006, 04:03 PM
It's not a problem, it's just a limitation of the battery technology. The battery controller can only make an estimate of when to stop charging, and the longer the charging time, the more accurate it will be. If the charge controller starts charging at 90%, it will have a much higher error rate in terms of predicting when to stop charging, which means that the chances of overcharging (which leads to shorter battery life) are increased. To combat this, it would appear as though the charge controllers "play it safe" and will refuse to charge that last little bit of the battery if it's not sure that it won't be damaging it.

This is the best way to do it with the current state of battery technology. Your PB is basically saying "I don't know whether I am going to damage the battery, so I won't charge the last little bit". There's nothing wrong with your battery, or the charging system. It's just that there are uncertainties involved, and (thankfully) the current battery charger systems seem to play it safe rather then charging that last little bit when it might not be safe to do so.

Older laptops may well have kept on charging, which would lead to overcharging and long-term damage of the battery itself. The reason this whole thing is an issue is that there is no perfect way to tell when a battery cell is 100% charged - there are indicators (voltage and temperature) but they are not 100% perfect.