Originally Posted By: ram_man
Maintenance-free generally means that you don't have to add water to the battery. However, a battery exposed to severe overcharged conditions will gas and use water, resulting in premature battery failure. In addition, it is always a good idea to visually inspect your battery for corrosion. Using battery anti-corrosion treatment is always a good idea for best performance. It is also important to remember that your battery is part of the electrical system. When inspecting your battery you should check related components. Replace if necessary.
also there are some batteries that have removable caps maintenance batteries do. or low maintenance batteries.
maintenance free however shouldn't be messed with. a lot of people will take a screw driver to pop the top off and on some batteries that breaks a seal and damages the vent and will cause more gas to escape. I do believe the majority of people shouldn't do it. most people do not understand batteries well enough to do it. I feel similarly about brakes to. a lot of people can change drum brakes but cannot explain what each piece does. if you cannot explain each part you shouldn't mess with it.
btw where I live we don't see many exide batteries I haven't seen one in a very long time.
also I didn't see that you put agm they are different than gel though do behave similarly. I'm not that all but most optima batteries shouldn't be fast charged and jump starting is frowned upon.
Do you know why they (maintenance free batteries) dont need water?
Even AC Delco says that their professional battery is "virtually" maintenance free.
http://www.acdelco.com/parts/batteries/
VRLA has a valve set to a specific release pressure, and wicked electrolyte, these really are maintenance free, as you cannot break the seal nor can you really re-wick electrolyte.
Flooded batteries can all be maintained. The addition of excess electrolyte compensates for loss, and calcium or selenium-rich lead acid batteries offer reduced gassing under use and float, as compared older antimony type strengthened lead grids. Perhaps vent caps versus threaded caps hold pressure differently, but the name of the game always is RECOMBINATION. Some batteries even have a catalyst inside to help it. VRLA is the best in this respect, as the seals really maintain all H and O to recombine naturally.
Gel and VRLA are quite different in terms of build design and capabilities, this includes charge and float voltages.
You do realize that lead acid batteries ALL gas, right? Based upon Gibbs free energy, the electrolysis voltage is around 1.5V practically speaking. To get any real amount of electrolysis though, somewhere around 2.4V/cell is necessary.
Creating a long diffusion path and reasonably sealed caps will allow most of the gas to recombine at reasonable charge rates - alternators dont typically fast charge or fully charge batteries. Of course the only way to prevent loss is a really sealed battery, but the "maintenance free" batteries do well enough because practically speaking, the gasses dont leave fast enough with the little pressure, given headspace in the battery.
Short circuiting or rapidly overcharging a vrla/gel cell can blow the vent, which is not resettable (AFAIK), and then will result in more rapid dryout. These cells donthold excess electrolyte, in fact, they hold a lot less, so that's why they dont want careless folks jumping them or doing other stuff.
ram_man, it is REALLY great that youre learning, and sharing the insight that youre pulling from your classes, but it is important to discern practicality from what is taught, and also why certain things are taught certain ways. Its a good discussion overall, and Im glad we are having these.
