Deep cycle batteries go by many names. Call them leisure batteries or marine batteries, we’re talking about the same thing. They are an essential part of power storage for numerous applications. From supplying DC power storage for recreational vehicles, boats, and golf carts, to critical backup power and off-grid supply, there is a massive demand for reliable batteries that can withstand the rigorous demands of the user.
Our Top Picks
This deep cycle battery review is going to consider the needs of all buyers. I know RV owners are keen to find the best products to supply power for their recreational needs. Off-grid and hybrid solar installations are becoming increasingly popular and this requires a higher caliber of deep cycle battery. For this type of application, the ability to handle exceptionally deep cycles is of great importance. For critical backup power, deep cycle batteries, used with an inverter can be a life saver and an important aid for businesses that cannot afford a power shutdown, even for a brief period.
Apart from the leisure battery market, backup power is one of the greatest advantages of battery power. After many years in this industry, I understand the value of high-quality deep cycle batteries. At home, or for critical applications, like medical facilities and servers, batteries allow for complete uninterruptable power. In many instances, a backup generator simply won’t cut it. There is a time delay before the generator starts up and this can be detrimental in some cases. I’ve found that deep cycle batteries, a charger and an inverter is the best way to ensure quiet, clean, and constant power during an outage.
Best RV Deep Cycle Battery Review
While this review is essentially aimed helping you find the best RV deep cycle battery, they can also meet the needs of anyone looking for 12V battery power storage. Choosing which is best for a particular application will be explained in the buying guide.
Regardless of your budget, we’ve done some extensive research to find the best, or ultimate deep cycle batteries and options that will be easier on your wallet. The emphasis being on getting the best value for your money. This is true for the cheap batteries and the more expensive ones.
1. Battle Born LiFePO4 Deep Cycle Battery
Many might view the Battle Born LiFePO4 deep cycle battery off as being too expensive. Before you do, perhaps take a look at this review. Spending more on a high quality lithium ion battery can be worth it in the long run, especially if you’re using a solar charger. This is something I’ll be discussing in some detail when we get to the deep cycle battery buying guide. For now, I’ll give you the short version. Lithium ion batteries are the best for erratic charge situations.
Unlike lead acid and gel equivalents, Lithium batteries don’t need to be kept at full charge when not in use. This versatility is of particular value when you don’t have a permanent battery charging setup. Though there’s a lot more to the story than just this, which you can read about later in the article.
I know my batteries, and I’ll say right off the bat, the Battle Born LiFePO4 deep cycle RV battery is nothing short of magnificent. Yes, the price is pretty high, but I’ve seen more expensive lithium ion batteries that don’t impress like this one does. Without getting overly technical, I have to point out that the use Lithium Iron Phosphate (LiFePO4) is the ultimate in safety and high-power delivery, combined with exceptional battery life. If you’re considering lithium ion batteries for your RV, I highly recommend that you read the buying guide to find out more about this technology. Most consumers believe that all 12V lithium batteries are equal. Nothing could be further from the truth. Lithium is the common denominator amongst these batteries, but the other elements are not always the same and this makes a huge difference. For now, trust me when I say LiFePO4 is the best you can get when it comes to battery technology.
Something that impresses me no end is the inclusion of a built-in battery management system (BMS). This is another aspect to lithium batteries that will be covered in the buying guide. Essentially, if you’ve been using lead acid (or gel) deep cycle batteries in your RV, you can’t simply haul out the old battery and replace it with a lithium alternative. The charger could damage your lithium ion battery. This is why I really like the built in BMS in the Battle Born battery. Clever technology prevents the inevitable over charging that would otherwise harm the battery if you’re using a conventional 12V battery charger or power converter.
Now let’s look at that price tag to see if you’re getting any value for your money. The Battle Born LiFePO4 is rated for 3000 – 5000 cycles. After 3000 cycles the battery will still have about 75 – 80% of its original capacity. This means it will remain perfectly usable, even after 3000 cycles. To provide some context, I’ve seen cheap deep cycle batteries that barely reach 1000 cycles, by which time the capacity can be less than 50% compared to when the battery was new. The best AGM batteries may come close to this 3000 – 5000 cycle rating, but I’m pretty sure the capacity loss will be greater. So, when contextualizing the price of this battery consider that it will last 10 – 20 years for pretty rigorous use. I calculate just over 13-years if the battery is fully discharged (±80%) and then recharged every day. For the average RV owner this battery will probably last a lifetime. Sometimes, it’s worth spending big as a once off, if it means never having to replace your RV batteries.
This battery is extremely lightweight for 100AH battery, only 31-pounds. It is completely sealed and perfectly safe. I reckon it’s the safest deep cycle battery you can get. The Battle Born LiFePO4 can also take more punishment that just about any other Li battery. With 100A continuous current and a surge capacity of 200A for up to 30 seconds, with almost unlimited current restriction for 0.5 seconds, this is about as tough as a battery can get. This also makes it safer when it comes to a short circuit or load surge.
