Code/tp-bat-balance - Revision history

ThinkGNU: Put script in

 block, so it can be copy-pasted. Finally a good license.

2025-04-11T07:26:38Z

Put script in <pre> block, so it can be copy-pasted. Finally a good license.

Thinker: Code comments

2009-09-11T18:27:21Z

Code comments

Ttsec: Added case where program started without battery in slot or bay would break program.

2009-09-07T22:36:04Z

Added case where program started without battery in slot or bay would break program.

Thinker: Battery balancing script

2009-08-15T03:48:23Z

Battery balancing script

New page

#!/usr/bin/perl
# Keep two ThinkPad batteries (system battery and UltraBay) at similar charge levels
# during discharge by switching back and forth. This reduces wear on the UltraBay
# battery, compared to the hardware's default strategy of fully draining the UltraBay
# battery before switching to the system battery.
# WARNING: This script is experimental and uses undocumented hardware features.
# WARNING: If this script crashes, your battery may be forced to keep draining until empty.
# Distributed under the terms of the GNU General Public License v2 or later.

use strict;
use warnings;
use File::Slurp;

my $thresh = 3; # difference between battery charge levels that justifies switching (hysteresis)

my $default_discharge = 0; # the battery that's discharged as first priority by the BIOS
my $smapi_dir = '/sys/devices/platform/smapi';

my $ac_connected;
my @bat_installed;
my @bat_remaining;
my @bat_state;
my @bat_power_avg;
my @bat_force_discharge;

$SIG{'INT'} = $SIG{'QUIT'} = $SIG{'TERM'} = sub { die("# Killed by SIG$_[0]\n"); };

sub read_chomp_file {
my ($filename) = @_;
my ($x) = read_file($filename) or die "Cannot read $filename\n";
chomp($x);
return $x;
}

sub read_status {
$ac_connected = read_chomp_file("$smapi_dir/ac_connected");
for my $b (0..1) {
$bat_installed[$b] = read_chomp_file("$smapi_dir/BAT$b/installed");
$bat_force_discharge[$b] = read_chomp_file("$smapi_dir/BAT$b/force_discharge");
if ($bat_installed[$b]) {
$bat_remaining[$b] = read_chomp_file("$smapi_dir/BAT$b/remaining_percent");
$bat_state[$b] = read_chomp_file("$smapi_dir/BAT$b/state");
$bat_power_avg[$b] = read_chomp_file("$smapi_dir/BAT$b/power_avg") / 1000.0;
}
}
}

sub print_status {
print " ";
sub print_bat {
my ($b) = @_;
my ($ll,$lr,$rl,$rr) = $b ? ('-','>','<','-') : ('<','-','-','>');
my $icon = sprintf("[%3s]", $bat_installed[$b] ? $bat_remaining[$b]."%" : "");
my $arrow;
my $state = $bat_state[$b];
if ($state eq 'charging') {
$arrow = sprintf("$ll--%4.1f--$lr", $bat_power_avg[$b]);
} elsif ($state eq 'discharging') {
$arrow = sprintf("$rl--%4.1f--$rr", -$bat_power_avg[$b]);
} elsif ($state eq 'idle') {
$arrow = " ";
} else {
die "Unknown state $state for battery $b";
}
print($b ? "$arrow$icon" : "$icon$arrow");
}
print_bat(0);
print($ac_connected ? ' {AC} ' : ' { } ');
print_bat(1);
print("\n");
}

sub choose_discharge {
# Choose which battery to discharge

sub set_force_discharge {
my ($b,$on) = @_;
return if $b!=$default_discharge; # the non-default battery will be discharged only when necessary anyway
return if $bat_force_discharge[$b]==$on;
write_file("$smapi_dir/BAT$b/force_discharge", ($on?'1':'0')) or die ("Cannot write to $smapi_dir/BAT$b/force_discharge: $!\n");
print("# setting force_discharge on battery $b to $on\n");
$bat_force_discharge[$b] = $on;
}

if ($ac_connected || !$bat_installed[0] || !$bat_installed[1]) {
for $b (0..1) {
set_force_discharge($b,0);
}
} else {
if ($bat_remaining[0] > $bat_remaining[1] + $thresh) {
set_force_discharge(0,1);
set_force_discharge(1,0);
} elsif ($bat_remaining[1] > $bat_remaining[0] + $thresh) {
set_force_discharge(0,0);
set_force_discharge(1,1);
}
}
}

while (1) {
read_status;
print_status;
choose_discharge;
sleep(5);
}

END {
print("# Cleanup\n");
write_file("$smapi_dir/BAT0/force_discharge", ('0'));
write_file("$smapi_dir/BAT1/force_discharge", ('0'));
}

@@ Line 1: / Line 1: @@
 #!/usr/bin/perl
 # Keep two ThinkPad batteries (system battery and UltraBay) at similar charge levels
@@ Line 112: / Line 113: @@
    write_file("$smapi_dir/BAT1/force_discharge", ('0'));
+}

@@ Line 33: / Line 33: @@
+}
 sub read_status {
    $ac_connected = read_chomp_file("$smapi_dir/ac_connected");
@@ Line 47: / Line 48: @@
+}
 sub print_status {
    print "   ";
@@ Line 72: / Line 74: @@
+}
 sub choose_discharge {
    sub set_force_discharge {
      my ($b,$on) = @_;

@@ Line 43: / Line 43: @@
        $bat_power_avg[$b] = read_chomp_file("$smapi_dir/BAT$b/power_avg") / 1000.0;
+     }
+   }
+}
@@ Line 58: / Line 59: @@
      } elsif ($state eq 'discharging') {
        $arrow = sprintf("$rl--%4.1f--$rr", -$bat_power_avg[$b]);
-     } elsif ($state eq 'idle') {
+     } elsif ($state eq 'idle' || $state eq 'none') {  #Added none to cover case with no battery in slot when program was started.
        $arrow = "          ";
      } else {