While there are several battery construction methods, AGM and lead-acid batteries are the two most common. Here are the differences:

Absorbed Glass Mat (AGM) Battery

• 4Growing in popularity (especially with start/stop vehicles)
• Been around since 1980s
• Better for high vibration and extreme cold conditions
• Non-spillable
• Charging: more complex than lead-acid. If the AGM battery is more than 50% discharged, special procedures are involved. AGM batteries prefer charging at voltages below 14.0v. Use a charger with an AGM setting 

Lead-Acid “Wet Cell” Battery

• Most popular
• Been around since 1859
• Must remain upright (can leak)
• Charging: requires training plus a battery charger with microprocessor control of the charging process

NOTE: Due to the sulfuric acid in the electrolyte, the lead-acid battery is prone to sulfur coating.