This is sample output - yours may be different.
# contents of battery.txt . I removed the AC plug and started the script
start
Seg Out 19 00:00:22 BRST 2009
Battery 1: charged, 100%
Seg Out 19 00:01:22 BRST 2009
Battery 1: discharging, 98%, 01:58:22 remaining
Seg Out 19 00:02:22 BRST 2009
Battery 1: discharging, 97%, 01:34:33 remaining
Seg Out 19 00:03:22 BRST 2009
Battery 1: discharging, 96%, 01:56:23 remaining
Seg Out 19 00:04:22 BRST 2009
Battery 1: discharging, 95%, 01:51:19 remaining
Seg Out 19 00:05:22 BRST 2009
Battery 1: discharging, 94%, 01:48:14 remaining
Seg Out 19 00:06:22 BRST 2009
Battery 1: discharging, 93%, 01:51:50 remaining
Seg Out 19 00:07:22 BRST 2009
Battery 1: discharging, 92%, 01:41:49 remaining
Seg Out 19 00:08:22 BRST 2009
Battery 1: discharging, 91%, 01:43:47 remaining
Seg Out 19 00:09:22 BRST 2009
Battery 1: discharging, 90%, 01:37:15 remaining
Seg Out 19 00:10:22 BRST 2009
Battery 1: discharging, 89%, 01:34:37 remaining
Seg Out 19 00:11:22 BRST 2009
Battery 1: discharging, 88%, 01:39:25 remaining
Seg Out 19 00:12:22 BRST 2009
Battery 1: discharging, 87%, 01:39:24 remaining
Seg Out 19 00:13:22 BRST 2009
Battery 1: discharging, 86%, 01:41:27 remaining
Seg Out 19 00:14:22 BRST 2009
Battery 1: discharging, 86%, 01:38:22 remaining
Seg Out 19 00:15:22 BRST 2009
Battery 1: discharging, 85%, 01:36:41 remaining
Seg Out 19 00:16:22 BRST 2009
Battery 1: discharging, 84%, 01:28:19 remaining
Seg Out 19 00:17:22 BRST 2009
Battery 1: discharging, 83%, 01:34:30 remaining
Seg Out 19 00:18:22 BRST 2009
Battery 1: discharging, 82%, 01:34:14 remaining
Seg Out 19 00:19:22 BRST 2009
Battery 1: discharging, 81%, 01:32:49 remaining
Seg Out 19 00:20:22 BRST 2009
Battery 1: discharging, 80%, 01:32:51 remaining
Seg Out 19 00:21:22 BRST 2009
Battery 1: discharging, 79%, 01:28:38 remaining
Seg Out 19 00:22:22 BRST 2009
Battery 1: discharging, 78%, 01:30:43 remaining
Seg Out 19 00:23:22 BRST 2009
Battery 1: discharging, 77%, 01:29:01 remaining
Seg Out 19 00:24:22 BRST 2009
Battery 1: discharging, 76%, 01:28:07 remaining
Seg Out 19 00:25:23 BRST 2009
Battery 1: discharging, 75%, 01:26:47 remaining
Seg Out 19 00:26:23 BRST 2009
Battery 1: discharging, 74%, 01:21:07 remaining
Seg Out 19 00:27:23 BRST 2009
Battery 1: discharging, 74%, 01:20:57 remaining
Seg Out 19 00:28:23 BRST 2009
Battery 1: discharging, 73%, 01:24:13 remaining
Seg Out 19 00:29:23 BRST 2009
Battery 1: discharging, 72%, 01:22:05 remaining
Seg Out 19 00:30:23 BRST 2009
Battery 1: discharging, 71%, 01:18:35 remaining
Seg Out 19 00:31:23 BRST 2009
Battery 1: discharging, 70%, 01:18:10 remaining
Seg Out 19 00:32:23 BRST 2009
Battery 1: discharging, 69%, 01:20:03 remaining
Seg Out 19 00:33:23 BRST 2009
Battery 1: discharging, 68%, 01:02:24 remaining
Seg Out 19 00:34:23 BRST 2009
Battery 1: discharging, 67%, 01:16:06 remaining
Seg Out 19 00:35:23 BRST 2009
Battery 1: discharging, 66%, 01:15:25 remaining
