My 12v battery in my 2017 Volt with ~10k miles was recently found to be dead, when my property manager tried to move the car. I called several auto parts stores on my island (Hawaii) and got prices from $190-220 for replacement AGM battery. Most would not change battery, which in retrospect was probably fortunate. I ended up buying it from only Chevy dealer on my island who quoted me a $225 battery cost. They trucked it to their affiliated Toyota dealer (same company owns Toyota and Chevy dealership) on my side of the island where I asked them to install it. I was not on island and could not replace it myself. Upon completion, they told me the bill was ~$525 for replacement. They claim that I was given a gross understatement of the battery cost and the rest was labor. I balked and spoke with manager who agreed to honor the $225 price but my total cost was $319.23 including tax for replacement. Is a charge greater than $500 normal when the dealer replaces the 12v battery?