What Is A Glass Mat Battery?
AGM (Absorbent Glass Mat) batteries are lead-acid variants using fiberglass separators to hold electrolyte, enabling spill-proof construction and high-current discharge. They’re ideal for deep-cycle applications like solar storage or marine use, offering 3–5x faster recharge than flooded batteries. Charging requires voltage limits of 14.4–14.8V (12V systems) to prevent dry-out. RG72105P Product
How does AGM technology work?
AGM batteries use electrolyte-saturated glass mats between lead plates, eliminating free liquid. This design enhances vibration resistance and permits 2–3x higher discharge rates versus flooded counterparts. Oxygen recombination minimizes water loss, enabling maintenance-free operation.
The fiberglass mats act like electrolyte sponges, with 90–95% pore saturation. During charging, oxygen from positive plates diffuses to negative plates, recombining into water. This closed-loop system prevents gassing except during overcharge. For example, a 100Ah AGM battery can deliver 300A for engine cranking, whereas flooded types struggle beyond 200A. Pro Tip: Use temperature-compensated chargers—AGM’s low internal resistance (2–4mΩ) causes rapid heat buildup during high-current charging.
| Parameter | AGM | Flooded |
|---|---|---|
| Cycle Life @50% DoD | 600–1,200 | 200–500 |
| Charge Acceptance | 0.3C (30A) | 0.1C (10A) |
| Self-Discharge/Month | 1–3% | 4–6% |
What are AGM’s key advantages?
AGM batteries provide maintenance-free operation and superior cold cranking amps (CCA). Their sealed design allows installation in any orientation, perfect for tight RV compartments. With 99% recombination efficiency, they outlast flooded types in partial-state-of-charge scenarios common in solar applications.
Beyond durability, AGM’s low internal resistance enables faster recharges—a 100Ah unit reaches 80% SOC in 4 hours versus 8+ hours for flooded. But what happens if you mix AGM with other battery types? Parallel connections with gel or lead-acid create unequal charge voltages, accelerating degradation. Pro Tip: For solar systems, size AGM banks 20% larger than lithium equivalents—their usable capacity below 50% DoD is limited. Consider our RG72180 Product for high-capacity needs.
Fasta Power Expert Insight
FAQs
Yes—their spill-proof design allows vertical/horizontal mounting. Avoid inverted positions where terminals contact surfaces.
How long do AGM batteries last?
5–7 years with proper charging. Letting them sit below 12V (50% SoC) causes irreversible sulfation, cutting lifespan by 60%.
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