 
There are many things that can cause a battery to fail or drastically shorten its life.
One of those things is allowing a battery to remain in a partially discharged state. We talked about sulfate forming on the surface of the battery’s plates during discharge, and the sulfate also forms as a result of self-discharge. Sulfate also forms quickly if the electrolyte level is allowed to drop to the point that the plates are exposed. If this sulfate is allowed to remain on the plates, the crystals will grow larger and harden till they become impossible to remove through charging. Therefore, the amount of available surface area for the chemical reaction will be permanently reduced. This condition is known as “sulfation,” and it permanently reduces the battery’s capacity. A 20 amp hour battery may start performing like a 16 amp hour (or smaller) battery, losing voltage rapidly under load and failing to maintain sufficient voltage during cranking to operate the bike’s ignition system. This last condition is evident when the engine refuses to fire until you remove your finger from the start button. When you release the starter, the battery voltage instantly jumps back up to a sufficient level. Since the engine is still turning briefly, the now energized ignition will fire the spark plugs. In the next installment, we’ll see exactly why increased internal resistance due to sulfation causes less power to be delivered to the starter.
Deep discharging is another battery killer. Each time the battery is deeply discharged, some of the active material drops off of the plates and falls to the bottom of the battery case. Naturally, this leaves less of the stuff to conduct the chemical reaction. If enough of this material accumulates in the bottom of the case, it’ll short the plates together and kill the battery.
Overcharging is an insidious killer; its effects often aren’t apparent to the innocent purchaser of the ten-dollar trickle charger who leaves it hooked to the battery for extended periods. A trickle charger charges at a constant rate regardless of the battery state of charge. If that rate is more than the battery’s natural absorption rate at full charge, the electrolyte will begin to break down and boil away. Many a rider has stored a bike all winter on a trickle charger only to find the battery virtually empty in the spring. Also, since charging tends to oxidize the positive plates, continued overcharging can corrode the plates or connectors till they weaken and break.
Undercharging is a condition that exists on many Gold Wings. Your voltage regulator is set to maintain your system voltage at around 14 to 14.4 volts. If you’re one of those folks who rides the interstate highways with your voltmeter showing only 13.5 volts because you’re burning more lights than Macy’s Christmas display, you should be aware that that voltage is sufficient to maintain a charged battery but insufficient to fully recharge a depleted one. Remember, we said that gassing occurs when all or most of the lead sulfate has been converted back to lead and lead dioxide. The voltage at which this normally occurs, known as the gassing voltage, is normally just above 14 volts. If your system voltage never gets that high, and if you don’t ever compensate by hooking up to a charger at home, the sulfate will begin to accumulate and harden just as plaque does in your mouth. Consider a thorough occasional charging to be like a good job of flossing and brushing your teeth. If you practice poor dental hygiene, you can go to the dentist, and have him blast and scrape at the yucky stuff. When your battery reaches that stage, it’s curtains!