As a top quality, US made deep cycle battery, the Battle Born LiFePO4 is phenomenal at any price. I doubt you’ll find better quality. There are more expensive lithium batteries with fancy LCD displays and some pretty cool technology, but these cost a lot more and won’t provide you with a longer battery life. In the context of high-end deep cycle batteries, with an exceptionally long lifespan, this is actually incredible value for money. The 10-year warranty kind of says it all. How many battery manufacturers offer this type of reassurance? Comparing the Battle Born LiFePO4 to the highly publicized and acclaimed Tesla Wall, I think the Battle Born battery is far better value for money.
2. Optima Batteries 12V 8016-103 D34M BlueTop Starting and Deep Cycle Marine Battery
RV and boat owners looking for a top-quality starting battery should pause and take notice. With exceptional cranking and cold cranking capabilities, the Optima D34M BlueTop is the ultimate deep cycle marine battery for heavy-duty engine starting.
A departure from the regular deep cycle batteries in this review, the Optima BlueTop is specifically designed for the heavy discharge associated with starting an engine under tough conditions. Regular cranking power is 750A, with a remarkable cold cranking capacity of 870A.
Even the largest, high-compression RV engine won’t be a challenge for this battery. While the 120 minute reserve capacity is mighty impressive, I wouldn’t recommend this battery for truly deep cycle applications. If you’re looking for a deep cycle battery to run numerous RV accessories, I’d recommend the Optima Yellow Top range. The BlueTop battery is specifically designed for optimum engine starting. The 55Ah capacity is also not that suited for high wattage discharge over a longer time period.
The unconventional design is part of the magic hidden inside this battery. The circular tube shape of the battery cells is not just an eye catcher, it serves a purpose. Optima batteries use a continuous spiral lead cell. Most conventional lead batteries use a series of flat lead plates. This design increases the durability and performance of the battery with incredible effect.
Top quality is furthered through the use of 99.9% lead with a lead oxide coating. In addition to this, it is an Absorbed Glass Mat (AGM) battery, for improved cooling which further extends battery life. The guys at Optima claim that this battery offers up to 3-times more charges than other marine batteries. That’s quite a stretch though. I’m sure it will offer three times as many cycles when compared to really cheap deep cycle batteries. It will probably outperform most AGM batteries, but I doubt that this will be three times the charge cycle of most high-end AGM batteries. This battery is completely spill-proof and has exceptional vibration resistance, up to 15-times more than most others. This another big advantage for boats and RVs.
The Optima 55AH BlueTop marine battery is no run of the mill powerpack. It has a specific design for a specific purpose. This has to be the best heavy-duty starting battery that you can get. At the very least near the top of the pile. To this end, I believe they have pretty much hit their target. The Optima BlueTop is one of the more expensive options, but it is also quite incredible. It costs more to manufacture a spiral lead battery cell to precision tolerances, but the result is worth it. This is obviously a battery manufacturer who is willing to go the extra mile to ensure supreme quality and durability.
3. WindyNation 100 amp-Hour 100AH 12V 12 Volt AGM Deep Cycle Sealed Lead Acid Battery
The first two RV deep cycle batteries in this review are exceptional, probably the very best in their respective categories. Though their price cannot be ignored. I don’t think the average RV owner wants to spend that much. This brings us to the WindyNation 100AH AGM battery. As a solar battery, this is a cost-effective alternative to really expensive offerings. If you’re looking for an above average deep cycle battery for general RV use, this one is a real winner.
The price is perfectly reasonable. The basic quality and life expectancy is way beyond my expectations for this class of battery. This could be seen as one of the best value for money deep cycle batteries and can be used for every application for which a quality deep cycle battery is essential.
Before lithium ion batteries came along, AGM batteries were seen as the best for solar charging. Really, the best type of deep cycle battery, period. Absorbed Glass Mat technology offers superior cooling and reduced coolant loss through evaporation. In addition to improved cooling, the more expensive AGM batteries utilize more lead, which is of a higher quality standard. The WindyNation 100AH deep cycle battery can certainly be ranked among best AGM batteries.
By using 99.95% pure (unrecycled) lead, and plenty of it, this battery has a longer lifespan than most lead acid batteries. Rated cycle life can compare to many of the top-rated lithium ion batteries. Though it doesn’t cost quite as much. The manufacturers specify a 10 – 15 year float life at 25°C (77°). This temperature spec is an important one, as you will learn in the buying guide.
