Regular attention and proper use will give coach batteries extra life.
By Bill Hendrix, F761S
Investing a few minutes each month could double your RV battery’s life. However, batteries seem to be one of those things RVers commonly overlook until a problem arises. The greatest probability of shortened battery life lies with the flooded-cell lead-acid batteries. This style has a removable cap on each cell for replenishment of the water that escapes as vapor during the discharge and recharge cycle. Continuing to use the battery when the fluid (electrolyte) level is below the plates will invite a premature failure. The sealed-cell style of battery construction, as used in gel-cell and absorbed-glass-mat (AGM) batteries, does not require irrigation to maintain the electrolyte, but there are other things we must consider (more on that a little later).
As the flooded-cell battery recharges, the cells expel some electrolyte vapor along with hydrogen gas. The battery folks call this “gassing” or “venting.” The electrolyte vapor is composed of water and a bit of sulfuric acid. The amount of gassing is somewhat proportional to the rate of charge but accelerated by higher ambient temperatures. Here is where some maintenance is necessary. At least monthly, the fluid level in each cell should be checked. To do this, remove the caps and use a flashlight to see into each cell. The electrolyte should be above the top of the plates and at or just below the bottom of the cap hole. Use distilled water to refill the cells, and be careful not to overfill. An overfilled cell will discharge the overage as it expands during the discharge/recharge cycle.
While you have the compartment open, inspect the terminals, the battery cases, and the surrounding area for corrosion. The acidic vapor from gassing will condense on any cooler surface available. This is where corrosion starts “” normally around the battery terminals, connections, and virtually anywhere. Also look for any oily-appearing substance on the top of the battery case. This is battery acid mixed with dirt, and it has the potential to steal current from the battery if it leaches to a ground source. To illustrate its potential, use a voltmeter set on the 15-volt scale and take a voltage reading between the oily substance and the negative terminal. You will be “shocked” at the reading!
Before performing any maintenance, take precautions. Batteries can be very dangerous! Wear rubber gloves, a face shield, old clothing, and a plastic apron if you have one. Don’t use any metallic item in the cleaning process “” not even a metallic sprayer on the garden hose “” as a sudden grounding of the positive terminal can actually cause a battery to explode. Always remove the negative lead to frame ground first.
To neutralize any corrosion, sprinkle ordinary baking soda liberally on the top of the battery and any other affected surfaces. Use a plastic brush and a little water to scrub the soda around the terminals and the battery case. Sprinkle baking soda down around the bottom of the battery to take care of any acid there. Flush the area with water, but be aware that the runoff, although neutralized, might be considered hazardous waste and should be disposed of properly.
Treated felt discs and pads can be purchased to place under the battery terminals and battery, respectively. These pads will help neutralize the corrosion, but they need to be replaced periodically. After the terminals are thoroughly dried, give them a spray coat of battery terminal protector. The discs, pads, and terminal protector spray are available at most auto supply stores.
If you find a loose connection or if you replace a battery, be sure to clean the battery post and the inside of the connecting terminal to remove any oxidation normally caused by electrolysis between the two contact surfaces.
I believe that a big part of maintenance is the proper use of the batteries. By that I mean to refrain from repeatedly discharging to less than a 50 percent state of charge (12.2 volts) and to recharge to at least 85 percent (12.5 volts) as soon as possible. This also applies to gel-cell and AGM batteries, with a slight change in the voltage numbers. Any battery is subject to failure for a wide variety of reasons at any time, but with proper use and good maintenance, a much longer life can be expected.
For more detailed information on recharging, and state of charge, see the article “RV Batteries” in the January 2005 issue of Family Motor Coaching.