[ltp] Re: ThinkPad Batteries

[Michael Karcher]

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Am Mittwoch, den 12.11.2008, 22:13 +0000 schrieb Daniel Castro:
> echo 30 > /sys/devices/platform/smapi/BAT0/start_charge_thresh=20
> echo 80 > /sys/devices/platform/smapi/BAT0/stop_charge_thresh=20
> i though that it would charge up to 80% and then run on battery until
> it gets to 30%, then charge again to 80% and so on... isn't that
> what's explected?

These thresholds just inhibit charging: Your laptop decides to start
charging the battery if the charge falls below 30% (by using it on
battery or by self-discharge, the latter needing a very long time), and
keeps charging until 80%. At that point, charging is stopped, but that
does not mean that discharging is startet. The battery is just left
alone. There are ways to force using battery power on AC, see the
documentation, but this is not recommended on normal use.

The sense of the stop_charge_threshold is that charging the last 20% of
the battery is done with high cell voltages (as the cell voltages rises
during charging) and the battery cells are stressed more if the voltage
is higher. The sense of the start_charge_threshold is to keep the
battery at even lower average charge (and voltage) and avoid
charging/discharging cycles.

Regards,
  Michael Karcher

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