I always judge a lead acid or lead gel battery by its weight. I know lighter weight is preferable for portability. But when it comes to lead, heavier is better. The best lead acid batteries, have thicker, denser lead plates. More lead, means more weight. I’ve noticed the really cheap batteries are much lighter. This usually means poor quality recycled lead. When lead recycling is done on the cheap, there are many impurities. This means a more porous lead plate that corrodes quickly, drastically shortening the battery life. This is why I find the 66-pound weight of the WindyNation battery a great reassurance.
I’ve always felt that quality AGM batteries are the best genuine value. When you compare the WindyNation to standard lead acid batteries, it seems expensive. When you consider that this battery is likely to last twice as long as good quality conventional lead acid batteries, and 3 – 4 times as long as the cheap ones, it really isn’t that expensive. The 1-year warranty is quite normal for this class battery.
5. Mighty Max Battery 12V 100AH Battery for Solar Wind DEEP Cycle
The Mighty Max AGM deep cycle battery is on a par with the WindyNation battery reviewed above. It is equally deserving of the title best value RV deep cycle battery. An AGM battery will always be my first choice when considering a lead acid battery for harsher working conditions, like off-grid homes, or an RV that uses solar panels. Even if you’re using more conventional charging methods, like campsite shore power or a generator, the Mighty Max AGM battery will outlast and outperform cheaper flooded lead acid batteries.
Weighing in at just under 64-pounds, I’m convinced this battery is packed with high-quality, dense lead plates. That’s what I want from the best AGM batteries, plenty of lead. This is what makes it last longer. In addition to this, the AGM format allows for a longer lifespan and improved charging with longer (deeper) cycles.
The Mighty Max brand is well respected and this AGM 100AH deep cycle battery can rank as one of the very best in its class. The price is in line with my general expectations. This being a bit more expensive than conventional lead acid batteries, but with a much longer battery life. You save in the long run. This would be one of my first choices for an affordable solar battery. They offer a one month refund, quality assurance, and a 1-year warranty on this battery.
6. NP6-225Ah 6V AGM Deep Cycle Battery
I’ve noticed some manufacturers prefer using low volt cells, or 6V batteries, instead of a 12V deep cycle battery. In reality, it does not make any difference, you’ll be using two NP6-225AH 6V batteries in series to obtain 12V. I guess the real advantage is the size versatility. Typically, a 6V battery will be half the size of a 12V equivalent with the same AH rating. This allows you to install your batteries in more confined spaces, with differing configurations. In the end, it works just like a 12V battery. Connect any amount of batteries, grouping sets of two in series, and then connecting all the groups in parallel to create multiple 12V battery banks.
The most notable difference between NP6-225AH (Apart from the voltage) and the others is the higher AH rating. Most deep cycle manufacturers offer around 30AH to 100AH batteries. For longer ampere hours, you have to connect more batteries in parallel. The NP6-225AH delivers 225AH, more than double what we would normally expect. This means that a single 6V battery provides more watts per hour than a 12V 100AH battery. You won’t need as many batteries to keep your RV powered up for longer working times.
As far as quality goes, this as good as any of the best AGM batteries reviewed so far. It is a high quality, valve-regulated, lead acid AGM battery. Offering the performance and battery life we would expect for solar and more heavy-duty RV use.
The NP6-225AH is a wonderfully practical RV battery with a 1001 other uses. It is a high-quality product with a 1-year warranty and a 30-day money back guarantee. Though the warranty contains fine print that might apply to some battery buyers. The warranty is limited 6-months for “mobility” applications. The examples given are wheelchairs, scooters, pallet jacks, and golf carts. All these devices are propelled by battery power and this might be what they mean by mobility products, but it’s all a bit vague. After all, an RV is mobile, but this mobility is not powered by the deep cycle batteries. This leads me to believe that, when used for RV power, this battery should be covered by the full 1-year warranty. Though I can’t say with complete certainty.
7. Weize 12V 100AH Deep Cycle AGM SLA VRLA Battery
As a number one best seller on Amazon, the Weize 12V 100AH deep cycle battery may well be the ultimate in excellent value for money. Judging this battery purely on price vs quality, it is a real winner in my book. As accomplished as any of the best AGM lead acid batteries, this one is exceptionally easy on the pocket. The Weize LFP12100 offers all that you’ll get from the other value priced 100AH AGM batteries in this review. This means a longer lifespan, compared to regular flooded lead acid batteries, especially for more rigorous applications like off-grid solar power. The truly maintenance-free aspect of AGM batteries is another reason for their great popularity.
At 57-pounds, this battery is marginally lighter than the other 100AH AGM batteries that we’ve reviewed here. I wouldn’t read much into this weight difference as it’s only a few pounds. All indications are that this is a top-quality battery, manufactured using only the highest grade lead. This is, as I’ve already pointed out, vital to getting the best use from your lead acid deep cycle battery.
