Howdy! Today I am going to talk about one of the most critical components of your rig, the batteries. When it comes to RV batteries there are multiple types, sizes, applications, and ratings. If you are looking to upgrade or need to replace your battery(s) it can be a little overwhelming if you are not an expert. In this blog, I’m going to inform you about RV batteries in detail. You will get information on how they work, what makes some batteries better than others, and the different options that are available. Let’s dive right in!
First, I would like to provide a brief explanation of what a battery is and how it works. Batteries store electrical potential energy in a portable container. Most batteries in RVs from the factory are lead acid and have multiple cells that are connected in a series to produce 12 volts. Each cell is composed of an anode (a positively charged electrode), cathode (a negatively charged electrode), and electrolyte solution that undergoes a chemical reaction to create electricity when in use, or to store electricity when charging the batteries. The cells in a RV battery produce about 2.1 volts and when 6 cells are in series, they produce about 12.6 volts when fully charged. Hence the name for your RV’s electrical system being called the “12-volt system”. Now that we have a better understanding of what a battery is and how it works, let’s talk about the two types of RV batteries in detail.
Chassis batteries are also referred to as “starter batteries”, and rightly so as their only function is to start the engine. These batteries produce a large electrical current but only for a brief period of time. The internal composition of this type of battery is actually different from house batteries so that these batteries can produce a lot of power quickly, and on command.
The rating system for chassis batteries is in CCA’s (Cold-Cranking-Amps). CCA is the number of amps the battery can deliver at 0 degrees Fahrenheit for 30 seconds and not drop below 7.2 volts. The CCA rating depends on the size of your engine. The bigger the engine, the more CCAs you will need to start it. There are also different “groups” or sizes and terminal locations of the battery. Most chassis batteries will display the CCAs and group size directly on the battery in case you need to replace. If you are unsure of the CCAs or group size, this info will be in your owner’s manual. Because chassis batteries are designed to deliver a lot of electricity, but only for a short period of time, they are not well suited for house battery applications.
House batteries power the cabin of your rig. Both the chassis and the house run on a 12-volt system. However, as mentioned in the paragraph above, chassis batteries are not well suited for house applications because they do not provide consistent power for extended periods of time. House batteries are designed for “deep cycle”, or extended use applications. Deep cycle batteries are designed to be charged, and discharged numerous times while providing a consistent amount of current. These batteries are rated in Amp Hours (AH) or Reserve Capacity (RC).
The amp hour rating system is more common and consists of two components, time and amperes (amps). Amp hours are defined, as the name suggests, by how many amps the battery can deliver for how many hours before the battery is discharged. For example, a battery that could deliver 10 amps for 10 hours before being discharged would have an amp hour rating of 100AH. In simple math terms, 10amps x 10hours yields 100AH. This same battery could produce 5 amps for 20 hours.
Reserve capacity takes three components into consideration: amps, time, and a temperature of 80 degrees Fahrenheit as a constant. RC is calculated by how many minutes the battery can deliver 25 amps until it reaches a discharge condition (delivering less than 10.5 volts). The good news is that RC can easily be multiplied to the more common AH. If you would like to convert RC into AH, multiply RC by 60 percent (0.6).
Now that you understand the rating system for the house batteries, let’s talk about the different types of RV batteries. There are five primary types of batteries used for RV house application and each battery differs based on the materials the battery is made of and the electrolyte solution used inside the battery.
The first two types of batteries are both “flooded” (containing liquid electrolyte solution) lead acid batteries and can be either serviceable or maintenance free. As the name “lead acid” would suggest, the battery is composed of lead plates and sulfuric acid that undergo a chemical reaction to produce electrical current.
The next step up is a Valve Regulated Lead Acid (VRLA) battery. These batteries contain a different type of electrolyte solution like gel, or saturated fiberglass. Batteries that contain gel for their electrolyte solution are called “Gel Cell” batteries. Batteries that contain fiberglass saturated electrolyte mats between plates are called Applied Glass Mat, or “AGM” Batteries.
Newer to the RV market is lithium-ion batteries. These batteries have a lot of advantages over lead-acid batteries that you will read about below. Most commonly, the electrolyte for Lithium-ion batteries is composed of lithium salt. The biggest advantage of the lithium-ion battery is the electrolyte solution is much more efficient for storing and generating electricity.
Let’s take a look at the pros and cons of the 5 most commonly used deep cycle RV batteries –
Serviceable Lead Acid Batteries
-Least expensive battery option for replacement
-Easy to find; multiple brands and styles to choose from
-No special charging requirements
-Require maintenance (topping off electrolyte solution) and inspection every 3-6 months if battery is serviceable
-Maintenance can be difficult depending on the location of batteries
-Extreme climate conditions can have a greater impact on the battery life, since the electrolyte solution inside the battery is at risk of evaporate in hot temperatures or freezing in cold climates
-Shorter lifespan than Gel, AGM, Lithium-ion counterparts
Maintenance Free Lead Acid Batteries:
-Battery electrolyte solution is sealed and does not need to be serviced
-Budget friendly option for replacement
-Like serviceable batteries, these batteries are easy to source and there are lots of options.
