How long are you leaving the A2 on the charger? MTL you may have "overcharged" the battery, overloading the memory in the battery itself, therefore resulting in less usage time from a "fully charged" battery.
Typically, as a sales rep, I recommend my customers only charge their phone for the full 4-8 hours, when it is the FIRST time they charge their phone. typically after that, it takes only 2-2.5 hours to provide the phone with a full charge. Over charging will fry the memory and make the battery hold less charge and over a period of time eventually kill the battery, making you have to buy a new one.
P.S. If I am completely off base please let me know. Yes I am noob, but this info was actually part of my training courses so I'd love to tell them they're wrong. Hope I was helpful.