By popular opinion, this is the best value for money AGM deep cycle battery available. I have no reason to doubt that you’re get a great deal when buying the Weize AGM 100AH battery. The 1-year warranty is in line with expectations, certainly the market standard for this class of battery.
8. Renogy Deep Cycle AGM Battery 12 Volt 100Ah
The Renogy deep cycle AGM battery is one of those technological wonders. Understandably, the manufacturer isn’t too keen on divulging all the secrets to their formula. Information is a little vague. Using terms like “quinary alloy plates” and “improved electrolyte” may leave the general consumer somewhat bewildered. When I explain battery technology, later in the article, some this technical jargon should make better sense.
Without getting too technical, I want to make it clear this battery is far from ordinary, it’s exceptional. Instead of the normal lead acid reaction, the Renogy deep cycle battery uses a unique alloy, consisting of five different metals. The elements used, appear to be a trade secret, as is the unique electrolyte which is something different to regular battery acid. What I can tell you about quinary alloys used for lead acid batteries is that this a superior type of battery plate. Lead remains the essential metal for generating the electrochemical reaction. Other elements (like bismuth, cadmium, arsenic, and cerium) are added to improve the battery in several ways. Alloys such as these reduce internal resistance and increase discharge currents. The end result is a battery that provides longer discharge times with a higher current capacity. The battery will offer improved performance and a longer battery life. Advanced electrolytes usually means improved current capacity and generally reduced corrosion.
In short, this battery is designed to outlast and outperform all other AGM batteries. The power to weight ratio is also improved. This means the 64-pound Renogy 100AH deep cycle battery is going to offer improved voltage at high discharge, when compared to a regular AGM battery of the same weight. Charge capacity is vastly improved. Few lead acid batteries can safely be charged at more than 20A, smaller batteries can be as low as 10A, whereas the Renogy battery can a handle a 30A charge current, offering the fastest recharge times. Additional advantages include improved discharge at extreme temperatures, rated discharge temperature range is a mind boggling 5°F to 122°F. The effective charging temperatures are also pretty impressive, 5°F - 104°F.
The Renogy 12V 100AH AGM deep cycle battery leaves all others a little lacking on every level. It is one of the more expensive options, but man is this an extraordinary battery. I suppose no one gets too excited about RV batteries, but this one comes close. Renogy is a high-end battery manufacturer, with an exceptional reputation. To this end, they offer an outstanding warranty of 5-years on the 100AH battery and 10-years on 200AH batteries and upwards. Yes, this is an expensive battery, but you’re definitely getting what you pay for.
9. Odyssey PC925 12 V Automotive and LTV Battery
The Odyssey PC925 is a small AGM deep cycle battery. Not quite up to scratch for a large RV, this battery is rated for Light Transport Vehicles (LTV). This could include some smaller RVs, but it’s not on the high end of the scale when it comes to the required AH and cranking power. It could also be a great battery for boats that don’t require heaps of power to start. The main advantage to this battery is its smaller size. It can fit into places where large deep cycle batteries won’t.
Like the Optima battery, reviewed above, the Odyssey is a deep cycle battery designed for vehicle starting, not high-watt long discharge. This battery is rated for 28AH and a cold crank amperage of 330A. Dimensions: 6.6” X 7” X 5”. Because this is a completely sealed AGM battery, it can be mounted in any position and is perfect for vehicles with a small battery compartment.
I have no doubt that is a high-quality battery. Manufactured from high grade pure lead, it has a rated life expectancy of up to 400 cycles (80% max discharge). That should be anything from 4 to 10 years. Reserve capacity is 52-minutes, which is to be expected for a deep cycle battery of this size. Recharge time is exceptional, 4 – 6 hours.
When I started researching customer reviews for this battery, I was surprised to see so many 1-star reviews on Amazon. This was until I started reading the reviews. One after the other, I read of guys who said: “I left the battery for 6-months and then no juice”, or a similar complaint. Most of the negative reviews were after leaving the battery uncharged and unused. These people were annoyed when they did not receive a new battery under warranty, because of misuse. Sorry guys, leaving a deep cycle for 3-months or longer without any maintenance charging is certainly misuse. No battery manufacturer will replace or refund for a battery that has endured this type of treatment. If you’re unaware of this, and other deep cycle battery maintenance issues, I suggest you read further, as this will be discussed in the buying guide.
With the previous statements in mind, I have to say I’m mighty impressed with the 3 and 4-year full replacement warranty that Odyssey offer on this product. If you’re in the market for a small deep cycle battery of an incredibly high quality standard, this one comes highly recommended.
10. VMAXTANKS VMAX V35-857 12 Volt 35AH AGM Battery Marine Deep Cycle HI Performance Battery
We’re ending this review with the very best option for a high discharge marine deep cycle battery. Okay, this is an expensive 35AH battery, but it’s designed to work hard and last an extraordinarily long time. We’ve reviewed quite a few 30 – 40 AH deep cycle AGM batteries already, all quite reasonably priced. The VMAXTANKS V35-857 is in a completely different league and priced accordingly. The lead-calcium alloy plates are tops. This battery will endure incredibly deep cycles and high discharge currents like few others can. If you need a hardworking battery that’s going to last, this one is bound to impress even the most skeptical of critics.
The VMAX V35-857 displays all the hallmarks of an industrial grade AGM battery. It’s tough, reliable and a top performer. Recommended for boats and trolling motors, this exceptional battery will also go above and beyond for a small RV starting battery. We should be aware that this is not a high AH battery and will be limited when powering RV accessories.
No corners have been cut by this US top-quality battery manufacturer. They take pride in their virtually indestructible tanks, and all-round durability of their battery products. You can expect noticeably longer runtimes and a battery that will keep performing well for many years. There’s a certain measure of confidence that one gets buying a quality product like this one.
RV Deep Cycle Battery Buying Guide
When you started out reading this battery review, you may have thought buying the best deep cycle battery for your RV is a simple matter of looking for the best price. It is clear, from the various batteries that we’ve reviewed, that this certainly is not the case. Deep cycle battery prices vary greatly and there are several reasons why one battery can cost more than twice as much as another.
The price difference between the various types of batteries available to you, is not just about brand and marketing. As with all products, some brands are more expensive than others. This is something that is always a matter for debate. Some believe that a cheap product, regardless of where it is made or by whom, is the best choice. I’m not of this opinion. When it comes responsible manufacturing methods, quality control, superior materials, and dependable customer support, some brands shine above the others. Generally speaking, paying a small premium for a trustworthy brand makes better sense.
In sourcing the best deep cycle batteries for this review, we’ve taken brand repute into account. Some may be cheaper than others, but one thing remains constant, we’ve searched for quality and service that offers the best value for money.
Now, even though you may satisfied with the quality of the batteries that we’ve selected for this review, there is quite a difference in the technical specifications. Most are lead acid, some use lead alloys, others are lithium ion batteries. All of them vary in price and this has a lot to do with technical details. Without a good knowledge of deep cycle batteries work, most importantly the materials used in their manufacture, it is not easy to tell if you’re getting the best deep cycle RV battery for your needs.
In this battery buying guide, I’m going to share my knowledge of batteries, based on decades of industry experience. For many years, I was in the business of supplying batteries, inverters, and solar charging equipment. Who better then to advise you on how to go about buying the best deep cycle battery for any situation? Not just for an RV.
What is a Deep Cycle Battery?
A deep cycle battery is a rechargeable battery capable of high discharge rates over a prolonged period of time. A battery cycle is defined by the charge vs discharge. A complete battery cycle is the discharge, by supplying power and the recharge, accepting power.
The key difference between a deep cycle battery is the ability to discharge most of its capacity (up to 80%) before recharging. A rechargeable battery for engine cranking is usually designed for a high current discharge, only utilizing a small percentage of the total charge. Using a high discharge, short cycle battery, for deep cycle applications will damage the battery, shortening its lifespan.
The most common type of deep cycle battery utilizes a lead acid electrochemical reaction. Though there are several types of lead acid batteries, as well as gel and lithium ion batteries. The various types of commercially available deep cycle batteries can be listed as follows:
A Brief History of Battery Technology
Understanding deep cycle batteries has a lot to do with battery chemistry. So, before going into the details of more sophisticated modern rechargeable batteries, it might be informative to start from the very beginning. Gaining an understanding of the basics from history, should make it easier to understand the complexities of modern battery technology.
Batteries are the oldest form of electrical power. It is believed that the ancient Greeks began experimenting with electrochemical reactions around 2000 BCE. This could have been the first battery ever. What we know for certain is the origins of the modern battery began with Benjamin Franklin in 1749. He was the first to use this term to describe a means of generating an electric charge through the use of chemical elements. Though his method of electrochemical reaction is now known as capacitors which store and release small amounts of electric energy.
The first actual battery, resembling the modern equivalents, came about in 1791. Italian scientist, Alessandro Volta discovered an electric charge resulting from the contact between different metals. In essence he had discovered the first usable power source, the copper zinc battery. This primitive version was not too different from modern non-rechargeable batteries. Those cheap batteries that you often see at the checkout isle.
Long before the electric generator, or alternator was invented, batteries were the only from of electric energy. The concept for a rechargeable battery only came about in 1859 when Gaston Planté invented the lead acid battery.
