Hey Scotty,
My sister owns a 2014 GMC Yukon Denali XL and I decided to test her battery because she was having some problems with her old battery and had recently replaced it. Her new battery is only 2 months old and I tested it using the TopDon tester you recommended on Amazon. The tester has worked great on my other cars, and I thought it was odd that it was saying her 2 month old battery was already at a 75% State of Health. I also ran the charging test and it indicated "overcharging." Then I used a voltmeter and it showed around 15 volts at idle. I assumed the alternator was bad. So she took it in to a GMC dealer hoping her extended warranty would cover it. The dealer said they found "no problem" and charged her a $180 diagnostic fee. What do you think about this? Would love to know your thoughts, especially given GM's reputation for electrical bugs.
Thanks so much! Appreciate all you do!
The NEW GM charge system is unlike the older ones nor the conventional one. As an overview..the charge system never wants to exceed 75% of battery capacity to prevent over charge and thus the benefits is a longer lasting battery..some say maybe 8 years.
https://ricksfreeautorepairadvice.com/gm-charging-system-problems/
15V is normal . The TopDon tester sounds reeeeeeally dodgy to me.
If the car works fine, then keep on truckin.
Modern GM charging systems can reach almost 16V depending on load and conditions.
15 V is too much. Your alternator is overcharging the battery and the main cause of the battery issue.
