There are certain steps to checking proper battery voltage that not everyone is aware of.
After running the car, turn on your high beams for 1 minute to get the surface charge off the battery, then check the battery voltage, this reading will give you the TRUE and ACTUAL battery condition.
Also, theres a way to check parasitic load (Load in which is still using battery power after the key is in the off position)
http://flashoffroad.com/electr...n.pdf
Read this cause it will give you a list of parasitic loads and ways to check whats causing the load.