Weird Battery charge problem
 

Just to give everyone some data before hand to hopefully help with my problem.

Car: 2004 Honda Civic Hybrid
Mileage: 170,000
Indicator Lights on: Mant. Required, Check Engine, IMA
Mileage: 38+- (I believe this is due to my Michelin Harmony tires which I have read drop the MPG significantly)

I know that I have probably gotten a good bit more out of my IMA battery than most (replacing at 75k sounds crazy to me) and I have been putting off the change until I can afford it. Here is the problem. Every since I bought the car, when I turn it off, the fan engages and cools/uses battery power til the gauge reads around 50%. Just recently, there is no more fan when I turn the car off and the battery gauge is reading 75%+ all the time now... even when I start the car. Also, there is weird sounding intermittent vibration when I drive which started about the same time so I think they are linked but I could be wrong (good old Murphy's law) . What concerns me most is that I am overheating the battery and killing it faster than before.

Any legit suggestions (besides breaking down and taking it to the repair shop) would be appreciated!