BATTERY TYPES

摘要

FLOODED BATTERIES are filled with a solution of sulfuric acid called free electrolyte. While some flooded batteries are "sealed," or "maintenance-free," the vast majority, and particularly those designed for marine applications, can be maintained by the addition of distilled water. These batteries can withstand repeated or chronic overcharging; when this occurs, they bubble or gas, sometimes vigorously, as they emit hydrogen. Gassing is normal, to an extent; it's part of the chemical process that occurs in flooded lead-acid batteries and is the reason why they periodically require water (hydrogen being one of the constituents of water). Under normal circumstances, even if you can't hear them doing it, flooded batteries emit hydrogen gas. While these batteries can endure overcharging, it should be avoided at all costs because it shortens battery life and makes frequent watering necessary, and the by-product, hydrogen gas, is explosive. The primary weakness of flooded batteries, when compared to contemporary types that will be discussed in a moment, is that they are comparatively slow to charge and have a self-discharge rate of just under 1 percent per day at 80cF. Because their internal resistance (resistance is the opposition to the flow of current) is relatively high, there is a limit to how rapidly they can accept a charge, even if charging current is available in abundance.