Before discussing deep cycle batteries, it’s important to understand battery basics, such as cycles and depth of discharge (DoD).
A cycle is a full discharge and recharge of a battery. DoD measures the capacity used during discharge, with 100% DoD equaling a full discharge.
State of Charge (SoC) reflects the remaining charge, where 100% DoD corresponds to 0% SoC. A deep discharge occurs when 80% to 100% of the capacity is used.
What Is A Deep Cycle Battery?
A deep cycle battery is designed for continuous deep discharges of 80-100% DoD. High-rate batteries can manage a few deep cycles if discharge and charge rates are strictly followed, but repeated deep cycling may cause them to fail over time. Manufacturers usually recommend not discharging below 45% to extend the battery’s lifespan.
Types of Deep Cycle Battery
There are several types of deep cycle batteries, each with distinct materials, pros, and cons.
Flooded Lead-Acid (FLA)
The flooded lead-acid battery, the oldest type still in use, known as a wet cell with a liquid electrolyte. It requires frequent water additions and must remain upright due to hydrogen gas production. Maintenance is high, involving water addition and cleaning acid residue. Their popularity has declined due to weight and maintenance needs.
Valve Regulated Lead-Acid (VRLA) – Gel and AGM Batteries
These lead-acid batteries use gelled electrolytes or absorbed glass mat, eliminating the need for water additions. They are more expensive than flooded batteries but often have shorter lifespans in demanding applications. They don’t require upright storage and reduce corrosion risks.
Lithium-Ion Batteries
Considered the future of deep cycle batteries, they need no maintenance, can be discharged deeply without damage, and charge quickly. Although their higher initial cost may deter some users, they outlast lead-acid batteries in the long run and offer numerous advantages such as being lightweight and maintaining power throughout discharge cycles.
Deep Cycle Battery Applications
Before selecting a battery, determine what needs to be powered, for how long, how often, and the required power. Deep cycle batteries are suited for cyclic applications where users control when the battery is used.
For instance, a medical cart away from an outlet relies on battery power while unplugged. The nurse or doctor activates it daily, requiring consistent long-term power – a deep discharge use necessitating a deep cycle battery. Similarly, cell phone batteries provide all-day power on a single charge and are used daily. Users typically wait until their phone is fully discharged before recharging (100% DOD/SOC 0%). This consistent demand also requires a deep cycle battery.
Deep cycle technology also applies to marine use, RVs, mobility scooters, electric vehicles, and solar systems.
Conversely, high-rate batteries serve back-up roles in emergencies. For example, elevators use these batteries to deliver energy quickly during power failures but may need replacement before use. A high-rate battery acts as an insurance policy for sudden demands of energy while deep cycle batteries provide reliable everyday performance.
How Long Will A Deep Cycle Battery Last?
The lifespan of a deep cycle battery depends on several factors, with lead-acid batteries being more prone to damage than lithium ones.
Proper maintenance, correct charging and discharging practices can help extend a battery’s life. Lead-acid batteries are negatively impacted by improper watering, over-discharging, over-charging, and under-charging, which significantly reduce their lifespan. On the other hand, lithium batteries do not require watering and are not affected by partial state of charge or under-charging. Many lithium batteries come equipped with a smart Battery Management System (BMS) that enhances battery protection and longevity.
Additionally, higher temperatures accelerate battery degradation.
In terms of average lifespan, lithium iron phosphate batteries typically outlast lead-acid batteries, with over 2000 cycles compared to 200 cycles, respectively. Lithium batteries maintain capacity regardless of discharge rate, making them superior for deep cycling applications. It is important to consider the number of cycles a battery can endure rather than just time to gauge its longevity accurately.
For deep cycle applications where discharge rates exceed 0.1C (what is a c rate?), a lower capacity lithium battery often outperforms an equivalent lead-acid battery. To determine the capabilities of your battery, always refer to the manufacturer’s specifications.
What Deep Cycle Battery Has More Capacity?
Capacity varies significantly between lead-acid and lithium batteries due to their different chemistry. Lithium batteries deliver up to 100% of their rated capacity at any discharge rate, while lead-acid batteries provide less usable energy at higher discharge rates.
Both types lose capacity in cold weather, but lithium performs better. For instance, a lead-acid battery’s capacity drops by up to 50% at 0°C, compared to a 10% loss for lithium iron phosphate batteries.
How to Charge A Deep Cycle Battery
To maximize your deep cycle battery’s life and performance, charge it correctly. Proper charging depends on the battery’s chemistry, voltage, and capacity. Holo Battery offers a guide on how to charge a lithium deep cycle battery. Following this guideline will help ensure your battery lasts longer.
Deep Cycle Batteries vs Starter Batteries
Deep cycle batteries are like marathon runners, providing a steady supply of power for long periods, ideal for powering electronics on boats or RVs. In contrast, starter batteries are like sprinters, discharging high power quickly to start vehicle engines. Dual-purpose batteries combine both capabilities, offering short bursts of power and continuous supply in a single unit.
