What comes to mind when you think of the power a battery provides? Maybe it's inserting your key into your vehicle's ignition and then listening to the engine turn over and power on. Or holding the power button on the side of your laptop and watching the screen light up.
A vehicle typically uses a starter battery designed for short bursts of high current, while an RV house battery uses a deep-cycle battery designed to deliver steady power over time.
In this blog, we'll focus on the latter.
Deep Cycle Batteries Vs. Starting Batteries
A "deep cycle" battery can discharge deeply, meaning it can reach a low charge state before needing recharging. It is able to supply electrical power over a long period continuously. Unlike starting batteries optimized for short bursts of high current to start an engine, deep cycle batteries are engineered to endure repeated charging and discharging cycles.
Many applications that require energy to be stored, such as marine vessels, recreational vehicles, and renewable energy systems, utilize deep-cycle batteries.
In an RV, deep-cycle batteries serve as the house battery bank, powering lights, fans, refrigerators, water pumps, inverters, and other everyday loads when you’re not connected to shore power.
But with so many different deep-cycle battery types on the market, what is the best and most long-lasting deep-cycle RV battery? This article looks at lead acid, AGM, and lithium deep-cycle batteries. 
Lead Acid Deep Cycle Batteries
Deep-cycle lead-acid batteries deliver a steady and long-lasting electrical power supply. Although lead acid deep-cycle batteries can endure multiple charge and discharge cycles, it is imperative to avoid fully depleting their charge to 0%, one of lead acid batteries' most significant issues.
Doing this can lead to sulfating, which reduces battery life and performance over time. Regular maintenance ensures lead-acid deep-cycle batteries' optimal lifespan and efficiency. This includes monitoring and adjusting electrolyte levels in flooded lead acid batteries (the most common form of lead acid batteries), providing proper ventilation, and keeping the batteries clean and dry.
While they are inexpensive and widely available for energy needs, deep-cycle lead-acid batteries certainly have their share of cons. Proper recycling and disposal methods are necessary to manage the hazardous lead and sulfuric acid components, which are toxic to our environment. 
AGM Deep Cycle Batteries
An AGM (Absorbent Glass Mat) deep cycle battery is a variant of traditional lead acid deep cycle batteries, but their unique construction sets it apart.
AGM batteries use a design incorporating a fiberglass mat soaked in an electrolyte (a mixture of water and sulfuric acid) between the lead plates. The fiberglass mat is a separator and absorbs the electrolyte, immobilizing it to prevent spilling even if the battery is damaged or tipped.
These batteries exhibit a slightly lower energy density than other battery technologies. This means they may have a somewhat lower capacity for their size and weight, which is a concern for applications where maximizing energy storage in a limited space is critical. AGM batteries generally have a higher price tag than traditional flooded lead-acid batteries.
Like all lead-acid batteries, AGM batteries may experience gradual capacity degradation over time. Frequent deep discharges or exposure to harsh conditions can accelerate this degradation process. AGM batteries do not require watering like flooded lead-acid batteries, but they still need proper charging, storage, and temperature management to reach their expected lifespan.
When considering AGM deep-cycle batteries, it's important to note that they have benefits and many drawbacks depending on the application's specific needs. While the higher cost and slightly lower energy density may be limiting factors in some instances, proper care and attention to charging practices and environmental conditions can help.
The Many Uses of Lithium Deep Cycle Batteries
Lithium deep-cycle batteries have transformed the world of energy storage, offering many advantages over traditional battery technologies.
For RV and off-grid use, LiFePO4 batteries also offer a strong safety foundation because they pair stable lithium iron phosphate chemistry with built-in electronics designed to protect against unsafe voltage, current, and temperature conditions.
These batteries provide long-lasting and reliable power, making them a top choice for users. Deep-cycle lithium batteries are pivotal in efficiently storing excess energy generated from solar panels and wind turbines in renewable energy systems. This ensures a consistent power supply, even when renewable sources are not actively producing electricity (when the sun isn't shining or the wind isn't blowing).
The Benefits of Lithium Batteries
Deep cycle lithium batteries are lightweight and compact, boasting an energy-to-weight ratio that tops all other traditional battery technologies. This is highly advantageous in weight and space-critical applications, allowing easy integration into various devices and systems without compromising performance.
The high energy density of lithium deep cycle batteries will enable them to store a substantial amount of energy within a compact package, maximizing energy storage capabilities and extending run times. This efficiency ensures extended operational hours and increased efficiency.
Many LiFePO4 batteries are designed to simplify replacement of lead-acid batteries, but RVers should still confirm charger settings, alternator protection, wiring, fusing, and inverter compatibility.
