Understanding The Types Of Lead-Acid Batteries May 17, 2016
The Difference Between Wet, Gel, AGM And EFB Batteries
Often different chemistries of a lead-acid battery are confused as a separate technology altogether. However, the majority of batteries found in most modern day vehicles are lead-acid, including AGM. Absorbent Glass Mat (AGM) batteries, along with Flooded (or Wet Cell), Gel Cell, and Enhanced Flooded Batteries (EFB) are sub-sets of lead-acid technology. Just as Lithium Cobalt Oxide, Lithium Manganese Oxide, Lithium Nickel Manganese Cobalt Oxide, and Lithium Iron Phosphate are all sub-sets of lithium-ion batteries. Each subset of lead-acid batteries classified into two main groups: Flooded and Valve Regulated Lead-Acid (VRLA), which is also known as Sealed Lead-Acid (SLA). Below we will explore the differences between each technology.
Flooded (Wet Cell)
Type: Flooded
Cycle Life: 250-500 Cycles
Duty Cycle: 50% DOD
Typical Charging Voltage: 14.4-14.5 Volts
Flooded or Wet Cell batteries are the most common and economical lead-acid chemistry. Flooded batteries have a liquid electrolyte solution (hence, “wet”), which requires maintenance after charging and discharging cycles. Most Flooded batteries will require regular maintenance of its electrolyte every 3-6 months. If a Flooded battery is accidentally overcharged, additional electrolytes can be added to the battery, making it more resistant to improper charging. However, Flooded batteries experience substantial reduction in battery life if discharged below 50-percent depth-of- discharge. Care must be taken to avoid coming in contact with the battery acid, and must be installed in the vertical position.
Enhanced Flooded Battery (EFB)
Type: Sealed Lead Acid (SLA)
Cycle Life: 500-1000 Cycles
Duty Cycle: 60% DOD
Typical Charging Voltage: 14.4-14.5 Volts
Enhanced Flooded Batteries are an economical battery used in micro-hybrid vehicles that are designed to withstand the cyclic demands of start-stop vehicles. EFB batteries are similar to Flooded batteries as it has a liquid electrolyte solution, but designed to handle two times higher cycling endurance and roughly a 16-precent increase in duty cycle. Despite its increased performance for start-stop applications, EFB batteries are charged similar to standard Flooded batteries, and installed in the vertical position.
Gel Cell
Maintenance: Maintenance-Free
Type: Sealed Lead Acid (SLA)
Cycle Life: 300-500 Cycles
Duty Cycle: 50% DOD
Typical Charging Voltage: 14.2-14.3 Volts
Gel Cell batteries were developed to create a non-spillable version of a Flooded battery. Internally, they are similar, except that the antimony in the lead plates is replaced by calcium and its electrolyte is combined with fumed silica to produce an immobilized solution. Unlike Flooded batteries, Gel Cell batteries can be mounted in almost any position. They have less electrolyte evaporation, an increased cycle life, and more resistance to shock, vibration and acid stratification. Although Gel Cell batteries are still found commercially, they have limited application of use due because of advancements in Absorbent Glass Mat (AGM) batteries.
Absorbent Glass Mat (AGM)
Type: Sealed Lead Acid (SLA)
Cycle Life: 400-600 Cycles
Duty Cycle: 80% DOD
Typical Charging Voltage: 14.7-14.8 Volts
Absorbent Glass Mat (AGM) represent the latest technology of non-spillable batteries. Instead of using a gelling agent, AGM batteries uses a fiberglass-like separator that absorbs the electrolyte in place. As a result, AGM batteries performance better than Flooded and Gel Cell batteries because they have a low internal resistance (which allows it to deliver higher currents), charge up to five times faster, and cycle down to 80-percent depth-of-discharge. Like all Sealed Lead-Acid batteries, AGM batteries are sensitive to improper charging.
Advanced Absorbent Glass Mat (AGM+)
Type: Sealed Lead Acid (SLA)
Cycle Life: 800-1,200 Cycles
Duty Cycle: 80% DOD
Typical Charging Voltage: 15.2-15.3 Volts
Advanced AGM, or AGM+ batteries are similar to traditional AGM batteries, but have even higher cycling endorse and lower internal resistance, making these types of batteries the ideal battery for micro-hybrid, start-stop vehicles.
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