Is my battery toast?

Hey guys i think my true rc 14.8 volt battery is toast.I can charge it on my
hyperion duo,it will take a full charge,each cell is reading 4.20 4.19 4.20 4,18
But when i put it in my losi 8 buggy and pull the trigger the car runs very
slow like it has no power.I check it with a volt meter and it read 16.6 volts.
I check all soldering joint and check my motor,everything is find.I tryed a
different battery,and it seems to work.Then i charged it again and put it
up for a while and check it with the volt meter and each cell was like
this,4.0 3.70 4.16 4.19 i think this batt it toast it was a little puff at one
time i ran it over greared ,temp was about 138.so what do you guys think?