Seg Out 19 00:36:23 BRST 2009
Battery 1: discharging, 65%, 01:11:21 remaining
Seg Out 19 00:37:23 BRST 2009
Battery 1: discharging, 65%, 01:52:59 remaining
Seg Out 19 00:38:23 BRST 2009
Battery 1: discharging, 64%, 01:51:40 remaining
Seg Out 19 00:39:23 BRST 2009
Battery 1: discharging, 63%, 01:47:24 remaining
Seg Out 19 00:40:23 BRST 2009
Battery 1: discharging, 63%, 01:45:28 remaining
Seg Out 19 00:41:23 BRST 2009
Battery 1: discharging, 62%, 01:49:21 remaining
Seg Out 19 00:42:23 BRST 2009
Battery 1: discharging, 62%, 01:48:55 remaining
Seg Out 19 00:43:23 BRST 2009
Battery 1: discharging, 61%, 01:46:37 remaining
Seg Out 19 00:44:23 BRST 2009
Battery 1: discharging, 60%, 01:43:37 remaining
Seg Out 19 00:45:23 BRST 2009
Battery 1: discharging, 60%, 01:34:41 remaining
Seg Out 19 00:46:23 BRST 2009
Battery 1: discharging, 59%, 01:42:59 remaining
Seg Out 19 00:47:23 BRST 2009
Battery 1: discharging, 59%, 01:34:59 remaining
Seg Out 19 00:48:23 BRST 2009
Battery 1: discharging, 58%, 01:34:05 remaining
Seg Out 19 00:49:23 BRST 2009
Battery 1: discharging, 57%, 01:35:02 remaining
Seg Out 19 00:50:23 BRST 2009
Battery 1: discharging, 57%, 01:38:28 remaining
Seg Out 19 00:51:23 BRST 2009
Battery 1: discharging, 56%, 01:32:56 remaining
Seg Out 19 00:52:23 BRST 2009
Battery 1: discharging, 55%, 01:38:18 remaining
Seg Out 19 00:53:23 BRST 2009
Battery 1: discharging, 55%, 01:35:09 remaining
Seg Out 19 00:54:23 BRST 2009
Battery 1: discharging, 54%, 01:29:34 remaining
Seg Out 19 00:55:23 BRST 2009
Battery 1: discharging, 54%, 01:28:44 remaining
Seg Out 19 00:56:23 BRST 2009
Battery 1: discharging, 53%, 01:25:33 remaining
Seg Out 19 00:57:23 BRST 2009
Battery 1: discharging, 52%, 01:28:49 remaining
Seg Out 19 00:58:23 BRST 2009
Battery 1: discharging, 52%, 01:28:03 remaining
Seg Out 19 00:59:23 BRST 2009
Battery 1: discharging, 51%, 01:26:41 remaining
Seg Out 19 01:00:23 BRST 2009
Battery 1: discharging, 50%, 01:27:20 remaining
Seg Out 19 01:01:23 BRST 2009
Battery 1: discharging, 50%, 01:26:16 remaining
Seg Out 19 01:02:23 BRST 2009
Battery 1: discharging, 49%, 01:25:15 remaining
Seg Out 19 01:03:24 BRST 2009
Battery 1: discharging, 49%, 01:03:48 remaining
Seg Out 19 01:04:24 BRST 2009
Battery 1: discharging, 48%, 01:22:12 remaining
Seg Out 19 01:05:24 BRST 2009
Battery 1: discharging, 47%, 01:21:18 remaining
Seg Out 19 01:06:24 BRST 2009
Battery 1: discharging, 47%, 01:17:24 remaining
Seg Out 19 01:07:24 BRST 2009
Battery 1: discharging, 46%, 01:21:53 remaining
Seg Out 19 01:08:24 BRST 2009
Battery 1: discharging, 45%, 01:18:38 remaining
Seg Out 19 01:09:24 BRST 2009
Battery 1: discharging, 45%, 01:17:38 remaining
Seg Out 19 01:10:24 BRST 2009
Battery 1: discharging, 44%, 01:17:43 remaining
Seg Out 19 01:11:24 BRST 2009
Battery 1: discharging, 44%, 01:16:04 remaining
Seg Out 19 01:12:24 BRST 2009
Battery 1: discharging, 43%, 01:16:23 remaining
