By Greg Illes
Sometimes batteries seem ridiculously simple — we tend to see them as either working or dead. But there is way more than meets the eye in this 2,000-year-old technology.
RV batteries are made with lead plates interleaved with lead-dioxide plates. The plates are immersed in sulfuric acid, and the electrochemical reaction creates the battery effect. The whole bundle is wrapped up in a big plastic box with the electrical terminals on top.
As current is drawn from the battery, a chemical change occurs which causes both plates to begin to change into lead-sulfate. Normally when the battery is recharged, the lead-sulfate layer is converted back into lead and lead-dioxide.
This is where a major wrinkle arises. After extended use or even prolonged storage, some of that lead-sulfate begins to change from a fine-grained powder-like state into crystals. The crystalline structure prevents the lead-sulfate from changing back into lead and lead-dioxide, and the battery is described as “sulfated.” This is literally the beginning of the end of a battery’s life. When enough sulfation builds up, the battery plates become increasingly unable to perform their function — the battery becomes a very expensive, acid-filled boat anchor.
Because a battery in storage has a self-discharge component, it is common to find heavy sulfation occurring in fresh batteries after extended storage. Frequent discharge/recharge cycles are actually good for a battery because it does not provide time for the sulfate crystallization to occur. You can avoid the worst of sulfation influences by keeping batteries fully charged as much as possible, and never storing a discharged battery.
Once sulfated, batteries at one time were relegated to the recycle bin. However, there are now affordable devices which deliver a specialized pulse charging current. These battery chargers and maintainers (sometimes called desulfators) are sold by a number of vendors. A predominant player in this area is BatteryMINDer®, providing multiple models priced from $50-$150. See Amazon.com and automotive websites for details and reviews.
Keeping your batteries connected to a desulfator while stored is one of the best methods to prolong battery life, not to mention that it will keep your batteries at full charge for your next use.
For a lot more detail on batteries, there’s a terrific write-up in Wikipedia.