Lithium batteries also have fast-charging capabilities, allowing quicker charging than the alternatives and leading to reduced downtime. This feature is particularly valuable for time-sensitive applications with quick recharge. This is especially valuable for RVers who recharge from solar, shore power, generators, or a properly installed alternator charging system. 
How Long Can You Expect Deep Cycle Lithium Batteries to Last?
Lithium deep cycle batteries can endure multiple cycles of charging and discharging without experiencing a significant reduction in their capacity.
⚡️ Battle Born Batteries are designed for long-term use and can last up to 10 times longer than lead acid batteries, with 3,000-5,000 deep discharge cycles.
Actual battery lifespan depends on how the battery is used, charged, stored, and installed. High temperatures, repeated operation outside recommended charge settings, undersized wiring, poor external terminal connections, or poor system design can all shorten battery life. A quality BMS helps protect the cells, but the surrounding electrical system still matters.
Along with their long life expectancy, a sufficient warranty makes them a solid choice for the best RV battery and many other applications. Battle Born’s 10-year limited warranty provides long-term coverage, including 8 years of full replacement protection and 2 additional years of prorated coverage for qualifying batteries sold and shipped within the United States and Canada.
The cost-effectiveness is particularly evident when considering the longer operational lifespan of lithium batteries, making them a more economically viable choice in the long run.
An Analysis of Deep Cycle Lithium Batteries | A Mortons on the Move Study
What most people desire out of their RV batteries is straightforward. People want an RV battery that delivers the energy it promises and functions effectively in diverse temperatures.
Concisely, they want to have the power to turn on their AC when it's hot, turn on their lights when it gets dark, and run their heater when the temperature drops.
While reliability is essential, the best RV battery should be cost-effective over its lifetime. The best RV battery should offer sustained value over a significant period of time.
While deep-cycle lithium batteries might have a higher upfront cost, the price over the long term is much more cost-effective than other technologies. Tom and Cait of Mortons on the Move did an incredible long-term cost analysis of different battery technologies, and the results are exciting.
Test Results | Deep Cycle Battery Performance
The analysis of the deep-cycle batteries yielded compelling insights in their studies.
First, deep cycle lead acid batteries supremely underperformed, even under optimal conditions with low discharge rates. The test cut off the lead acid batteries at the manufacturer's suggested voltages, yet they failed to meet their rated capacities.
In that test, the lithium batteries exceeded their rated capacity across the tested discharge rates. Another noteworthy finding was the cost-effectiveness comparison.
Surprisingly, the more expensive AGM batteries that were tested performed worse in terms of cost per watt-hour. Flooded lead-acid batteries remained the cheapest upfront option, but lithium batteries delivered the lowest lifetime cost when cycle life and usable capacity were factored in.
Cost Analysis | A Winner in Deep Cycle Lithium
Now to the lifetime cost, specifically, of deep-cycle batteries. In the Mortons' study, lithium batteries emerged as the clear winner.
The lifetime cost of lithium batteries is two to six times lower than lead acid batteries. This offers substantial savings in the long run. The Morton's study showed lithium batteries' return on investment (ROI) was much higher than other battery technologies. Over time, the need for replacements decreases, significantly lowering the ownership cost.
The minimal environmental impact of fewer replacements is also a significant plus for lithium batteries. Reduced battery replacements result in less waste generation and a lower ecological burden, contributing to a more sustainable future.
Another essential aspect of the ROI for lithium batteries is their recyclability. Recycling lithium batteries is becoming increasingly prevalent. This fact plays a crucial role in reducing the environmental impact of battery disposal. By recycling lithium batteries, we can recover valuable materials that can be reused. This promotes a circular approach to battery production and waste management. 
What Helps Lithium RV Batteries Last Longer?
Lithium deep-cycle batteries are built for long service life, but system design and use still matter. To get the most from an RV lithium battery bank:
- Use compatible charging equipment
- Avoid charging below freezing unless the battery has a built-in heater or cold-charge protection
- Keep batteries within recommended temperature ranges
- Make sure cables, fuses, and terminal connections are properly sized and installed.
Final Thoughts
Lithium deep-cycle batteries have revolutionized energy storage solutions, offering reliability and efficiency across many applications. The ROI for Battle Born lithium batteries is evident through a longer lifespan and a reduced overall cost. For RVers who camp off-grid, cycle their batteries frequently, or want long-term value, lithium is often the strongest choice.
Embracing lithium batteries is a strategic investment. Making an upgrade offers economic benefits and meets sustainability goals for a greener and more efficient future.