Seg Out 19 01:13:24 BRST 2009
Battery 1: discharging, 42%, 01:03:56 remaining
Seg Out 19 01:14:24 BRST 2009
Battery 1: discharging, 42%, 01:03:20 remaining
Seg Out 19 01:15:24 BRST 2009
Battery 1: discharging, 41%, 01:03:10 remaining
Seg Out 19 01:16:24 BRST 2009
Battery 1: discharging, 41%, 01:09:42 remaining
Seg Out 19 01:17:24 BRST 2009
Battery 1: discharging, 40%, 01:05:06 remaining
Seg Out 19 01:18:24 BRST 2009
Battery 1: discharging, 39%, 01:05:20 remaining
Seg Out 19 01:19:24 BRST 2009
Battery 1: discharging, 38%, 01:05:57 remaining
Seg Out 19 01:20:24 BRST 2009
Battery 1: discharging, 38%, 01:03:46 remaining
Seg Out 19 01:21:24 BRST 2009
Battery 1: discharging, 37%, 01:00:13 remaining
Seg Out 19 01:22:24 BRST 2009
Battery 1: discharging, 37%, 01:01:40 remaining
Seg Out 19 01:23:24 BRST 2009
Battery 1: discharging, 36%, 00:59:12 remaining
Seg Out 19 01:24:24 BRST 2009
Battery 1: discharging, 35%, 01:00:31 remaining
Seg Out 19 01:25:24 BRST 2009
Battery 1: discharging, 35%, 00:58:29 remaining
Seg Out 19 01:26:24 BRST 2009
Battery 1: discharging, 34%, 00:57:23 remaining
Seg Out 19 01:27:24 BRST 2009
Battery 1: discharging, 33%, 00:57:10 remaining
Seg Out 19 01:28:24 BRST 2009
Battery 1: discharging, 33%, 00:55:25 remaining
Seg Out 19 01:29:24 BRST 2009
Battery 1: discharging, 32%, 00:55:52 remaining
Seg Out 19 01:30:24 BRST 2009
Battery 1: discharging, 32%, 00:54:45 remaining
Seg Out 19 01:31:24 BRST 2009
Battery 1: discharging, 31%, 00:53:34 remaining
Seg Out 19 01:32:24 BRST 2009
Battery 1: discharging, 30%, 00:53:14 remaining
Seg Out 19 01:33:24 BRST 2009
Battery 1: discharging, 30%, 00:48:24 remaining
Seg Out 19 01:34:24 BRST 2009
Battery 1: discharging, 29%, 00:47:46 remaining
Seg Out 19 01:35:24 BRST 2009
Battery 1: discharging, 28%, 00:49:57 remaining
Seg Out 19 01:36:24 BRST 2009
Battery 1: discharging, 28%, 00:47:10 remaining
Seg Out 19 01:37:24 BRST 2009
Battery 1: discharging, 27%, 00:47:04 remaining
Seg Out 19 01:38:24 BRST 2009
Battery 1: discharging, 26%, 00:44:00 remaining
Seg Out 19 01:39:24 BRST 2009
Battery 1: discharging, 26%, 00:40:29 remaining
Seg Out 19 01:40:25 BRST 2009
Battery 1: discharging, 25%, 00:39:58 remaining
Seg Out 19 01:41:25 BRST 2009
Battery 1: discharging, 24%, 00:38:41 remaining
Seg Out 19 01:42:25 BRST 2009
Battery 1: discharging, 24%, 00:40:41 remaining
Seg Out 19 01:43:25 BRST 2009
Battery 1: discharging, 23%, 00:36:22 remaining
Seg Out 19 01:44:25 BRST 2009
Battery 1: discharging, 22%, 00:38:15 remaining
Seg Out 19 01:45:25 BRST 2009
Battery 1: discharging, 22%, 00:36:59 remaining
Seg Out 19 01:46:25 BRST 2009
Battery 1: discharging, 21%, 00:34:42 remaining
Seg Out 19 01:47:25 BRST 2009
Battery 1: discharging, 20%, 00:38:37 remaining
Seg Out 19 01:48:25 BRST 2009
Battery 1: discharging, 20%, 00:36:23 remaining
Seg Out 19 01:49:25 BRST 2009
Battery 1: discharging, 19%, 00:32:27 remaining
Seg Out 19 01:50:25 BRST 2009
