What is a deep cycle RV battery?
A deep cycle RV battery is an energy storage unit engineered for sustained power delivery and regular deep discharges, typically discharging 50-80% of its capacity per cycle. Unlike starter batteries that provide short bursts for ignition, these batteries use robust lead-acid (flooded/AGM) or lithium-ion (LiFePO4/NMC) chemistries to endure hundreds of cycles. They’re optimized for RV applications requiring continuous power for lighting, appliances, and solar systems, with lithium variants offering 2,000-5,000 cycles at 80% depth of discharge (DoD).
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How do deep cycle batteries differ from standard automotive batteries?
Deep cycle variants prioritize capacity retention over cranking amps, using thicker lead plates or lithium electrodes. While car batteries discharge 3-5% per start, RV units tolerate 50-80% DoD without plate sulfation. Lithium models achieve 95% efficiency versus 80% in lead-acid.
Automotive batteries employ thin lead plates for rapid energy release, degrading if discharged below 50%. In contrast, deep cycle designs—whether flooded lead-acid or LiFePO4—use dense active materials. For example, a Group 31 AGM battery delivers 100-120Ah with 600 cycle life at 50% DoD, while equivalent lithium packs provide 200Ah/2,000 cycles. Pro Tip: Never use car batteries for RV house loads—shallow cycling reduces their lifespan by 70%.
| Parameter | Deep Cycle | Starter |
|---|---|---|
| Plate Thickness | 4-6mm | 1-2mm |
| Typical DoD | 50-80% | 3-5% |
| Cycle Life | 200-5,000 | 50-150 |
What chemistries dominate RV deep cycle batteries?
Three primary systems prevail: flooded lead-acid (FLA), AGM, and lithium. FLAs offer affordability ($150-$300 per 100Ah) but demand ventilation and water refills. AGMs provide spill-proof operation with 20% faster charging. Lithium batteries, though 3x pricier upfront, deliver 10x longevity and 50% weight savings.
Lithium iron phosphate (LiFePO4) dominates premium RV markets due to its thermal stability and 3,000-5,000 cycle capability. A 100Ah LiFePO4 battery weighs 13kg versus 30kg for lead-acid equivalents. Charging efficiency reaches 99% compared to 85% in AGMs. Real-world example: A 400Ah lithium bank can power a 12V fridge for 5 days vs 2 days with lead-acid. Pro Tip: Pair lithium batteries with temperature-compensated chargers to prevent cold-weather plating.
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FAQs
Never mix chemistries or ages—even 10% capacity variance causes chronic overcharging/undercharging. Replace all batteries in a bank simultaneously.
How often should I recharge my RV battery?
Recharge lead-acid batteries before 50% DoD (12.1V) and lithium before 20% (12.8V). Monthly full charges prevent stratification in FLA units.