Have doubts about your battery and are leery of going to a parts store to have it checked as they may try to sell you one when yours is OK. A second opinion in some cases may have the same result after all it is there job to sell parts. Take your volt meter and with the caps removed (not all battery caps may be removal) and a fully charged battery, at least 12.9-13.2 volts. Start at the positive end and the positive probe into the first cell and the negative into the second should read 2.2 volts keep moving on towards the negative moving both probes one cell and at the end go to the negative post. Not a fool proof method but at least it will give you a starting point. You can also ,key on engine off, turn on all lights, AC fan on high (I do not recommend turning on wipers as this may scratch your windshield) radio and then check it again with a load. The voltage is not as important as there should be no difference between the cells. If there is then go for the full load test and explain to the parts person that you have already performed a cell test but don’t divulge the results it may help keep them honest