The days of having to run the engine of your vehicle just to keep the vacuum tubes filaments of your mobile unit from draining the battery dry are gone but the necessity of keeping the battery in good condition are not.
The oldest modern rechargeable battery is the lead-acid battery invented by French physicist Gaston Planté in 1859. Though it has been around for almost 150 years the lead-acid batteries still has a lot of advantages over other types of rechargeable batteries. They can be partially drained or fully drained and recharged over many times without losing their ability to go through the cycle again. This is why they are still the preferred battery to use in the automobile. You start your car and the battery is partially drained by the starter current. When the engine is running the charging system rebuilds the charge and maintains it.
Other rechargeable batteries ,nickel cadmium, nickel metal hydride, lithium ion, and lithium ion polymer , would cost a fortune if constructed to sufficient size to start the engine and they would not stand up to that constant small drain and recharge over and over like the lead-acid battery does. Other rechargeable battery only has so many charges whether it starts from fully drained or just a partial drain and then it just wont take much of a charge and must be replaced but the lead-acid battery doesn’t seem to care how many times it is charged.
The lead-acid battery consists of lead (Pb) and lead Oxide (PbO2) plates submersed in a solution of water (63%) and sulfuric acid (37%). During discharge both electrodes surfaces turn into lead sulfate while the electrolyte loses some of its sulfuric acid to form the lead sulfate leaving a higher percentage of water in the solution. During this process electrolysis breaks down some of the water into hydrogen and oxygen an explosive mixture. That is why the lead acid battery must be operated with good ventilation. Evaporation also removes some of the water but the sulfuric acid does not evaporate significantly thus for all practical purposes only pure water will be lost during normal operation.
As the water level lowers it will need to be replaced. Pure water is lost pure water should be used to replace it. If there are impurities in the water they will change the chemical properties of the electrolyte and thus change the effectiveness of the battery. The sulfuric acid will breakdown many to the particles contained in impure water which will reduce the amount of acid contained in the electrolyte. It can also lead to an increase in resistance in the battery decreasing its performance and increasing its temperature during operation. Increased temperature increases the rate of evaporation which increases the frequency of necessary water replacement which, if pure water is not used, increases the resistance.
Replacing the water with distilled water is the only way to be assured that the chemical properties of the electrolyte will remain constant.
I strongly recommend that when you need to replace the water in your battery use distilled water which you have purchased and you know is distilled and add the water yourself or allow someone you trust to replace it for you. Almost every mechanic, service station attendant, or oil change specialist will replace the battery water with tap water because they either do not understand the importance or they don’t care and they want to save the pennies it costs for distilled water.
The effects of impure water will probably not be immediately noticeable but it will reduce the life and efficiency of the battery. When a lead-acid battery is properly maintained they will normally give you a warning when they are wearing out but batteries that have not been maintained properly more times then not will deteriorate more rapidly without warning leaving you stranded and having to call for assistance.
Should I tell the horror stories of jump starting? No I think I will save that for another time.