deepcycle

A deep cycle battery, commonly referred to as a deep cycle, is a rechargeable energy storage device designed to deliver a steady amount of current over a long period and to be regularly discharged to a substantial fraction of its capacity. Unlike starter batteries used to crank engines, deep cycle batteries are built to tolerate repeated deep discharges and to provide reliable performance under sustained load.

Common chemistries used for deep cycling include flooded lead-acid (wet), absorbed glass mat (AGM) lead-acid, gelled lead-acid, and lithium iron phosphate (LiFePO4). Lead-acid variants are cost-effective and widely available, while LiFePO4 offers higher cycle life and lighter weight. Each chemistry has different characteristics in terms of energy density, headroom for depth of discharge, maintenance needs, and charging requirements.

Cycle life and depth of discharge (DoD) are key performance factors. For lead-acid deep cycle batteries, life improves with a moderate DoD, often around 50% or less, whereas higher DoDs shorten life. LiFePO4 batteries typically tolerate meaningfully higher DoDs (up to 80%–100% in some designs) and offer substantially longer cycle life, often several thousand cycles. Capacity is specified in ampere-hours (Ah) or watt-hours (Wh).

Applications for deep cycle batteries include off-grid solar and wind systems, recreational vehicles, marine applications, remote sensing, and backup power for telecommunications and UPS systems. Proper charging using chemistry-compatible chargers, temperature compensation, and, for flooded variants, periodic maintenance are essential. Safety considerations include venting of gases with certain chemistries, battery placement for ventilation, and proper disposal or recycling at end of life.