I pulled this off Red's battery clinic.... it has alsways served me well:
Q: How do I know if my pack is fully charged?
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Temperature is the key.. always, always, always! IF THE PACK AIN'T WARM AT THE END OF THE CHARGE ROUTINE, IT AIN'T CHARGED! Note I said 'warm'. Not HOT! Hot is NEVER GOOD at the end of the charge routine.. but warm is OK. If using a temp probe, set it for 10 degrees above AMBIENT. If it's a peak controlled charger and the charger shuts down before the pack is slightly warm to the touch.. IT AIN'T FULLY CHARGED. If it's a timer controlled charger and at the end of the charge period the pack is not warm.. it's NOT fully charged yet! By far and away the biggest reason for low capacity numbers is undercharging.. if you have a 5 gallon pail with only 3 gallons in it, your only gonna get 3 gallons out of it. Engage your brain.. check temperature at the end of the charge routine!
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here is the link.
http://www.hangtimes.com/rcbattery_faq.html