Is SLA the same as AGM?

Not exactly. SLA (Sealed Lead Acid) is the general category that includes BOTH AGM and Gel batteries. AGM is one specific type of SLA battery that uses absorbed glass mat technology. When people say "SLA battery" without specifying, they usually mean AGM — since AGM accounts for over 80% of all sealed lead-acid batteries sold. The terms SLA and VRLA (Valve Regulated Lead Acid) are interchangeable.

Which lasts longer, AGM or Gel?

Gel batteries generally last longer than AGM in cycling applications — 1,500+ cycles at 80% DOD for gel versus 200-400 cycles for AGM. In standby/float applications (like UPS), gel also edges ahead with 8-15 year design life versus 5-12 years for AGM. However, AGM batteries have been catching up with enhanced formulations, and the cost per cycle often favors AGM for moderate-duty applications.

Can I use a gel charger for an AGM battery?

A gel charger CAN charge an AGM battery safely — the gel charge voltage (14.0-14.2V) is within the safe range for AGM. However, the lower voltage means slower and potentially incomplete charging. AGM batteries perform optimally at 14.4-14.7V charge voltage. Using a gel charger long-term will result in slight undercharging and gradual sulfation. For best results, use a charger with a dedicated AGM setting.

Why do UPS systems use AGM instead of Gel batteries?

Three reasons: (1) AGM has lower internal resistance, delivering 15-20% more power per kilogram during the high-current, short-duration discharges typical in UPS applications. (2) AGM recharges faster (0.25C vs 0.15C), important because the battery must be ready for the next power outage quickly. (3) AGM costs 20-30% less than gel at equivalent capacity — a significant factor when deploying hundreds of batteries across a data center.

What does "SLA" stand for on a battery?

SLA stands for Sealed Lead Acid. It indicates a lead-acid battery that is sealed with a one-way pressure valve, does not require water maintenance, and can be operated in any orientation without spilling. SLA batteries are also called VRLA (Valve Regulated Lead Acid) batteries. The two main types of SLA/VRLA batteries are AGM (Absorbed Glass Mat) and Gel.

SLA vs AGM vs Gel Battery: What Is the Difference? Complete Comparison

Quick Answer: SLA, AGM, and Gel Are All Sealed Lead-Acid Batteries

SLA (Sealed Lead Acid) is the umbrella term for any lead-acid battery that is sealed and maintenance-free. **AGM and Gel are the two types of SLA batteries** — they differ in how the electrolyte is immobilized.

- **SLA** = Sealed Lead Acid = the category (also called VRLA, Valve Regulated Lead Acid) - **AGM** = Absorbed Glass Mat = electrolyte absorbed in fiberglass mats - **Gel** = Gelled Electrolyte = electrolyte mixed with fumed silica to form a gel

If someone asks you to buy an "SLA battery," they typically mean an AGM battery — AGM accounts for over 80% of all SLA batteries sold worldwide.

What Is an SLA Battery?

SLA (Sealed Lead Acid) battery is a general term for any lead-acid battery that is sealed with a pressure-relief valve. Unlike traditional flooded (wet-cell) batteries, SLA batteries:

- Do not require water addition (maintenance-free) - Can be operated in any orientation (no liquid to spill) - Emit minimal gas under normal conditions (sealed with one-way valve) - Are classified as "non-spillable" for shipping (IATA/DOT exempt from hazmat in most cases)

The term **VRLA (Valve Regulated Lead Acid)** is technically more accurate — the battery is not truly "sealed" but has a pressure-relief valve that opens at 10-40 kPa to prevent explosion in case of overcharging.

AGM vs Gel: The Two Types of SLA/VRLA Batteries

AGM (Absorbed Glass Mat) Batteries

AGM batteries immobilize the electrolyte using a **fiberglass mat separator** between the plates. The mat absorbs approximately 95% of the sulfuric acid through capillary action.

Advantages of AGM: - Lower internal resistance → better high-rate discharge (ideal for UPS) - Faster recharging → accepts charge current up to 0.25C - Lower cost than gel batteries (20-30% less at equivalent capacity) - Better performance in standby/float applications

Limitations of AGM: - Less tolerant of deep cycling than gel - More sensitive to overcharging - Shorter cycle life at high depths of discharge

Gel Batteries

Gel batteries mix the sulfuric acid electrolyte with **fumed silica (SiO₂)** to create a thick, paste-like gel that fills the entire cell.

