A Word on RV Deep Cycle Batteries: The Different Types
If you’re travelling the country with an RV, it’s important to have all the commodities and conveniences of your home with you on the road, a large part of which are your electrical appliances. Whether it’s a fridge, TV, laptop, electric stove, or anything else, it needs electric power to run, which can be scarce when you’re in a remote area. For that reason, most RVs have solar systems installed on them.
The solar system on your RV, however, will only be as good as the battery that stores the power harnessed from the sun. For most solar RV applications, deep cycle batteries are the best, if not only choice. These batteries provide reliable power under any condition, something that can be really appreciated when you’re in the middle of nowhere.
What’s the difference between conventional and deep cycle batteries? Deep cycle batteries are designed for regular deep discharges, even at quicker rates by power-demanding appliances like microwave ovens, RV fridges, air conditioners, etc. The deep cycle battery range for RV solar systems is almost entirely comprised of lithium batteries.
They can power your demanding appliances, then recharge at an extremely rapid pace. In other words, these batteries have the ability to accept and release rapid charge rates. They’re almost five times quicker than their AGM counterparts, which are the next most advanced type. But that doesn’t mean everyone needs lithium deep cycle batteries for their RV. If you don’t have a lot of demanding appliances in your RV, you probably don’t need them. Other options may work just as well for you.
Flooded lead-acid batteries, for example, which are constructed of lead grids or plates in a container. They’re called flooded due to the fact that the plates are submerged in a liquid electrolyte. When charged, the positive plates add lead dioxide, whereas the negative ones are lead-antimony, and the electrolyte is concentrated sulfuric acid. As the flooded lead-acid battery discharges, the plates become lead sulfate, and the electrolyte loses most of its sulfuric acid, changing to water.
These batteries have been around for quite some time now and they offer a few distinct advantages. They’re the most affordable, for instance, are widely available, and they’re suitable for a wide range of uses. However, they aren’t ideal for use in RVs, as you’d have to install them in a special battery box, as you’ll need to water it regularly. At the same time, the box needs to be vented outside and sealed off from your RV’s interior as it generates some poisonous gases.
Sealed lead-acid (GEL) batteries are another type of deep cycle batteries that resolve some of the issues flooded lead-acid batteries face. As their name may suggest – their electrolyte is gelled, so it isn’t prone to spills, can be used in areas without ventilation, and they can be mounted both horizontally and vertically. GEL batteries don’t have as much energy density as AGM batteries, and they demand significantly slower charging, which are two of the main drawbacks.
AGM is another type of sealed lead-acid battery. AGM stands for absorbed glass mat, and these batteries are the most popular ones for RV use by far. Unlike flooded models, all the liquid electrolyte in these batteries is absorbed into fibreglass mats, making them spill-free. But their best feature is their ability to be charged significantly faster than all other types of batteries, and their ability to deep-cycle. AGM batteries have a very low self-discharge rate and thus don’t suffer from sulfation as much. Most models don’t tolerate or need an equalizing charge, and they can be safely locked inside your RV, although it’s recommended to place them in a battery box.
I briefly mentioned lithium batteries in the starting paragraphs, but I didn’t touch on how they work. These batteries are much different from the other deep cycle batteries I talked about. They still feature an anode and cathode, but instead have lithium ions move between them, usually in a solution of lithium salts. The cells in these batteries can be either small or large cylinders, plastic rectangular prismatic or soft plastic pouch cells. In other words, they’re available in many chemistries, and the most stable, safest and long-lived variation are lithium iron phosphate batteries.
Compared to other battery types, these batteries have a lower energy density. However, they have a rather flat discharge curve, are less prone to thermal runaway, and have the longest life expectancy out of all lithium batteries, as long as you maintain them well with moderate temperature conditions and good charging practices. These batteries don’t release any gas whatsoever, and they can be completely discharged without any damage.
Lastly, they’re more lightweight than other batteries, and they can accept very high charge rates. For instance, you can charge a 100Ah battery with 100A. However, you should expect to pay slightly more for a good lithium deep cycle battery.