Solar charge set up damaging battery?
You have two problems.  


The MPPT charge controller is not charging the battery.
The battery is not reaching 100%  


I would start by giving the battery an Equalizing Charge.  The battery may be okay.

First thing to do is measure the output voltage of the PV while the MPPT is (or should be) charging.  Do this periodically throughout a sunny (or mostly sunny) day.   

What I would be expecting is the voltage to remain fairly constant when there is sufficient sunlight (10:00am to 4:00pm).  I would expect the voltage to be around 13 V.

What happens to the PV voltage when you change the angle of the panel?   

If possible use a shunt resistor to measure the PV current as well.  

With an 80 W panel you may get 3 amps at midday assuming the PV voltage is about 13V.  Typically it will take days to charge the battery. About 20 Ah (250 Wh) per mostly sunny day. 

Check the specs on the MPPT for the minimum PV current.   

What you do next depends upon the results of the above.  I will monitor this post to look for your results. 

What I am testing above is how well the MPPT regulates the PV voltage. The MPPT will decrease the battery charge current when the PV voltage drops below the target PV voltage (typically PV ≈ 13 V). If the PV voltage rises above the target PV voltage the MPPT will increase the charge current.  If the PV voltage is closer to 20 V then it is likely the battery is not being charged.  

If the PV voltages look good then then next step is to monitor the charge current and voltage.  The charge characteristic should look something like this: