THE VOLTS ARE IN
Understanding how motorhome batteries operate, and how to maintain them, can lead to EASIER travels
When all goes well on an RV trip, we rarely stop to reflect on the systems and components we rely upon to have a positive experience even when our surroundings may be less than accommodating. And when it comes right down to it, batteries may be the single most important part of the equation; they get the motorhome started, run the 12-volt DC electrical system, even operate some 120-volt AC appliances with the help of an inverter. As such, understanding how they operate, and how to maintain them should be considered a priority — or they’ll get your attention by failing at the worst possible time.
A Little History
Batteries have been starting motor vehicles since about 1912 when Cadillac put an electric starter on production models. Less than a decade later, Ford ditched hand-crank starting on its Model T, and the rush for batteries was on.
Way back then, a battery was made of lead and acid, and you might be surprised to learn that the majority of batteries today are still made with essentially the same ingredients. The rechargeable battery that starts a motorhome engine is typically a lead-acid type that uses six galvanic (electric currents produced by a chemical reaction) cells in series to provide a 12-volt system. The battery usually has six plates of lead, additional lead dioxide plates, and is submerged in a solution of sulfuric acid and water called electrolyte. The resultant chemical reaction releases electrons and allows them to flow through conductors to produce electricity. This type of battery is called a flooded cell.
Now, more than 100 years later, the demands that we put on batteries have gone up dramatically. Just starting the engine is only one of its duties. Today’s motorhomes often come with navigation units, power-adjustable seats with electric heating and more. And over the years, consumers have found plenty more electric-powered devices to add to their rigs too, from auxiliary lighting to power-operated steps, awnings and more.
As the years progressed, battery technology changed to keep up with rising demands. Flooded-cell batteries are still the most widely used batteries today — but perhaps the greatest advancement was the valve-regulated lead-acid (VRLA) design. Commonly called sealed lead-acid batteries or maintenance-free batteries, VRLA batteries are sealed and have a one-way valve to vent gases if they exceed atmospheric pressure by a selected amount.
A gel battery, also known as gel cell, is one in which silicates are added to the electrolyte material to make it a gel. These VRLA batteries are of the maintenance-free variety but should not be confused with absorbed glass mat (AGM) batteries, which are incorrectly referred to as gel-cell batteries. An AGM battery utilizes a fiberglass mat material in which the electrolyte has been absorbed. These batteries are therefore “dry” internally and are more resistant to vibration and shock than their flooded-cell counterparts.
Starting Batteries Versus Deep-Cycle
Every RVer has two types of batteries to deal with: the batteries that start the engine (and typically the generator, if so equipped), and deep-cycle batteries that provide 12-volt DC power when not plugged in.
When considering a new starting battery, most owners are prone to the bigger-is-better mentality, but you might be surprised to learn that this isn’t always the case. For example, most of us gravitate toward the battery with the highest possible cold cranking amps (CCA) or the ability to start an engine in cold temperatures. Those of us who live in hot climates likewise gravitate toward high-CCA batteries because we know that hot engines can also be difficult to crank, but in this case, higher CCA is not the solution. The higher the CCA rating, the more plates per cell the battery has, which displaces the liquid electrolyte and actually makes the battery run hotter. A hot battery doesn’t perform as intended, and won’t last as long.
Since most motorhomes have electrical accessories that can be used when the engine is turned off as well as parasitic components like stereo presets and the carbon monoxide (CO) detector, it’s possible to exceed the capacity of the stock battery and discharge it more than it was intended. This is why you should seek a battery with maximum reserve capacity. This attribute, which often isn’t on the battery’s label, is the amount of minutes the battery will take to discharge with a 25-amp draw. For example, a 120-minute reserve-capacity battery would be completely discharged after two hours but could still possibly start the engine after one hour. The counterperson at an auto parts store should be able to look up the reserve capacity of the battery (or batteries) you’re considering. Alternately, the technical services department of a battery company can also help you find a battery with adequate reserve capacity.
A deep-cycle battery delivers a lower level of power for a much longer period of time. Deep-cycle batteries don’t have as many CCA as starting batteries and won’t provide as many starts. However, where a starting battery might survive only 20 to 30 deep discharges, a deep-cycle battery can withstand repetitive discharges to a 50 percent depth of discharge or more and continue to provide the rated capacity after hundreds of cycles. This characteristic, combined with more reserve capacity, makes deep-cycle batteries ideal for use in an RV application.
A deep-cycle battery differs from a starting battery in its internal construction. There are typically fewer plates inside a deep-cycle battery than a starting battery, but they are normally thicker and hold more lead-oxide paste, which chemically reacts with the sulfuric acid of the electrolyte. The paste itself is usually a higher density as well.
In an RV, reserve capacity is the primary consideration, and you can get more by going bigger, by adding batteries, or by doing both. Most motorhomes have more than one house battery, and if they suit your needs already, you may choose to go with direct replacements, or upgrade to bigger batteries, if they’ll fit. You’ll want batteries with the highest amp-hour (Ah) rating you can find. For example, a 100-Ah battery is one that will produce 5 amps for 20 hours at 80 degrees Fahrenheit (26.7 Celsius) before it reaches 1.75 volts per cell, or 10.5 volts.
For those with more demanding power needs, adding 12-volt batteries and connecting them in parallel will double the amount of time before the batteries are discharged. If you go this route, you might as well opt for 6-volt golf-cart batteries, which are connected in series to produce 12 volts. This setup can endure more deep discharges than a 12-volt marine/RV product (sometimes twice as many), which makes it popular with motorhome owners who want the ability to operate their rigs through an inverter on battery power only. Remember: Parallel combines amps, not voltage. Series combines voltage, not amps.
If your motorhome has multiple batteries, it’s important to consider them as a single system. As such, it’s not a good idea to replace or upgrade only one battery; all of the batteries should be replaced with the same size and type. Placing a new battery in parallel with older or weaker batteries makes the new one work harder and will eventually make it as weak as the others.
Battery maintenance is the key to long-lasting performance, although it’s typically not required as frequently as it once was. Though the vast majority of batteries in use today are the flooded-cell variety, most of these, even those with removable caps, are still considered maintenance-free under normal conditions. However, it is still a good practice to have the battery visually inspected and tested every few months.
If the battery does require water, it is preferred to replenish with distilled water, though tap water is acceptable in a pinch. Also, make sure that the electrolyte (water) covers the plates inside by a minimum of ½ inch. If air contacts those plates for any length of time, it hardens the chemical-paste material on the plates and causes them to sulfate. Once that happens, there is a good chance that part of the plate is not going to be chemically usable anymore. In other words, the percentage of battery performance that’s lost is not coming back.
Keeping batteries charged is obviously important, but what may not be so obvious is how to keep them charged. Leaving a motorhome plugged in when not in use isn’t necessarily a good idea, as an overzealous charger can cook the batteries dry. A simple check is to plug the rig in for about a week; if the battery gets hot or loses water, it’s being overcharged and shouldn’t be left plugged in. Otherwise, the charger can be plugged in for a couple of weeks at a time, but a more reliable solution is to charge the batteries for a day or so once a month. This will keep them topped off without the danger of overcharging.
If the batteries are removed from the motorhome and you want to recharge them, make sure a compatible battery charger is used. It is best to recharge batteries at a current (amp) level of battery amp-hours divided by 5 for fast charging, 10 for slower charging. Example: A 100-Ah battery divided by 5 equals a 20-amp charger. Many battery chargers have adjustable amp settings, which is handy for different battery types.
Battery maintainers are also a popular choice for keeping batteries topped off, but here again, make sure it’s compatible with the battery or batteries. Prior to using the maintainer for an extended period of time, make sure the unit is actually maintaining the proper voltage and check to see if it’s making the battery lose water. After a few days, disconnect the maintainer for a couple of hours and then use a voltmeter or hydrometer to check the level of charge. A voltmeter should be around 12.7 to 12.8 volts, while a hydrometer should show a specific gravity number of 1.265 to 1.275, meaning the battery is at or near 100 percent charged.
After the batteries have sat for several months without charging or being on a maintenance charge, they may require equalization. While this is a fairly involved topic unto itself, suffice it to say that equalization is a term meaning to de-sulfate or equalize individual cells of a battery. This is done through the use of a charger or converter that has the ability to charge at a high voltage (typically 15.6 to 16.2 volts) at a low current level in an attempt to break the sulfate crystals off the inner-cell paste material. Some manufacturers recommend equalization after 30 to 50 charge/discharge cycles, while others don’t recommend equalization at all; check with the battery manufacturer to be sure. Note: Battery equalization is for flooded-cell batteries only. Don’t attempt to equalize a gel-cell or AGM battery.
Last but not least, always make sure the battery is properly secured, the terminals are clean and the connections are tight. An improperly secured battery can bang around on its tray, causing internal damage. Loose or dirty connections can cause starting or charging problems.
If the terminals are caked in whitish powder, it’s time for a thorough cleaning. Disconnect the battery, then mix about one part baking soda in four parts water and pour it over the terminals. When the foaming subsides, rinse well with water, and the terminals should be clean. Mix another batch, and dip the connectors (terminals), one at a time. Dry everything thoroughly, reconnect the terminals and apply a small amount of grease or commercial terminal protectant to the connections to help retard oxidation.
Battery technology continues to evolve, and advances in lithium-ion engineering may completely upend the industry eventually. But for now, lead acid is still the mainstay of the RV market. It is important to pick the right product for the application and then pay attention to it over the years.
Like one battery manufacturer says in its literature, “It’s not always blue skies and open roads. Be ready.”
An Abbreviated History Of Batteries
- 1800: Italian physicist Alessandro Volta makes the first battery, the voltaic pile, using stacks of zinc, copper and saltwater-moistened cardboard.
- 1859: French physicist Gaston Planté comes up with the lead-acid battery that we are all familiar with as a device for starting vehicles.
- 1866: French chemist Georges Leclanché creates what evolves into the dry-cell battery. It’s much cheaper to construct and more robust.
- 1896: Cleveland’s National Carbon Company (later the Eveready Battery Company and today known as Energizer) makes the first commercially available battery, the 1.5-volt Columbia.
- 1900s: Thomas Edison improves the car battery, making it lighter and cheaper to manufacture. However, several missteps lead to his battery missing out on powering electric-starter motors on vehicles, which come to prominence around 1912.
- 1960s: German engineers come up with a spill-proof lead-acid gel-cell battery. The batteries contain sulfuric acid mixed with silica powder to form a gel-type substance.
- 1970s-’80s: The lead-acid car battery continues to be refined with absorbent glass mat (AGM) technology. The acid is not mixed with a gel, but instead microfibers keep the acid contained. Internal ventilation systems prevent spilling.
- 2000s: Lithium-ion batteries become popular for use in laptop computers, mobile phones, digital cameras and toys, as well as in electric cars and golf carts. They are still prohibitively expensive for use in an RV.
While it might seem on the surface that a product made of lead and acid would be a nightmare for recycling, the reality is quite the opposite. About 98 percent of all battery lead is recycled. Compare that to 55 percent of aluminum cans, 45 percent of newspapers, 26 percent of glass bottles and 26 percent of tires. Being first in class for recycling is the result of a closed-loop life cycle; a brand-new battery actually contains 60 to 80 percent recycled lead and plastic. Every time a battery is discarded, it is sent to a permitted recycler where the lead and plastic are reclaimed using strict environmental controls and then sent to a new battery manufacturer.
For More Information
Deka (East Penn)
610-682-6361 | www.dekabatteries.com
678-566-9000 | www.exide.com
866-842-5368 | www.interstatebatteries.com
909-599-7816 | www.lifelinebatteries.com
800-538-3627 | www.odysseybattery.com
888-867-8462 | www.optimabatteries.com
Trojan Battery Company
800-423-6569 | www.trojanbattery.com