Starting, Deep Cycle & Dual Purpose: Breaking Down Your RV Battery Options

Power - by Joe Weber - updated on 5/23/2024

When shopping for RV batteries, it's important to understand that specific batteries are designed to power different applications. Starting batteries do not function in the same way as deep-cycle batteries, and if you use them interchangeably, you could drastically shorten the life of the battery. This article will help you understand the different types of RV batteries and how they should be used.

What are the Three Types of RV Batteries?

Deep Cycle Batteries - A deep cycle battery functions as the "house" battery on an RV. These batteries are used to power appliances and other electrical systems when the RV is not connected to shore power. Unlike starting batteries that provide short, intense bursts of power, deep-cycle batteries provide ongoing power for longer periods. Learn all about deep-cycle batteries in our recent article "What is a deep-cycle battery?".

Starting Batteries (also known as cranking batteries) - Just like the batteries in your car or truck, RV starting batteries are built to deliver the short, intense burst of power necessary to start your RV's engine. They are not designed to provide long-term power and should not be used in place of a deep-cycle battery.

Dual Purpose Batteries - Dual purpose batteries offer the best of both worlds, a starting and deep cycle battery in one. They can provide the initial burst of power necessary to start your engine and provide the long-lasting cycling power required to operate your onboard electronics and appliances.

How Are Flooded, AGM and Lithium RV Batteries Different?

In addition to the three different battery types, there are also three different battery chemistries available: flooded (wet cell) lead acid, AGM (short for Absorbed Glass Mat) and Lithium Iron Phosphate (LiFePO4).

The chemistry of the battery you choose will have a major influence on how long it will last, how fast it will recharge and other aspects of performance. Here is a breakdown of the different chemistries.

Flooded Lead Acid Batteries

• Available in all three types, starting, deep cycle and dual-purpose.
• The most affordable option between the 3 battery chemistries.
• They do feature the shortest lifespan of the 3 battery chemistries.
• Flooded batteries are not completely sealed and do require regular checks of the electrolyte levels inside the battery and distilled water should be added any time the plates are exposed.
• Flooded batteries feature a high rate of self-discharge in storage.

AGM Batteries

• Available as a starting, deep cycle or dual-purpose battery.
• AGM batteries have a higher initial investment than flooded batteries.
• Can last 2-3 times longer than flooded batteries.
• Are completely sealed and require no electrolyte maintenance.
• Have a slower self-discharge than flooded batteries in storage.
• They can charge up to 5 times faster than flooded batteries.
• AGM batteries are more resistant to extreme temperatures and vibrations.

Lithium Iron Phosphate Batteries

• LiFePO4 is available as a deep-cycle battery only.
• They have a higher initial investment over flooded and AGM batteries.
• Lithium batteries last 4-5 times longer than a flooded battery.
• Completely sealed and can be installed in multiple configurations to fit your RV.
• Feature the lowest self-discharge of the 3 battery chemistries; rarely needs to be charged while in storage.
• Can be deeply discharged further than the other battery types before it must be recharged.
• Charges 4 times faster than most AGM batteries.
• Are more resistant to extreme temperatures and vibrations.
• Lithium batteries weigh 50% less than lead-acid batteries.

How Many Batteries Do I Need In My RV?

Depending on the amount of electronics and appliances in your RV, you may require several batteries to power it all. Smaller RVs with few battery-reliant appliances onboard may be able to rely on a single starting or dual-purpose battery. Most RVs, however, will require a starting battery and at least one deep cycle battery, or a dual-purpose battery either by itself or paired with several deep cycle batteries.

Important Note

Don't mix battery types. You can use a dual-purpose battery for a starting battery and deep-cycle batteries for the home power but don't have a mix of dual-purpose and deep-cycle both powering your appliances. This is not a good practice for battery health.

Something else to take into account when determining how many batteries you need is how many Amp-hours (Ah) you need to run all of the appliances in your RV. Calculating the total power (in amp hours) that your appliances require per day will help you determine the size and number of batteries you need. Here is how to do that:

• Start by making a list of all of the appliances in your RV.
• Determine how many amps each application requires to run. (This information is usually listed on the label of the item or it can be found online.)
• Multiply the number of amps each application requires by the number of hours you plan on using that appliance per day. This will give you the total power consumption of that appliance for the day.
  • For example, a laptop uses 5 amps of power. If you plan on using it 3 hours a day, your total daily power consumption for the laptop would be 15 amp-hours of power.
• When the list is complete, add up the daily power consumption of each appliance to tabulate your total power consumption (in amp hours) per day.
• Once you have added up your total power consumption for the day, select a battery (or batteries) with a high enough amp-hour rating to cover your electrical demands.
  • It's recommended by most battery manufacturers that your batteries are not discharged more than 50% of their total capacity, especially for lead-acid batteries, for the best lifespans. In this case, you'll need to divide the battery's listed number of amp hours by two. This will give you the actual usable capacity for the battery. For example, a 100Ah battery will only provide you with 50Ah of usable capacity before it needs to be recharged.
  • Lithium iron Phosphate batteries can discharge much lower than lead acid batteries so you don't need to cut their amp hour total. See the manufacturer's recommendations to determine how low they can be discharged.

How Do I Charge RV Batteries?

Once you have your batteries picked out, it's time to talk chargers. While your alternator will charge your RV's starting battery as you drive, you will need separate chargers for your deep-cycle batteries to keep them topped off and healthy. Our selection of marine battery chargers can also be used for RV deep-cycle batteries.

Batteries Plus is Your RV Battery Headquarters

Still have questions? No problem! Stop into your nearest Batteries Plus and ask your questions face-to-face, or visit our blog has plenty of additional information to help you make an informed buying decision. Some related topics include "What Does 100Ah Mean on a Battery?", "How to Maintain Your Boat or RV Battery Over the Winter" and much more.