How to check if my battery is healthy?

My Lenovo ThinkPad T61 is rather old, and a couple of years ago I had to replace the battery as the old one was dead. Now the replacement battery seems like dying a slow death, but I get conflicting data from xfce4-power-manager. So I'm wondering if there is a way to check whether the battery is healthy. The symptoms are as follows: * The power manager indicates that the battery is fully charged * If I disconnect the AC charger, then the battery status jumps to 47% or similar in less than 5min * And in less than 15min the laptop runs out of juice and shuts down I tried to check upower data: root@malou-laptop:/home/liv# upower --enumerate /org/freedesktop/UPower/devices/line_power_AC /org/freedesktop/UPower/devices/battery_BAT0 root@malou-laptop:/home/liv# upower -i /org/freedesktop/UPower/devices/battery_BAT0 native-path: /sys/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:00/PNP0C09:00/PNP0C0A:00/power_supply/BAT0 vendor: SANYO model: 92P1137 serial: 885 power supply: yes updated: Wed 19 Feb 2014 09:35:37 PM CET (23 seconds ago) has history: yes has statistics: yes battery present: yes rechargeable: yes state: fully-charged energy: 70.38 Wh energy-empty: 0 Wh energy-full: 72.42 Wh energy-full-design: 71.28 Wh energy-rate: 26.561 W voltage: 12.4 V percentage: 97.1831% capacity: 100% technology: lithium-ion I also looked at ACPI data: root@malou-laptop:/home/liv# cat /proc/acpi/battery/BAT0/info present: yes design capacity: 71280 mWh last full capacity: 72420 mWh battery technology: rechargeable design voltage: 10800 mV design capacity warning: 3621 mWh design capacity low: 200 mWh cycle count: 0 capacity granularity 1: 1 mWh capacity granularity 2: 1 mWh model number: 92P1137 serial number: 885 battery type: LION OEM info: SANYO root@malou-laptop:/home/liv# cat /proc/acpi/battery/BAT0/state present: yes capacity state: ok charging state: charged present rate: 0 mW remaining capacity: 70380 mWh present voltage: 12400 mV But I cannot pinpoint anything suspicious: the design capacity and last full capacity seem healthy to me. So is there some other utility that could indicate whether the battery is working as expected, or needs replaced?