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battery care, Electrical System, RV Batteries, RV battery types, RV Electrical System, RV Electrical Tips, RV Safety, RV tech tip
“What is the best battery for my rig?” The best or correct battery for your rig depends on a variety of factors such as:
- How often will you be boondocking/dry camping?
- How many 12-volt components will you be running and for how long?
- How long do you plan on staying out before needing to recharge your batteries?
- What type of budget do you have?
Most battery manufacturers make a variety of batteries for different applications. To start with, let’s look at the different types of batteries starting with cold cranking amp and deep cycle types.
Start/Engine Batteries
Cold Cranking Amps (CCA) is a term used to identify the batteries’ ability to start an engine in cold weather. Since it’s harder to start an engine in cold weather, the higher CCA means more amp power available to turn the engine over and start in a 30-second time frame. This type of battery should not be used in your house battery application.
Deep Cycle/House Batteries
A deep cycle battery simply stores energy to provide steady power to 12-volt components in your RV such as lights, water pump, roof vents, and any appliance that runs on LP such as the stovetop, water heater, furnace, and others. It is designed to be discharged and recharged repeatedly which is known as a cycle. This type of battery is the best for an RV application.
Most RVers are concerned about the “best” house battery for their rig rather than the start battery so let’s look at the different types of deep-cycle or house batteries available.
Flooded Lead Acid (FLA)
The flooded lead-acid battery has been around for years, in fact, it was invented in 1859 by a French physicist well before any RV hit the road and there have been quite a few improvements over the years.
Lead plates are surrounded or submerged by an electrolyte solution of sulfuric acid and water and require more maintenance as water is lost during recharging and distilled water should be added periodically. They are also more prone to sulfation if not recharged properly with a multi-stage charger. They also need to be stored upright otherwise electrolytes will spill out the vent caps. These batteries tend to be the most cost-effective.
Absorbed Glass Mat (AGM)
AGM batteries also have lead plates with an electrolyte solution, however glass sheets or “mats” are used to absorb the solution and due to the design, there is no gassing or solution loss and less maintenance. They are also sealed and can be stored in an out of the way location without the need to check fluid levels or worry about leaking. These batteries are typically twice the price of FLA batteries.
6-Volt vs 12-volt
Whether you have FLA or AGM batteries, there are two different schools of thought in what RV manufacturers decide to use: 6-volt batteries connected in series, or 12-volt connected parallel. In either case, the end result is a 12-volt DC system! 6-volt batteries require two batteries that are connected positive to negative which is called in-series and creates a 12-volt battery bank.
Connecting two 6-volt batteries in series does not double the amp hours, to do that you need to add two more 6-volt batteries in series and connect them parallel to the system. The advantage of the 6-volt battery is they typically can by “cycled” or discharge and recharged more often so they will last longer but do not provide more power or amp-hours.
A single 12-volt battery can be used as a cost-effective method to provide power. Additional amp hours can be added with one more 12-volt battery connect parallel which is positive to positive. This will double your available amp-hours.
Battery Size-Amp Hours
Deep cycle batteries are rated in groups, or available amp hours which is how long a battery can provide power before being discharged. Here are some of the common amp-hours per group:
Group 24 – 70-80 amp hours
Group 27 – 80-100 amp hours
Group 31 – 100-130 amp hours
This means that the 100 amp hour battery will provide 1 amp of power for 100 hours. However, we will use much more than 1 amp per hour so we need to determine what is being used and keep in mind that most batteries can only be discharged 50% before shortening the lifespan of the battery.
To calculate the best battery for your needs, start by determining how much time you will be boondocking or dry camping. Then identify what components you will be running and for how long. Any appliance that uses LP such as the refrigerator, stovetop, oven, and water heater will use 12-volt power, however, they will not be running full time. Items like interior lights, roof vent fans, and water pump will also need to be factored in.
If you are going to be camping with access to an electrical source, you can get by with a small group or amp hour battery and save some money as your converter will recharge your batteries.
Here are some typical 12-volt components and the amp draw from them
- Incandescent Lights = 1.5 amps
- Halogen Lights = 1 amp
- LED Lights = .12 amp
- Smoke Alarm = 1 amp
- CO Detector = 1 amp
- LP Leak Detector = 1 amp
- Furnace = 10-12 amps
- Water Pump = 5 amps
- Refrigerator on LP Mode = 2-3 amps
- Stove Top = 1 amp
- Roof Vent = 3 amps
As you can see, there are several factors in what usage you might have in your rig, especially if you are camping in cold weather. It’s not uncommon for a smaller rig to have a 10-15 amp draw which means you will only get about 4 hours with a group 24 battery! Here is the math:
80 amp hour battery x 50% = 40 amp hours
40 amp-hours / 10 amps drawn every hour = 4 hours of battery life
The more you use and the longer you need to stay out before recharging with either a generator or solar panels, the more amp hours you will need.
One other important item to consider when looking for the best battery for your application is the quality of the battery. Several discount franchises offer a cheap “Marine/RV” deep cycle battery and the only feature of those batteries is the cheap price. They are made with thinner plates, insufficient lead oxide paste and acid ratios, and inferior welds on intercell connections. In short, they sulfate faster and go bad with dead cells and less storage quicker. I would recommend getting a battery endorsed by the RV industry such as Trojan, Lifeline, and even NAPA batteries are being used with much success. Take some time researching the information on the website about thicker positive plates used and superior workmanship and you’ll find you get what you pay for.
In summary, the best battery for your application is not a simple answer, rather a calculation in the way you are planning to RV.
About the author: Dave Solberg: Managing Editor, RV Repair Club
For the last 25 years, Dave has conducted RV maintenance and safety seminars, developed dealer and owner training programs, written RV safety and handyman articles, authored an RV handbook reference guide and logged over 100,000 miles on the road in an RV.
RV Repair Club is your go-to online resource for enthusiasts who want quality RV maintenance, repair and upgrade information – a community where passionate RVers can come together to gather knowledge and share their experiences.
Learn more about RV Repair Club.
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12-volt Deep Cycle batteries are the lifeline for RV enjoyment. Not only do they power the common 12-volt functions like lights, roof vents, and such, but are also essential for powering any appliance running on the LP mode and even the absorption refrigerator on the 120-volt mode as the temperature sensor and monitor panel are powered by the 12-volt batteries!
Then came the AGM or absorbed glass mat battery which was maintenance free and literally had fiberglass mats inside the battery to absorb the acid and could be stored sideways! Many RVers believe that replacing the lead acid batteries with AGMs will double the power available. This is not true, rather the AGM batteries require less maintenance and are less prone to sulfation. This makes them a more powerful battery only after the lead acid batteries develop sulphur between the plates and lose storage capacity!