-More expensive than serviceable batteries
-Not guaranteed to be leak free like AGM, gel, or lithium batteries
-Shorter lifespan than gel, AGM, and lithium-ion counterparts
Gel Cell Batteries:
-Completely leak free
-Withstand high temperatures very well
– Gel batteries require slower charging cycles at voltages lower than those used for flooded cell and AGM batteries
– Gel cell batteries can be permanently damaged if overcharged
– Require a charge controller compatible with Gel batteries
Applied Glass Mat (AGM) Batteries:
-Not vulnerable to freezing
-No special charging requirements
-Lifespan is generally 2-3 times longer than flooded lead-acid batteries
-Not affected by vibration
-Usually around twice the cost, if not more expensive than a flooded lead acid battery
-Typically, 30% lighter weight than lead-acid alternatives
-Provide the most amp hours and can create the most efficient battery bank
-Longest life cycle and highest capacity compared to other batteries.
-Overall, highest performance battery available on market for RV use
-Substantially more expensive that lead acid, gel, and AGM batteries
-Due to limited manufacturers, there are not many options available on the market
Each type of battery has its advantages and disadvantages. When clients would ask me which type of batteries I recommend, I would always ask how they primarily use their RV. If a client usually kept their rig plugged in, did the occasional dry camping, and could afford the AGM batteries, I would recommend the AGM batteries as a great overall value. If a client told me that they would be doing a lot of dry camping, or wanted to be “off-the-grid” I would recommend lithium-ion batteries because you can build the best power bank and have the most amp hours for use between charges. For most clients who were concerned about budget, serviceable, or maintenance free flooded batteries worked just fine. One thing to keep in mind however is the extreme heat that we face here in AZ, flooded lead acid batteries will have a significantly shorter life span than their gel, AGM, and lithium-ion counterparts.
Use, maintenance, and storage are the other determining factors for how long your deep cycle batteries will last. Deep cycle batteries do not like to be under charged, or overcharged. Incomplete recharging causes sulfates to crystallize on the discharged parts of the plates. The crystalized sulfates reduce the charge capacity of the battery plates and as they build up over time, will damage the battery. This process is called “sulfation” and can happen if the battery is discharged for an extended period of time as well. If batteries are overcharged, the plates begin to corrode and the electrolyte mixture loses water.
If you have serviceable batteries, always keep distilled water on hand. Distilled water can be put in the battery through service inlets, usually on the top of the battery and can replenish the electrolyte solution. With all batteries, check the terminals every few months to make sure that there is no corrosion around the terminals. Chances of terminal corrosion is much less with sealed or maintenance free batteries, but is not impossible.
When storing your batteries, clean the batteries with a 50/50 mixture of baking soda and water if there are any signs of corrosion. Store the batteries in a cool dry place but not where they could freeze. Batteries in storage will lose their charge over time. Check the state of charge every month and charge batteries that are at or below 80% state of charge. If you do not want to constantly keep an eye on batteries in storage, look into an RV battery trickle charger to keep the batteries topped off when not in use.
Just like the chassis batteries, the deep cycle house batteries also come in different sizes designated by the group number. Some common group sizes include 24, 27, and 31. It does not come as a surprise that the larger the battery the more amp hours you can get out of a battery.
Depending on how much space you have in your RV, and how your batteries are wired, you can customize the house battery bank. There are two wiring configurations for connecting the batteries in your RV together. To customize the battery bank in your RV, batteries can be connected in parallel, series, or in some cases, both.
For example, a single group 27 12v battery is rated at 85-105 amp hours. Wiring two of these group 27 batteries in parallel will keep the same voltage, but double your amp hours to 170-210. An example of running batteries in series would be to use two, 6v golf cart batteries and wire them together to make 12v. This is a popular modification amongst RV owners. Golf cart batteries, like RV batteries come in the same flooded, gel, AGM, and lithium ion varieties.
Lets use flooded batteries for an example. Two of the 6v golf cart batteries in series can produce around 180-220 amp hours. Running batteries in both parallel and series, would be to wire 4 golf cart batteries together to produce 12v and roughly 360-440 amp hours. Running in series, parallel, or both can be a great format to double or triple the battery bank in your RV.
If you have made it to the bottom of this article, well done! You are now an expert on how RV batteries work, the different types of batteries, applications, and the pros and cons each type. You will also be a pro on maintenance, proper charging, and how to upgrade or modify your battery bank when the time comes. Always remember that there are options when changing or modifying your batteries and make sure that you are doing what is best for your RV lifestyle. If you have any questions, or would like a recommendation, please feel free to reach out to me at Kevin@UCRVAZ.com.