The original lead acid battery consisted of a lead anode and a lead dioxide cathode in a bath of sulfuric acid. A reaction between these metals and the acid electrolyte formed lead sulphate. More importantly, there was an electron reaction. The resultant effect being a lead anode releasing electrons and a lead dioxide cathode attracting them. This caused an electric current. The anode and cathode being positive and negative poles of a battery. The reaction can be reversed by applying a DC electric current, thereby charging the battery. This cycle of charging and discharging could continue for a long as the lead and lead dioxide electrodes remain viable. The creation of lead sulphate and corrosion cause the lead electrodes to decay over time. The heat generated from internal resistance causes a more rapid deterioration of the battery cell. This is one of the main aspects that has been improved over time.
Modern lead acid batteries use the same original principle. Though later experimentation with alloys and different acid electrolytes have resulted in batteries that last longer and have a greater charge capacity. There have also been advancements in battery cooling, like the use of absorbed glass mat and gel coolant technology.
Other types of rechargeable power storage have replaced the lead acid battery for some applications. Nickle Cadmium batteries were common in many handheld devices that used rechargeable batteries. In most cases, these have since been replaced with lithium ion batteries. Lithium combined with a variety of ionic elements are rapidly becoming the most popular form of battery storage for all applications from small devices to electrically powered cars, as well as mass power storage for solar and wind electric generators.
Understanding the Types of Deep Cycle Batteries
In order to buy the best deep cycle batteries to be used for an RV or home battery, you need to have a clear idea of how the various types of batteries function. The electrodes and electrolytes will define the battery characteristics and, often, the battery price.
Valve-Regulated Deep Cycle Batteries
Valve-regulated lead acid (VRLA) batteries are often called sealed batteries. However this is somewhat misleading as no lead acid battery can be completely sealed. Gas expansion inside the battery needs to be vented. These batteries are more accurately described as recombinant batteries. This means that the oxygen and hydrogen that is released during the charge cycle recombines to form water. The battery remains sealed from the atmosphere during normal operation. When the battery receives a high current charge, the valve will open to safely allow for gas expansion. The vent has built-in gas diffusers to prevent toxic gas from becoming a safety hazard.
VRLA batteries are known as dry cell batteries as the cells are not cooled by a liquid bath. There are two common types of VRLA batteries: Absorbed Glass Mat (AGM) and Gel.
By using a fiberglass mat between the battery cells, the coolant can be regulated. Battery coolant is absorbed by the mat and released at high charge or discharge when the battery generates more heat. This reduces coolant loss through evaporation and reduces the internal resistance of the battery.
Instead of using a liquid coolant, a gel is used. Like AGM batteries, the use of a gel means reduced coolant loss and improved performance through lower internal resistance.
While VRLA gel or AGM batteries are generally more expensive than flooded batteries, they have several advantages.
Lithium-ion batteries have not been around as long as lead acid or Nickel Cadmium batteries. The concept of using lithium as a means of rechargeable power storage was first conceived in the 1970s. The first working prototype lithium battery was developed in 1985. In 1991, Sony and Asahi Kasei jointly released the first commercial lithium ion battery. These early batteries were small, with a low voltage and current output. They were used for low-amperage handheld devices, paving the way for the cell phone revolution that followed.
As the use of lithium ion batteries grew, several safety concerns came to light. One of the primary issues with early lithium batteries was a propensity to self-combust. High temperatures as discharge rates increased, made these batteries wholly unsuitable for high-power applications.
The advent of the electric car as a commercially viable enterprise brought about the need for a more stable lithium battery, capable of higher discharge rates, at a much higher voltage. Today, there are several types of lithium-ion batteries available. There are 6 basic categories of lithium battery, each with their own advantages and applications.
Choosing the Best Deep Cycle Battery
Deciding which is going to be your best power storage option will depend on how you intend using the battery and, of course, your budget. Whether you intend using battery storage for your RV, home backup, or an off-grid home, there are several criteria that need to be considered:
Battery Storage Capacity
You should start by calculating your battery storage capacity requirements. This involves the amount of power you will be using at any given time and the amount of time the battery needs to supply this power before it can be recharged.
Peak and average power demand is calculated by adding the power rating for your electric equipment in kilowatts. If you’re using an inverter to supply AC power, you’ll need to account for conversion loss. Inverters can vary, some may be highly efficient (90% or more), while others can be as low as 70% - 80%. Check your inverter specs and adjust your power requirement accordingly. If an inverter has a 90% efficiency rating, you’ll need to add 10% to your actual power demand in kilowatts.
By listing all your equipment and adding their wattage rating, you get a rough idea of your peak demand. You will need to estimate approximately how many hours each appliance will be used during a discharge period. Your discharge period is the time that you will be relying on battery power before you’re able to recharge the battery.
