What is the difference between VRLA (Gel or AGM) batteries and traditional wet or flooded batteries?

Wet batteries do not have special pressurized sealing vents, as they do not work on the recombination principle. They contain liquid electrolyte that can spill and cause corrosion if tipped or punctured. Therefore, they are not air transportable without special containers. They cannot be shipped via Express Courier or Parcel Post or used near sensitive electronic equipment. They can only be installed “upright.” Because of the cost in time (man-hours), products (distilled water etc), damaged clothing, and polluted environments when being charged and/or discharged wet batteries may actually end up costing more money over the life of the battery than do high quality VRLA batteries. Some brands of wet or flooded batteries are also marketed and sold as sealed or maintenance free, but they are still flooded cell batteries — not “acid-starved” — and they DO NOT have the same pressurized venting system.

Wet batteries lose capacity and become permanently damaged if:

    * Left in a discharged condition for any length of time, due to sulfation. This is especially true of High or Low Antimony and/or Hybrid types.
    * They are continually over-discharged, due to active material shedding. This is especially true of automotive starting types and “so-called” marine/RV combination cycling/starting batteries now being sold by most manufacturers as cheap alternatives to true cycling batteries.