Battery manufacturers listen to their customers and supply them with what they demand. About 30 years ago, a lot of customers said "I.'m too lazy to pull the caps off battery cells occasionally and check the electrolyte level and add water if necessary". The battery makers responded by developing "maintenance-free" batteries with sealed cell groups. They didn't work as well, or last as long as conventional batteries, but they were OK for most purposes. As long as a battery gets "exercised" occasionally, discharged about 25% or less and recharged, it will last longer and give better service than one that sits for weeks or months at a time without doing what it was designed to do- - - -provide a quick surge of starting current, and then get recharged over several minutes, or up to a few hours of vehicle operation before the next shutdown and restart. Extremes of operation at either end of the discharge/recharge envelope shorten battery life and/or require a different charging system or a "maintainer" to substitute for normal operation.
Recharging a low or dead battery and "maintaining" one that sits idle for extended periods requires different equipment. Trying to multi-task where battery charging is concerned doesn't accomplish either job as well as it could be done with dedicated equipment for both tasks. Most battery users don't know (or care) what's actually going on inside a battery- - - -they just want the thing to work right every rime, with no preventive maintenance whatsoever!
Jerry