Battery 1: discharging, 19%, 00:33:38 remaining
Seg Out 19 01:51:25 BRST 2009
Battery 1: discharging, 18%, 00:33:25 remaining
Seg Out 19 01:52:25 BRST 2009
Battery 1: discharging, 17%, 00:32:01 remaining
Seg Out 19 01:53:25 BRST 2009
Battery 1: discharging, 17%, 00:22:47 remaining
Seg Out 19 01:54:25 BRST 2009
Battery 1: discharging, 16%, 00:29:30 remaining
Seg Out 19 01:55:25 BRST 2009
Battery 1: discharging, 16%, 00:26:29 remaining
Seg Out 19 01:56:25 BRST 2009
Battery 1: discharging, 15%, 00:28:22 remaining
Seg Out 19 01:57:25 BRST 2009
Battery 1: discharging, 14%, 00:27:20 remaining
Seg Out 19 01:58:25 BRST 2009
Battery 1: discharging, 14%, 00:25:20 remaining
Seg Out 19 01:59:25 BRST 2009
Battery 1: discharging, 13%, 00:23:34 remaining
Seg Out 19 02:00:25 BRST 2009
Battery 1: discharging, 13%, 00:23:26 remaining
Seg Out 19 02:01:25 BRST 2009
Battery 1: discharging, 12%, 00:22:14 remaining
Seg Out 19 02:02:25 BRST 2009
Battery 1: discharging, 11%, 00:19:04 remaining
Seg Out 19 02:03:25 BRST 2009
Battery 1: discharging, 11%, 00:18:54 remaining
Seg Out 19 02:04:25 BRST 2009
Battery 1: discharging, 10%, 00:18:21 remaining
Seg Out 19 02:05:25 BRST 2009
Battery 1: discharging, 9%, 00:17:33 remaining
Seg Out 19 02:06:25 BRST 2009
Battery 1: discharging, 9%, 00:16:34 remaining
Seg Out 19 02:07:25 BRST 2009
Battery 1: discharging, 8%, 00:14:15 remaining
Seg Out 19 02:08:25 BRST 2009
Battery 1: discharging, 8%, 00:14:06 remaining
Seg Out 19 02:09:25 BRST 2009
Battery 1: discharging, 7%, 00:13:08 remaining
Seg Out 19 02:10:25 BRST 2009
Battery 1: discharging, 7%, 00:11:48 remaining
Seg Out 19 02:11:25 BRST 2009
Battery 1: discharging, 7%, 00:11:57 remaining
Seg Out 19 02:12:25 BRST 2009
Battery 1: discharging, 6%, 00:11:07 remaining
Seg Out 19 02:13:25 BRST 2009
Battery 1: discharging, 6%, 00:08:01 remaining
Seg Out 19 02:14:25 BRST 2009
Battery 1: discharging, 5%, 00:09:45 remaining
Seg Out 19 02:15:25 BRST 2009
Battery 1: discharging, 4%, 00:08:12 remaining
Seg Out 19 02:16:25 BRST 2009
Battery 1: discharging, 4%, 00:06:40 remaining
Seg Out 19 02:17:25 BRST 2009
Battery 1: discharging, 3%, 00:06:09 remaining
Seg Out 19 02:18:26 BRST 2009
Battery 1: discharging, 3%, 00:04:58 remaining
Seg Out 19 02:19:26 BRST 2009
Battery 1: discharging, 3%, 00:04:58 remaining
Seg Out 19 02:20:26 BRST 2009
Battery 1: discharging, 3%, 00:04:57 remaining
Seg Out 19 02:21:26 BRST 2009
Battery 1: discharging, 3%, 00:03:27 remaining
Seg Out 19 02:22:26 BRST 2009
Battery 1: discharging, 3%, 00:03:36 remaining
Seg Out 19 02:23:26 BRST 2009
Battery 1: discharging, 2%, 00:03:22 remaining
Seg Out 19 02:24:26 BRST 2009
Battery 1: discharging, 2%, 00:02:21 remaining
Seg Out 19 02:25:26 BRST 2009
Battery 1: discharging, 1%, 00:01:24 remaining
# time of death shows 02:25, wich means 26 min more than initially predicted... Now I know my battery lasts 2 hours and 25 minutes...