2004 GMC Envoy XUV six cylinder
I have reason to believe my battery is bad. Although it is only about a year old, it recently began having trouble holding a charge. So, to determine it was not due to a short within my vehicle, I did some tests with the battery disconnected. I fully charged it with a 3 amp charger. After waiting 24 hours for the surface charge to go away, I checked the voltage at 12.6. Over next four days, the voltage indicated 12.53, 12.48, 12.45 and 12.42 respectively. According to my research, 12.42 volts is approximately 72% charge. I repeated this test two more times over a two week period, all with the battery disconnected. Each time, the voltage would gradually drop over a four day period and then stabilize at around 12.42 volts. According to the shop where the battery was purchased, the test they performed indicated the battery is good. Any thoughts on this?