WHAT IS AN AGM BATTERY?

Both flooded and AGM batteries contain an electrolyte mixture within the battery comprised of approximately 35% sulfuric acid by volume.

That means approximately 35% of that liquid inside the battery is sulfuric acid. 

Flooded batteries have excess electrolytes or free-flowing electrolytes within the cells that cover the cells, usually by 1/2 to 3/4 inch or cover the plate by 1/2 to 3/4 inch. Additionally, flooded batteries are known for off-gassing during charge and discharge operations.

When the batteries are discharged or charged, they give off hydrogen gas. This hydrogen gas is known to be explosive and corrosive, so care must be taken when working around flooded batteries to ensure no sparks or open flames. It’s also critical to wear the proper safety protective equipment, such as eyeglasses and rubber gloves.  
 
AGM batteries, on the other hand, have all the electrolytes absorbed in their separators.

They have thick absorbent glass mat separators in between the positive and negative plates. There is enough electrolyte in AGM batteries soaked up into those glass mat separators.

This means no free-flow acids sloshing around inside the battery. This also means that the batteries are non-gassing. During regular charging and discharge, the batteries do not emit any off-gas.

AGM batteries have rubber valves in the vent caps that, if there's too much pressure built up it, will allow that pressure to bleed off so that the battery doesn't bulge and want to explode.
 
However, flooded batteries are the least expensive battery technology for vehicles and are widely available. They are a tried-and-true technology.

The downside is they're considered hazardous material or dangerous goods, which means care must be taken when working around them and when shipping these types of batteries.

We must ensure that the proper dangerous goods paperwork is available with the proper certifications for handling them. 

AGM batteries are slightly more expensive. These prices have come down in the last few years, but when it comes to automotive starting batteries, they are becoming more available in the market.

The upside is they're considered non-hazardous material as they don't off-gas during regular charge and discharge operations. There are fewer safety precautions regarding paperwork and handling with AGM batteries.  

For more information on flooded and AGM batteries, watch our video on our YouTube Channel.