Q: 2010 Chevy Traverse starting

If the starter is failing to disengage, that is typically a starter or starter circuit problem. The status the battery would be irrelevant and if the mechanic claims an "overcharged" battery is causing the starter to "run on", I would look for a more competent mechanic. As far as the alleged overcharging of the battery, the output of the alternator has to be measured and compared against the factory specifications in the service manual before you can determine what, if anything, needs to be done.

If the engine is not starting as readily as it used to (or should), there is something wrong. There are many causes of hard starting but illustrative ones are a faulty engine coolant temperature switch (sensor), worn spark plugs, inadequate fuel delivery or pressure (e.g., clogged fuel filter), dirty fuel injectors, contaminated or old gasoline, malfunctioning idle air control valve, poor engine compression, and so forth. You have the specific cause of the hard starting identified if you request a hard starting diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.