To obtain your kilowatt hour (KWH) requirement, you’ll multiply the kilowatt requirement for each appliance, multiplied by the estimated running time for that appliance over the discharge period. Then divide the KWH rate by the battery voltage to obtain your AH requirement. In most cases, this will be 12V. You can then assess how many batteries you will need according to the AH rating of the battery you have chosen. If you’re considering a 100AH battery and your AH requirement is 500AH, you will need to connect 5 X 100AH batteries in parallel. If you need a higher battery voltage, you will connect batteries in series to obtain the correct voltage. A 24V battery bank will require two batteries connected in series.
Many people underestimate the importance of the battery charging method and charging intervals when selecting the best battery for a particular application. Lead acid batteries and lithium ion batteries have completely different charging requirements. Using the incorrect battery charger will damage the battery. Another consideration is the consistency of your battery charging method. Solar charging, for example, is not predictable.
Charging Lead Acid Batteries
In the discussion on lead acid batteries, we established that not all lead acid batteries are equal. Cheap, flooded lead acid batteries should not be cycled too deep and need to be recharged to full immediately following a discharge. VRLA batteries are more forgiving with regard to charging cycles. Though, even VRLA batteries will benefit from cycles less than 50% and regular charging.
If you’re using battery power for a short period and are able to recharge the battery soon after discharge, you could use a more economical flooded lead acid battery. This would typically be an RV with a generator. You will use the battery at night for a few hours and then recharge the battery (or batteries) in the morning when you start the generator. If you calculate your battery requirements accurately, ensuring that the battery never discharges beyond 50%, and you know you will always be recharging the battery timeously, cheaper batteries could be feasible.
For home backup power during an outage, you need to consider the average time of an outage. In some areas, power outages can last for a few hours, or several days. For long power outages, VRLA batteries are better as they are capable of deeper cycles. If you only need backup power for a few minutes up to around 4-hours, you may be able to save money, using flooded lead acid deep cycle batteries.
If you’re using a solar charger or require backup power for long periods, you should consider VRLA (gel or AGM) batteries. Because you can never predict the amount of sunlight available, flooded lead acid batteries are no good for solar (or wind) chargers. In my experience, there can several days with little to no sunshine. In some instances, sunlight for charging batteries can be insufficient for weeks at a time. You may have a few hours of intermittent sunlight per day, and this situations can last for several weeks. This means that the battery may receive some charge for a few hours at a time. Though the battery never reaches full charge and, therefore, does not go through a complete cycle This means that the battery cycle is erratic. Instead of battery cycles lasting a few hours, the actual complete cycle (from discharge to 100% charge) can last for weeks. In a situation like this, flooded lead acid battery, that should last for several years, can end up lasting for about a year or less. When you don’t have a predictable rate of charge, you need to use high-quality VRLA batteries. The correct lithium ion battery is usually the best for solar or wind chargers.
When using an AC battery charger, power converter, or solar charger, this needs to supply the appropriate charge for the type of battery you’re using. This is common problem, especially when changing from lead acid to lithium batteries. Ensure that you use the correct charger for the type of battery you’re using.
All lead acid batteries (flooded or VRLA) require a 3-stage charger. This means a high-volt, high-amp bulk charge, followed by a reduced voltage as the battery approaches full charge. As battery charge increases the current (amps) will decrease. Once the battery is fully charged, a float charge is required to compensate for the self-discharge tendency of lead acid batteries.
Charging Lithium-ion Batteries
If you’re using lithium-ion batteries, you will usually require a battery charger designed for these batteries. Most importantly, a lithium-ion battery requires a constant current charger. This will provide a steady amperage which only peaks briefly as the battery reaches full charge. Furthermore, the battery charger needs to shut down once the battery reaches full capacity. A float, or trickle charge, used to maintain a lead acid battery, will damage a lithium ion battery. Some lithium batteries have a built-in battery management system (BMS). These batteries can be charged using a conventional charger, or power converter, designed for lead acid batteries. Because the battery has an internal electronic system to prevent overcurrent and overcharging, it will not sustain any damage when the charger is designed for bulk and float charging.
This is another area of battery usage that is often ignored. Battery lifespan is drastically reduced at high temperatures. Extremely low temperatures actually increase battery life but have an adverse effect on performance. As the ambient temperature decreases, so does the voltage output.
Battery specifications are calculated at 25°C (77°F), this is considered the ideal operating temperature. When a battery is used, or stored at a higher temperature, specified life expectancy and output specifications are reduced. However, some batteries perform better, and will last longer, when used at temperatures higher than the specified 77°. While these batteries should ideally be used below 77°, they are more suitable for higher temperatures.
VRLA batteries are better suited to higher ambient temperatures, as are some lithium-ion batteries, like Lithium Manganese Oxide, Lithium Iron Phosphate, and Lithium Nickel Manganese Cobalt Oxide.
Most modern deep cycle batteries are marketed as being maintenance free. This means that there is no physical maintenance required. With the exception of some lead acid batteries, that may require top-up water, battery maintenance refers mostly to charging and storage requirements.
