AGM vs. Lithium: The Definitive Engineering Comparison
The decision between Absorbent Glass Mat (AGM) and Lithium (specifically LiFePO4) architecture is the most critical turning point when designing a marine, RV, or commercial fleet energy system. Here is the unvarnished engineering reality.
1. Depth of Discharge (DoD) & Cycle Life
AGM: Traditional high-end AGM batteries offer an excellent lifespan, provided they are not regularly discharged below 50% of their total capacity. Pushing an AGM to 80% or 100% DoD repeatedly will severely degrade the lead plates, dropping cycle life from ~1000 cycles down to ~300.
Lithium: Lithium systems thrive on deep cycling. A standard LiFePO4 battery can be discharged to 80% or even 100% DoD safely, delivering upwards of 3,000 to 5,000 cycles without significant degradation.
2. Weight and Energy Density
Lead is heavy. A standard 100Ah AGM battery weighs roughly 65-70 lbs. Because you can only use 50% of that capacity safely, you are carrying 70 lbs for 50 usable Amp Hours. A comparable 100Ah Lithium battery weighs approximately 25-30 lbs, and you can use nearly all 100 Amp Hours. This weight reduction is a game-changer for marine and RV applications.
The Raya Energy Verdict
If your application operates in extreme sub-zero temperatures (below freezing) and primarily requires massive starting power (Cold Cranking Amps), AGM is still the undisputed champion. However, if your goal is long-term, deep-cycle energy storage (like a solar setup or house battery bank) where weight is a factor, Lithium justifies its higher upfront cost.