07-15-2010 04:40 AM
For proper management of "SMART" Li Ion laptop batteries, one must regularly recalibrate the battery. I've had a very hard time getting recalibration to work on my Toshiba M400 laptops.
Has anyone found a reliable way to get recalibration to work properly?
The key missing element: enabling the laptop to stay powered on long enough so the battery recognizes it has hit the low-voltage "recalibration" point. Unless it does this, it will never properly recalibrate.
For those who don't know, here is a brief intro to proper recalibration (for ANY laptop):
1) The goal: help the battery identify how much power is available for use, and how the voltage varies over the drain cycle.
2) The overall picture: total power used from very-full charge to very-empty drain is measured.
3) Typical problems: draining from not-so-full charge "cheats" you of useful life. Never draining all the way means never recalibrating.
4) Helpful tool: Passmark BatteryMon (even the 30 day free trial version) helps see what is happening.
5) How to do it:
a) Charge the battery. All the way. Unplug and replug it and wait again, just to be sure
b) Unplug. DO NOT plug in again until step (c) is complete. Even a brief jolt of charging will cancel the recalibration.
c) Discharge, gently, ALL the way. Don't try to drain too quickly; just have the settings at a normal level. BUT you must be sure all "power down if battery low" settings are disabled. You want the laptop to be FULLY drained. In fact, once it shuts down, I pull the battery, plug it back in, and power on again, at least to the BIOS.
d) Now you can charge again and use as normal.
Step (a) triggers the "could be a valid recalibration" flag. Step (c) triggers "this was a recalibration" flag.
If you've successfully recalibrated, the total available charge value should change. Different batteries follow various rules on this: some only change the total available charge by a certain maximum amount (eg 512 mwH) with each recalibration, so if your battery is wayyy off, you may have to recalibrate several times.
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