Advantages of Gel: - Superior deep cycle performance → 1,500+ cycles at 80% DOD - Better heat dissipation (gel conducts heat better than air gaps in AGM) - No acid stratification → uniform plate usage - Longer cycle life in solar/renewable energy applications

Limitations of Gel: - Higher internal resistance → less suitable for high-rate UPS discharge - Slower charging → maximum 0.15C charge current - Higher cost → 30-50% more than AGM at equivalent capacity - Sensitive to charging voltage (must not exceed 14.1V for 12V batteries)

SLA vs AGM vs Gel: Comparison Table

FeatureAGMGelNotes **Technology**Fiberglass mat separatorFumed silica gel electrolyteBoth are SLA/VRLA **Internal resistance**Low (4-8 mΩ/cell)Medium (8-14 mΩ/cell)AGM wins for UPS **Float life**5-12 years8-15 yearsGel wins for longevity **Cycle life (50% DOD)**500-1,200 cycles800-1,500 cyclesGel wins for cycling **Cycle life (80% DOD)**200-400 cycles500-1,200 cyclesGel far superior **Max charge current**0.25C0.15CAGM charges faster **Float voltage (12V)**13.5-13.8V13.5-13.8VSimilar **Charge voltage (12V)**14.4-14.7V14.0-14.2VGel needs lower voltage **Self-discharge**1-3%/month1-2%/monthGel slightly better **Temperature tolerance**-20°C to +50°C-20°C to +55°CGel slightly better **High-rate discharge**ExcellentGoodAGM delivers more watts/kg **Deep discharge recovery**GoodExcellentGel tolerates abuse better **Cost (OEM per Ah)**$1.50-$3.50$2.50-$5.00AGM is more affordable **Best application**UPS, telecom, emergencySolar, cycling, harsh environmentsChoose by application

How to Choose: Application Guide

Choose AGM When:

- **UPS / backup power** — AGM's low internal resistance delivers more power during short, high-current discharge events - **Telecom base stations** — AGM's lower cost and reliable standby performance make it the industry standard - **Data centers** — AGM's fast recharge and high-rate capability match UPS requirements - **Emergency lighting** — AGM's long float life (5-12 years) and compact size fit building safety systems - **Fire alarm systems** — AGM meets UL and NFPA requirements for sealed, maintenance-free standby batteries

Choose Gel When:

- **Solar / renewable energy storage** — Gel's deep cycle capability (1,500+ cycles at 80% DOD) handles daily cycling - **Electric vehicles / golf carts** — Gel's tolerance for deep discharge extends service life - **Hot climates (>35°C ambient)** — Gel dissipates heat better than AGM - **Marine / offshore** — Gel's vibration resistance and deep cycle performance suit marine applications - **Cycling applications requiring maximum lifespan** — Gel costs more but delivers 2-3× the cycle life of AGM at deep DOD

The Naradex Product Range

ApplicationRecommended ProductType UPS backup (5-30 min runtime)[ND12 Series](/products/12v-agm-battery/)AGM Telecom base stations[ND12 / NL2 Series](/products/2v-stationary-battery/)AGM Solar energy storage[OPzV2 Series](/products/opzv-tubular-gel-battery/)Gel (tubular) Long-life standby (10+ years)[NL2 Series](/products/2v-stationary-battery/)AGM (long-life)

Related Resources

- [AGM vs Lead Acid Battery](/blog/agm-vs-lead-acid-battery-difference/) — AGM compared to traditional flooded batteries - [AGM vs Gel Battery for UPS](/blog/agm-vs-gel-battery-which-is-better-for-ups/) — Detailed UPS-focused comparison - [How to Charge AGM Batteries](/blog/how-to-charge-agm-battery-voltage-guide/) — Correct charging voltages and methods - [VRLA Battery Maintenance Guide](/blog/vrla-battery-maintenance-guide/) — Extend your battery's life