Written by: Randy Anderson Technical Sales & Training Manager
Lead acid batteries today come in many variations. They are commonly referred to as flooded, AGM, Gel, deep cycle, traction, marine, UPS, tubular plate, maintenance-free, valve regulated, motive power and the list goes on. This article breaks up lead acid batteries into three categories based on the type of electrolyte suspension within the battery.
The first, and oldest, technology would be the good ol’ flooded battery. Flooded batteries have the plates submerged in electrolyte that consists of approximately 35% sulfuric acid and 65% water by volume. The majority of flooded batteries have access caps that can be removed so that water can be added to the cells if the levels become low however there are flooded batteries on the market that are completely maintenance-free as well. Maintenance-free batteries have no access caps because they utilize different alloys in the plates like calcium that reduce the amount of off gassing to prevent electrolyte loss. They often have an elaborate vent trap system built into the top of the cover to trap water that is evaporating.
Flooded batteries are the oldest technology, and because of that, the number of types and sizes available are almost limitless. They range in size from a small motorcycle battery that fits in the palm of your hand to the large 4000lb steelcase varieties designed to operate electric forklifts and underground locomotives. Flooded batteries are made for engine starting, deep cycle, traction, uninterruptable power systems, wheelchairs and mobility, marine and aircraft.
Next in popularity to flooded batteries would be AGM batteries. This acronym stands for Absorbed Glass Mat and refers to the absorbent material that separates the positive and negative plates and contains or holds the electrolyte. In AGM batteries the electrolyte is soaked up in the separators, which makes them a much safer battery to work with, as there is no chance of electrolyte leaving the battery if it is damaged or turned over. Most are also safe for transport by aircraft and do not fall under Dangerous Goods classification which can result in freight savings and transporters do not require special licensing or insurance to handle them. The greatest advantage to AGM however is the fact that they require little to no maintenance and do not off gas under normal operating conditions which means they can be used in sensitive environments and closed compartments such as UPS cabinets.
AGM batteries are much more sensitive to overcharge than traditional flooded batteries so special chargers or voltage limiting chargers are required. These special chargers prevent the battery from building up excessive pressure and vent off gas, which, if this occurs, will cause the battery to dry out and result in premature. AGM batteries are gaining popularity today in engine starting applications but are most commonly found in uninterruptable power systems and environments dangerous gases are not permitted.
Gel batteries like AGM are completely sealed and maintenance free however the electrolyte is in the form of a gel or Jell-O like substance. They are typically more expensive to purchase than AGM batteries because the manufacturing process to get the gel completely dispersed between the plates is more much elaborate. Gel batteries are available in a limited number of sizes and footprints and are more predominate in Europe than North America. Capacity is typically less than a similar size AGM battery due to the fact the sulfuric acid in the Gel electrolyte is slower to react. Like AGM batteries, they are more sensitive when charging and care must be taken to ensure the proper chargers are used; overcharging will result in battery dry out and premature failure. Most Gel batteries are manufactured for deep cycle or traction applications such as electric vehicles, floor scrubbers, wheel chairs and mobility applications and are not normally used for engine starting.
Now you know, 3 types of batteries for many different applications. If you have any questions about this article or any other topic don’t hesitate to contact us.