[ltp] Battery Cell Replacement

FeRD linux-thinkpad@linux-thinkpad.org
Wed, 15 Mar 2006 15:41:00 -0500

Ron Joffe wrote:
> But looking back, I think I need to understand the battery control circuitry 
> better. Booting into windows, the machine almost immediately tried going into 
> hibernation mode (since it thinks that the battery has a capacity of all of 5 
> minutes). And the battery indicator blinking is quite annoying.
You might be able to convince it that the battery has more capacity than 
it used to by taking an old trick from the NiCd battery days -- run a 
few complete discharge/charge cycles on the machine. Even though battery 
memory isn't a problem anymore with LIon batteries, the control 
circuitry seems to have its own "memory" of the battery's state.

Not long after I first got my used, non-brick T22 battery (to replace 
the lifeless brick it was sold to me with), I accidentally cycled the 
battery a few times. (It was in a room with no power outlet positioned 
nearby the only spot where I could get a wireless signal, and kept 
forgetting to run and plug it in often enough.) I had all 
power-management turned off COMPLETELY in the BIOS and in my Linux configs.

I'd first noticed, while working on the machine, that the new battery 
was keeping the machine running quite a while longer than the 
battery-life-timer reached the "0:00" mark. Then, at the end of the 
night, I discovered that the "Remaining Capacity" indication in 
/proc/acpi/battery/<mumble> at 100% charge had actually RISEN from the 
point it had been at before I accidentally cycled the thing. In my case 
it wasn't much, a few 100 mWh, but the same trick may work for your 
battery. Presumably, the control circuitry noticed that it was hitting 
the 0 mark on its calibrated battery-life scale WAY before it stopped 
spitting out power, and corrected.

My specific 'method' (to madness) was to run the computer with 
power-management disabled systemwide, unplugged, until the machine 
actually lost power and died. (Might be a good idea to keep the 
filesystems relatively quiescent towards the end of the period.) Then, 
I'd take the machine over to its power supply and plug it in to charge,  
still powered off. Lather, rinse, repeat.