2010/11/10 Fatih Tümen <fthtmn+gen...@gmail.com>: > On Tue, Nov 9, 2010 at 23:52, Paul Hartman > <paul.hartman+gen...@gmail.com> wrote: >> Hi, >> >> I have a laptop running Gentoo (with dual-boot to Windows XP). It was >> manufactured in 2004 and battery life have been consistent for all >> those years. However, it sat dormant for almost a year, after which I >> did a few days worth of updating to bring it up to current kernel and >> ~amd64 package levels. There are two issues that have arisen: >> >> 1) The smart battery is not so smart anymore. It only charges about >> halfway, then the charging light turns green and it stops. Effective >> battery capacity is about one-third of what it used to be. From what I >> understand, while Li-ion don't have "memory" like old Ni-Cd batteries, >> the "smart" circuitry cannot account for power drain that happens when >> the battery is not in use. Say the battery lost half of its power >> while it was in storage, so the chip thinks charge is at one level >> when it is really much lower. When recharging, it stops when it is >> "full" even though it's only halfway there. >> >> Has anyone successfully re-calibrated one of these batteries to >> recognize a larger capacity? >> >> My understanding is that, to do this, I should discharge at a constant >> rate until it is empty, then charge to full. Repeat ?? times. I've >> drained the poor little battery after regular usage (not a constant >> rate of discharge) a few times and haven't noticed any change so far. >> So I'm probably doing it wrong (or completely misunderstanding...) >> > > AFAIK, this is the advised way to dis/charge Li-ion batteries to keep > their performance up. But since you left it to sleep for a year, you > probably lost some of the cells to death. You can perhaps try keep > doing that not to loose any more of them.
After consulting my laptop manual, it recommends doing full discharge/charge cycle once a month, to remove battery when operating solely on AC power, and to remove battery when laptop is not in use. I didn't do any of those things. > If youre planning to use this battery, either try other battery > monitors or have a script to calculate above values periodically and > give a warning. Otherwise at some point your system will get as > corrupted as your battery. Good luck. Thanks, it seems my poor batteries may have been killed then. My laptop used to last about 90 minutes in Linux or 2.5 hours in Windows XP, at the beginning of this year. Under extreme load (frequency scaling disabled) it would last about 30 minutes. Last night I took it to full charge, put in memtest86+ boot CD and the system lasted 9 minutes before battery was drained. So that matches the 1/3 batter life I experienced under normal usage, too. I just read somewhere on WWW that sometimes better calibration can be achieved by leaving battery completely drained for some time (more than 5 hours) before plugging the charger back in. So I'll try that as one last desperate hope. If the cells are dead then I can't do any more harm to them so why not try it? :) Now, since this is an old laptop (6 years) I am skeptical about buying a replacement battery that may have been sitting in a stockroom for several years. Local battery store wants more than US$100 for a "name brand" replacement (Rayovac). Online, I can find one for less than half that price, but I am really suspicious about the quality. My past experience of buying generic laptop batteries online has not been good. Don't fit properly, poor lifespan, etc. Of course Acer does not sell the batteries for my laptop anymore, so getting an original battery is not an option. Has anyone tried to replace the cells inside their own battery? I'm reading this site: http://www.electronics-lab.com/articles/Li_Ion_reconstruct/ Seems kind of dangerous... I can't price the cells because I haven't opened my battery pack, so I don't know if it's really any cheaper than buying a new one.