We’ve already covered battery charging and this is a vital consideration for the type of battery you’re using. I’ll list the important points for clarity.
Apart from these factors, there are a few long term battery maintenance requirements.
Not many people know that a lead acid battery requires a specific maintenance cycle. Some of the high-end 12V battery chargers have a maintenance setting. Though you can do this manually. A lead acid battery maintenance cycle needs to be conducted about once a year. This ensures that the electrolytes remain active and prolongs battery life. An annual battery maintenance cycle involves rapidly discharging the battery to 100% of its discharge capacity. You can do this by placing a high load on the battery until it has no more power. This discharge should be followed, immediately, by a complete charge cycle without any interruptions.
Storing a battery correctly is also important. When unused, batteries need to be charged periodically as follows:
By charging batteries at these minimum intervals, you compensate for battery damage that results form self-discharge.
Deep Cycle Battery Frequently Asked Questions
What is the best battery for RV use?
An RV can have one or two battery systems. A motorhome will have a vehicle battery, for starting the engine. It may also use leisure batteries to supply power for onboard equipment like lighting, pumps, refrigerator, and electronic devices. If a motorhome vehicle battery is used only for cranking the starter, a conventional automotive battery is sufficient. If this battery is used for engine cranking and auxiliary items, like electric awnings, a cranking deep cycle battery is best. For supplying electric equipment inside an RV (lighting and appliances), deep cycle leisure batteries are required.
How long does a deep cycle RV battery last?
It is never easy to predict battery life. Depending on the type of battery, and how it is used, a deep cycle RV battery can last anything from 1-year up to 15-years, possibly more. If a battery is charged, discharged, and maintained correctly, you should expect a flooded lead acid battery to last 3 – 5 years. A quality VRLA lead acid battery should last 7 -10 years, and a quality lithium-ion deep cycle battery should last 10 – 15 years.
All batteries are rated for a certain number of cycles (usually up to 80%). If a battery is rated for a 1000 cycles, this means that the battery can be discharged to 80% of total capacity and then recharged 1000 times. Most lead acid deep cycle batteries last longer when used at less than 50% of capacity before recharging.
Is there a difference between deep cycle and marine battery?
Marine, or leisure battery, is another term for a deep cycle battery. They all mean the same thing.
How do you bring a deep cycle battery back to life?
Typically, when a battery has reached the end of its rated life, it should be safely disposed of. However, you can try revive a lead acid battery by adding distilled water and sulfuric acid, then charge it to full capacity. There are some “cowboy” methods, but I would not recommend these, as they are dangerous and seldom produce any real results. These include reversing charge polarity and using a higher voltage for charging. I cannot recommend these methods for safety concerns and will, therefore, not offer any advice on how to do this. Never try revive a lithium-ion battery once it no longer produces a usable voltage.
Can you overcharge a deep cycle battery?
If a lead acid deep cycle battery continues to receive a high current beyond bulk charging it will overheat. This can be dangerous and will shorten the life expectancy of the battery. If a lithium-ion battery continues to receive current once it is fully charged, heat damage will also occur. The correct battery charger, or power converter, for the type of battery that you are using will prevent overcharging.
Can I run a staring battery and a deep cycle battery in parallel?
Although a deep cycle and starting battery will work when connected in parallel, it usually will be a costly mistake. These batteries will generally discharge at different rates. This means that the deep cycle battery will end up supplying current to the starting battery, resulting in increased battery cycles which will reduce battery life.
What is the best way to charge a deep cycle marine battery?
Using a quality battery charger or power converter is the best method of charging deep cycle batteries. It is important to use the correct charge current. Smaller lead acid batteries usually charge at a lower amperage (10A or less). If you are uncertain about the best charge current, select the lowest amp setting on your charger. A lead acid battery will accept any current. Using a low amperage setting will increase charging time but will prevent heat damage. A lithium ion battery has to use a constant current charger rated for that battery.
When Should you use a deep cycle battery?
A deep cycle battery should be used for any application that requires long discharge cycles. Regular 12V automotive batteries are designed for a discharge of a few seconds. Whereas deep cycle batteries are designed to provide power for several hours, even days in some cases.
How do I know if my deep cycle battery is bad?
A deep cycle battery is considered unusable when the voltage upon discharge drops rapidly. Visible signs of a bad battery will include bulging or fluid leaks. If a battery takes a long time to reach full charge and generates excessive heat, it is nearing the end of its life.
The best way to check your 12V battery is by conducting a voltage and load test. Charge the battery until the charger indicates full charge. Disconnect the battery from the charger. Using a multimeter, check the battery voltage with no load (open circuit). The ideal open circuit voltage for 12V battery is around 13V. When you place a load on the battery (closed circuit), the voltage should remain at 12V or more. If the voltage drops below 11V under load, it is time to replace the battery.