I'm very interested and I understand what you're saying about battery life depends.... However knowing how old the battery is would be good, also if you just put it in a laptop and run a basic free software like batterycare http://batterycare.net/en/download.html it will tell you how much of the total charge it can still hold.
yeah i could do that, but ill pass. its holds atleast 3 hours no matter what program you use . it will be more or can be less. its a battery. the more programs ect you run, the less time it will hold charge. that's with any battery.