What Is A Lead Acid Battery?
Lead acid batteries are electrochemical energy storage devices using lead dioxide (PbO₂) and sponge lead (Pb) electrodes submerged in sulfuric acid electrolyte. Invented in 1859 by Gaston Planté, they remain widely used for automotive starting, lighting, and ignition (SLI), backup power systems, and industrial applications due to low cost, high surge currents, and recyclability. However, they’re heavier and have lower energy density (30–50 Wh/kg) than lithium-ion alternatives.
What are the core components of lead acid batteries?
A lead acid battery comprises lead plates, sulfuric acid electrolyte, and polyethylene separators. Positive plates use PbO₂, negatives use porous Pb, while the electrolyte (H₂SO₄) facilitates ion transfer. Absorbent Glass Mat (AGM) variants replace liquid electrolyte with fiberglass mats.
Internally, each cell delivers ~2.1V, with six cells series-connected for 12V systems. Plate thickness dictates capacity—thicker plates in deep-cycle batteries endure repeated discharges. Pro Tip: Always wear PPE when handling electrolyte—sulfuric acid causes severe burns. For example, a car battery uses thin plates for high cranking amps, while golf cart batteries prioritize thick plates for cycle life.
How do lead acid batteries chemically operate?
Discharge converts PbO₂ and Pb into lead sulfate (PbSO₄) and water, releasing electrons. Charging reverses this via external voltage. Efficiency drops at high currents due to peukert effect—exponential capacity loss beyond C/20 rates.
Practically speaking, a 100Ah battery delivers 5A for 20h but only 80Ah at 20A. Pro Tip: Equalize flooded batteries monthly to prevent stratification—layered electrolyte acidity. For instance, forklift batteries use daily equalization to maintain 1.265 specific gravity.
| State | Positive Plate | Negative Plate |
|---|---|---|
| Discharged | PbSO₄ | PbSO₄ |
| Charged | PbO₂ | Pb |
What are flooded vs. sealed lead acid variants?
Flooded batteries require periodic watering to replenish electrolyte lost via gassing. AGM and gel batteries are sealed, recombination oxygen/hydrogen internally. AGM offers 3x faster charging and vibration resistance.
However, gel batteries suffer from premature aging if charged above 14.1V (12V system). Pro Tip: Use AGM for RVs—they handle irregular charging better. For example, telecom backup systems use flooded types for cost, while motorcycles prefer AGM for maintenance-free operation.
| Type | Maintenance | Lifespan |
|---|---|---|
| Flooded | High | 4–6 years |
| AGM | None | 6–8 years |
How to maintain lead acid batteries effectively?
Check electrolyte monthly in flooded types, topping up with distilled water. Clean terminals to prevent corrosion—apply anti-oxidant grease. Store at full charge; 25°C self-discharge is ~3–4% monthly.
Beyond basic care, use temperature-compensated charging: reduce voltage by 0.03V/°C above 25°C. Pro Tip: Load test annually—healthy 12V batteries should hold ≥9.6V under 50% load for 15 seconds. For example, solar setups often fail due to chronic undercharging—a 30% state-of-charge causes rapid sulfation.
Why choose lead acid over lithium-ion?
Lead acid dominates where cost-per-cycle and recyclability matter. They’re 60% cheaper upfront than LiFePO4. Recycling recovers 99% lead, versus 50% in lithium.
But what about weight? A 100Ah AGM weighs ~30kg vs. 15kg for lithium. However, cold weather performance favors lead acid—they deliver 70% capacity at -20°C vs. lithium’s 50%. Pro Tip: Use AGM in off-grid systems—they handle partial charging better than flooded.
Battery Expert Insight
FAQs
No—older batteries drag new ones into imbalance, accelerating failure. Replace entire banks simultaneously.
Are lead acid batteries recyclable?
Yes—98% of lead is reclaimed. Return spent units to certified recyclers to avoid environmental penalties.
How long do AGM batteries last?
6–8 years with proper charging. Avoid exceeding 14.4V (12V system) to prevent dry-out from over-recombination.