Types of Lead Acid Batteries

Sealed lead acid batteries are still used today because they are an inexpensive and reliable power source. Over the 160+ years since their invention, they have evolved from simple liquid-filled jars into highly sophisticated, pressurized power systems.

1. Traditional Wet Cell (Flooded) Batteries

Wet cell batteries are the original lead-acid design. They contain liquid sulfuric acid that "floods" the internal lead plates.

• Serviceable (Vented): These feature removable caps. Because they "gas" during charging, the water in the electrolyte evaporates and must be refilled manually. If ignored, the plates dry out and the battery fails.
• Maintenance-Free: These are factory-sealed. While you don't need to add water, they still contain free-flowing liquid and must remain upright to avoid acid spills.
• New for 2026 - EFB (Enhanced Flooded Battery): A modern mid-tier option. These are "beefed-up" flooded batteries used in entry-level start-stop vehicles. They offer better cyclic durability than standard wet cells without the high cost of an AGM.

Safety Warning: All flooded batteries produce Hydrogen gas during heavy charging. They require ventilated storage to prevent the buildup of flammable fumes.

2. Sealed Lead Acid (VRLA) Batteries

The term VRLA stands for Valve Regulated Lead Acid. Unlike wet cells, these are designed to be "recombinant." This means the gases produced during charging are captured and turned back into water inside the battery, so they never need to be refilled.

AGM (Absorbent Glass Mat)

AGM is the most popular "dry" technology in 2026. Instead of liquid sloshing around, the acid is trapped in fine fiberglass mats sandwiched between the plates.

• Performance: They offer the best "cold cranking amps" (starting power) and can charge up to 5x faster than a wet cell.
• Durability: They are highly resistant to vibration and can be installed on their side or at angles without leaking.
• Modern Use: Standard for premium "Start-Stop" vehicles, high-end motorcycles, and critical computer backup (UPS) systems.

Gel Cell

Gel batteries utilize a silica additive that turns the liquid acid into a thick, immobile paste.

• High Heat Resilience: Gel batteries are superior in 2026 for "hot-climate" applications (like solar arrays in the Middle East or Australia) where AGM or Wet cells would dry out and fail.
• The "Death Curve": A Gel battery provides a very flat, stable power output for a long time, but once it reaches its discharge limit, the power drops off almost instantly.
• Best For: Deep-cycle applications like electric wheelchairs, solar storage, and marine electronics.

Comparison Summary: Which Lead Acid Type?

A Note on Replacement

In 2026, you can almost always upgrade from a Wet Cell to an AGM for better performance. However, you should rarely downgrade from an AGM to a Wet Cell, as your device's charging system is likely tuned for the faster intake speeds of the AGM.

AGM batteries, also called dry cell batteries or sealed lead acid batteries, came into wide use in the 1980's because they were lighter and more reliable than wet cell or gel batteries for specific applications. An AGM battery is similar to a wet cell battery, except the electrolyte is being held next to the plates in the fiberglass mats, as opposed to freely flooding the plates. Like gel batteries, this makes the AGM battery spill proof, as the acid is contained within the matting technology. They are more vibration resistant, and can withstand colder temperatures than a typical wet cell battery. They cost a little more, and are sensitive to overcharging, which can make them un-suitable for some applications.

AGM batteries outsell gel batteries. They are less expensive, and they are easier to recharge. They also offer more available power for the size. Gel batteries are more useful in applications where the temperature is hotter and a slower rate of discharge is a priority.