Hi,My name is Tim,
I will do my best to assist you
from the way you explain,i would think that year old battery is bad,it seems to have a dead cell..
you need to load test the battery with the engine
not running,then load test the charging system with the engine running,,this will determine if the problem is the battery or the alternator..if you dont have a load tester,auto zone and most parts stores will load test these for free
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