AGM: "absorbed glass mat", batteries feature fiberglass mesh between the battery plates which serves to contain the electrolyte.
The thinner grid design in Thin Plate Pure Lead (TPPL) batteries is made possible by a patented process of cold rolled pure-lead grid manufacturing techniques. This process allows more plates to be packaged in the same space than with traditional book mold technology. Separating those thin plates with a porous micro-fiberglass separator and packing them tightly together provides mechanical support for the pure-lead grids and helps increase capacity because of better utilization of active material. The TPPL technology allows for more surface area within a battery, which creates a much more power dense environment that reduces the need for additional battery compartment space while maintaining a longer operational life.
A VRLA battery (valve-regulated lead-acid battery), more commonly known as a sealed battery or maintenance free battery, is a type of lead-acid rechargeable battery. Due to their construction, they can be mounted in any orientation, and do not require constant maintenance. The term "maintenance free" is a misnomer as VRLA batteries still require cleaning and regular functional testing. VRLA batteries have been shown to reach catastrophic failure and are prone to thermal runaway. A common cause of failure is overheating and dust obstructing the valve, preventing release of gasses. They are widely used in large portable electrical devices, off-grid power systems and similar roles, where large amounts of storage are needed at a lower cost than other low-maintenance technologies like lithium-ion.
There are two primary types of VRLA batteries, gel cells and AGM. Gel cells add silica dust to the electrolyte, forming a thick putty-like gel. These are sometimes referred to as "silicone batteries". AGM, short for "absorbed glass mat", batteries feature fiberglass mesh between the battery plates which serves to contain the electrolyte. Both designs offer advantages and disadvantages compared to conventional batteries, as well as each other.