Vehicle batteries come in many shapes and sizes. More recently they also come in different types.

AGM ( Absorbed Glass Mat) batteries offer several advantages for modern vehicle. They will tolerate being discharged below 50% without degrading much better then standard Lead Acid Batteries. They can be charged much faster

With most new technologies. There comes a price. AGM batteries are, for the moment, much more costly than Lead Acid

Don’t be tempted to substitute a standard lead acid battery. In many cases it will fit, however, at best the battery will be damaged by incorrect charging and in worst case you will damage the alternator or charging system

AGM batteries recharge faster than regular batteries.

Fiberglass mesh mats soaked in electrolyte carry current faster than liquid electrolyte. Yes, that’s how AGM batteries can deliver big bursts of power even if they’re drained. It’s also how AGM batteries recharge faster than regular batteries. That low internal resistance means AGM batteries can give more amps and accept more amps when they recharge.

Standard batteries need more voltage than AGM batteries to recharge because regular batteries have higher internal resistance. To keep them from overheating, they can only take a few amps at a time at that high voltage.

This means AGM batteries need a special AGM charger. They can take a lot of amps in a short period of time — but an AGM battery charger must keep its voltage lower than 14 volts to avoid ruining the AGM battery. AGM batteries are 12 volts, like all car batteries, and can handle some higher voltage, but only up to a certain point. If a car alternator charges an AGM battery with a voltage higher than 15 volts, it can damage an AGM. It’s not likely, but voltage fluctuations are a possibility.

Credit to Inter State Batteries Home Page