Isolating Starting issue

[Anthonyb]

I have a 2008 GMC 2500HD 6.0 gas. For the last week, when I started the truck, it seems to turn over slower than usual. I figured with the cooler weather the battery was going to need to be replaced soon. Today I added an amp and after working on the truck for a couple of hours, the battery was dead. I only played the radio for maybe 5 minutes, just doing checks as I was buttoning things up. I put my charger on it and it read the battery was very low. After an hour on the charger, I headed down to the auto parts to purchase a new battery and asked them to do a test on my original battery. Well the test came back that my battery is fine. The auto parts guy thought it was the alt, but the test showed it to be okay. I am confident there is no drain due to my recent installation. My question is how accurate are those testers the auto parts stores use? It hooked to the battery, pos. and neg. and had a third clamp that he put around the neg cable, looked like the clamp from a timing light. He also said he thought it was the starter. I think it is probably a cable. Can an OEM gm battery have a bad cell or something to cause it to go dead, then after a brief charge and a 15 minute drive, show to be a good battery when tested? I am keeping jumper cables with me just in case. I still think it is the battery regardless of what the test said. The alt gauge shows it is charging around 13, and when it cranks, the starter sounds like it always has. Any opinions?

[txab]

A good load tester will tell if your battery has any guts left

[gmtech4]

a starter draw test takes 5 minites with the afore mentioned load tester,it can check battery condition,alt output and starter draw ,full system check,,

 

have that done somewhere and you will know,

 

batteries dont give test equip a false reading of being good when they are not,

 

the "parts" guy used a hand held little tester right?

[Anthonyb]

 

 

a starter draw test takes 5 minites with the afore mentioned load tester,it can check battery condition,alt output and starter draw ,full system check,, have that done somewhere and you will know, batteries dont give test equip a false reading of being good when they are not, the "parts" guy used a hand held little tester right?

Yes, It was a handheld no bigger than a sheet of paper. It actually printed out a "test report" that says "Battery meets or exceeds..." Starter test Results, Low cranking amps "Starter amp draw is low with ok starter voltage." Charging system test results "No problem" I know this points to the starter, but I cannot figure how the battery could show almost dead with my charger and after being hooked up for less than an hour and a short drive, it shows no problems and it starts fine. I since drove today and it is starting fine.

[gmtech4]

a decent load tester with a gauge will show a failed battery real fast ,if it goes below 9.6 V ,the battery is done

[tswiczko]

You might want to check your ground and make sure there is no corrosion, make sure your terminals are clean, and have good connections on the alternator.

 

But your 4 year old battery is probably getting weak, check the water level in the battery since you probably haven't done that yet

 

Do a specific gravity test on each individual cell. if one cell is noticeably lower than the others, or they are all low, after it has sat for a day with no use then it is most likely the battery