The Critic,
Everyone knows to fill their battery with water, yet no one will advise on filling up batteries with acid because it is a very tricky business. I have done this for quite some time so I have seen nearly anything and everything when it comes to battery maintenance.
No matter what the battery says, maintenance free or not, every flooded battery will eventually loose water and will need replenishment. Water loss is due to several factors: natural evaporation, charging/ discharging as chemistries reverse, evaporation due to overheating/overcharging, and loss due to a fine mist that leaves the battery when charged rapidly with vent caps opened. The reason why batteries are called maintenance free is because your average driver will not know the difference, the manufacturer is hoping that the battery fails pre-maturely outside of its free warranty replacement thus ensuring more revenue and business.
Most lead acid batteries out there, even ones that seem to be perfectly closed, do have a one way vent which must open in case of overcharging. Overcharging causes lots of hydrogen and oxygen build up as the battery tries to get rid of excess energy by separating water into H2 and O2. If there were no vents, batteries would simply crack or explode due to the high internal pressures. This also holds true for gel batteries as well as Optima, and Exide Orbital batteries.
Many people tend to confuse gel batteries with Optima and Exide Orbital which are lead acid, they are not the average flooded type but have a sponge sandwiched between the positive and negative electrodes, hence the reason they can be mounted in any position. Gel batteries are not that popular dues to a major flaw, once overcharged excessive gassing pushes the gel substance away from the electrode permanently causing pre-mature failure. The total contact surface area in a battery between the plates and electrolyte or gel is what determines the actual power output as opposed to what the ratings says.
A fresh battery stars with a specific gravity of 1.280, usually referred to as 1280, the chemists here can correct me but I believe a 2 moral acid strength solution. What this means is that the acid + water (electrolyte) solution in the battery is 1.280 times heavier than the same amount of water which has a specific gravity of 1.000. The 1280 state is measured at 80F, I myself have a temperature compensated hydrometer so I can take correct readings in any temperature spectrum. As we proceed to discharge a battery, the acid will react with the positive and negative plates causing electrolyte to weaken. Discharging creates sulfates on your plates, these sulfate crystals eventually take up more and more real estate on the plates causing the battery to be weaken because there is less contact area with the acid and the plates. (just as in my gel battery reference)Your alternator or charger will then kick in to charge, forcing the sulfates to convert back into an active solution. Once a battery is fully charged it will return to a 1280 state and everyone is happy happy. This is the ideal world scenario, bare with me.
In the real world, as batteries are discharged, sulfate crystals grow and over time harden, hence the reason why batteries that sit for a long time become useless. As these crystals harden and grow, they have a tendency to expand, their expansion also forces the plate onto which they grow to expand, but the plate has already been sandwiched under pressure from the factory to avoid vibration so it has nowhere to expand. Now the plate begins to buckle, as it buckes the uniform surface on the plate cracks causing the crystals to fall to the bottom of the battery. A broken off crystal away from the plate does us no good as when current is introduced to charge the battery, the broken off crystals cannot react with the plate to be converted into active solution, thus our 1280 ideal will no longer be reached, a good reason why batteries should not be left in a discharged state for prolonged periods of time. Eventually when enough crystals settle at the bottom of a cell, they touch the bottom plates, shorting the cell and rendering a battery useless.
If heavily discharged batteries are charged with a high current, the build up of the crystals will cause high resistance, and high resistance will be dissipated by excess heat and gassing. This internal heat will cause excessive gassing, and excessive evaporation from the battery. Batteries that are overcharged (usually 14.40V and higher) will also dissipate excess energy into heat and excessive gassing. Excessive heat and/or excessive gassing or both tell us that a battery is charged faster than what it can handle at a given time, thus it is overcharged. In either case water will either evaporate, be converted into hydrogen and oxygen, or electrolyte will be forced out of the battery in a fine mist. One reason why those who have faulty charging systems refer to batteries as “boiled away” or “cooked away,” checking your battery level occasionally will give you a good idea of your charging system.
Chemistry also tells us that no chemical reaction is complete. When we react substances called reactants, a reaction takes place and we have the product reaction. Since this is also true for a battery if we were to discharge a perfectly charged battery at the 1280 state and forget about all the other problems that I have mentioned, charge it back up, we would never reach the 1280 state again. Hence the reason that no reaction is complete, now instead of a 100% reactants, we may have 99.9999% reactants, so inevitably some minute sulfate crystals will be left on the battery. Over time they will grow, harden and render the battery useless, even when regularly charged.
Hence the reason why your battery with a hydrometer showed an OK stare, so you left it alone because everything appeared to be normal. Then one day as the specific gravity decreased quite a bit, the eye changed colors because the electrolyte weakened. You added water further diluting the electrolyte solution, hence the reason why even after a refill, your battery showed a discharged state. Dilution of the electrolyte further caused the internal resistance to increase, thus soon after your battery probably died.
Now after looking at the basics of what happens in a battery, you may add acid as long as you have a hydrometer and know what it is that you are doing. I am able to buy battery acid (do not use industrial acid) already pre-diluted to 1260, I buy mine at Autozone for 5 bucks. This is made to fill the small motorcycle batteries but I use it for car purposes. With a good charging system the need to add more water or acid should be no more than 3-4 years at max which I consider to be the normal rate of evaporation. Everyone say DO NOT ADD ACID, just as I was told by everyone to change my oil every 3K miles, yet they assume that a battery will somehow be under ideal conditions all of its life, not the case here in the real world.
Lately I have gone away from the flooded vented type as contaminants introduced into the electrolyte will cause battery problems. I do like the Optima and Exide orbital batteries, I myself have the Exide Orbital (many here have reported at least on regular Exides low quality manufacturing causing premature failures) as it was much cheaper at the time of my purchase. Both have the one way vents, so it is hard for dust and other contaminants to get inside and cause any problems. I personally am done with flooded batteries as they leak through the vents no matter what, and the last thing which I need is acid corroding the body or the frame. But on occasion I do get a free one with which I can play, experiment or I do give advice to my fellow car friends either in person or here on BITOG.
So to sum it up, yes you can add acid, however do it in small quantities, do give the battery ample time to mix before taking a measurement (say over night to ensure accurate readings) and ALWAYS HAVE EYEs AND HANDS PROTECTED AT ALL TIMES.
To combat the aging of batteries due to inevitable sulfation build up, there are a couple of chargers that offer pulses which do break the hardened crystals and return them back into active solution. I myself have been for the past 5 years using and testing a much hated device here on this forum compared to a snake oil, yet I am not able to bash it in any way because from the measurements that I have performed on my batteries, it does what it claims. I have a couple of vehicles which have 9+ year batteries of all brands that I am currently testing and I shall see how long I will be able to have them going. My baby the Exide Orbital which I have mentioned here, is from the early days of 1999 when they first came out, it survived 1 car and is still going strong, I am interested to see when this puppy will die.
Hope my brief synopsis of battery chemistry made sense and that you have learned something as well. If in doubt or need some more clarifications, let me know.
