Good evening Scotty,

My girlfriend has a 2016 4 door mazda 3 automatic with 82,000 miles.  I have replaced her battery 3 times already with corrosion issues around the battery terminals.  My research online has shown that positive terminal corrosion is due to overcharging (alternator) and negative terminal corrosion is due to undercharging.  Do i need to test the alternator first??  First 2 batteries were mazda dealership batteries, the 3rd battery was an advanced auto parts battery.  What is the root cause of battery corrosion??  I use battery cleaner spray, and clean terminals with brush/baking soda.  The car does not burn oil, runs great otherwise. Thank you for the great videos Scotty. Long time viewer. I have watched every single video that you have made. This world needs more noble, honest, good people like you. God bless.

Fadi Salem