Source:
https://www.batterystuff.com/kb/
The Lead Acid battery is made up of plates, lead, and lead oxide (various other elements are used to change density, hardness, porosity, etc.) with a 35% sulfuric acid and 65% water solution. This solution is called electrolyte, which causes a chemical reaction that produce electrons. When you test a battery with a hydrometer, you are measuring the amount of sulfuric acid in the electrolyte. If your reading is low, that means the chemistry that makes electrons is lacking. So where did the sulfur go? It is resting on the battery plates and when you recharge the battery, the sulfur returns to the electrolyte.
Sulfation is the main cause of battery failures
Batteries develop sulfation each time they are used (discharged – recharged). If they are overcharged, undercharged or left discharged for just a few days, they will rapidly develop sulfate. This condition can be exacerbated with smaller lead acid batteries, such as motorcycle batteries. Even when stored fully charged, sulfate will form without a frequently applied maintenance charge. It must be charged enough to prevent the battery from dropping below 6.2 Volts or 12.4 Volts (2.07 volts / cell). Using or storing batteries in temperatures above 75 °F / 24° C accelerates the rate of self-discharge and increases sulfation dramatically.
Common causes of sulfation are:
- Batteries sit too long between charges. As little as 24 hours in hot weather and several days in cooler weather.
- Battery is stored without some type of energy input.
- Undercharging of a battery to only 90% of capacity will allow sulfation of the battery using the 10% of battery chemistry not reactivated by the incompleted charging cycle.
- Heat of 100 plus F., increases internal discharge. As temperatures increase so does internal discharge. The discharge rate doubles, as does sulfation, for every 10 °F / ~6 °C rise above room temperature.
- Low electrolyte level – battery plates exposed to air will immediately sulfate.
- Incorrect charging levels and settings.
- Cold weather is also hard on the battery. The chemistry does not make the same amount of energy as a warm battery. A deeply discharged battery can freeze solid in sub zero weather.
- Parasitic drain is a load put on a battery with the key off.
Battery maintenance: cable connections need to be cleaned and tightened as battery problems are often caused by dirty and loose connections. A serviceable battery needs to have the fluid level checked. Use only mineral free water, Distilled is best as all impurities have been removed, and there is nothing left that could contaminate your cells. Don’t overfill battery cells especially in warmer weather because the natural fluid expansion in hot weather can push excess electrolytes from the battery. To prevent corrosion of cables on top post batteries use a small bead of silicone sealer at the base of the post and place a felt battery washer over it. Coat the washer with high temperature grease or petroleum jelly (Vaseline), then place cable on the post and tighten. Coat the exposed cable end with the grease. Most people don’t know that just the gases from the battery condensing on metal parts cause most corrosion.
A VRLA battery (valve-regulated lead-acid battery), more commonly known as a sealed battery (SLA) or maintenance free battery, is a type of lead-acid rechargeable battery. Due to their construction, the Gel and AGM (absorbed glass fibre) types of VRLA can be mounted in any orientation, and do not require constant maintenance. The term “maintenance free” is a misnomer as VRLA batteries still require cleaning and regular functional testing.
The underlying fault with all lead acid batteries is the requirement for an excessively long charge time arising from a two-stage process: bulk charge and float charge. All lead acid batteries; irrespective of whether being VRLA Flooded, Gel, AGM & conventional flooded types are quick to charge to 70% of capacity within 2 or 3 hours, but this technology requires another 9 to 10 hours to “float charge” after the initial charge. If users fail to float charge, lead acid battery-type capacity is dramatically reduced. All types have a memory in that every time a user charges to less than 100% charge, battery capacity is shortened. A lead acid battery could reach 4,600 cycles if it were kept on a shelf and kept at the right state of charge. To ensure a life of 8 years, a lead acid battery should be kept at full charge when stored (or dry), and, when working, kept at depth of discharge of less than 20%. In addition, it’s discharge rate should be not more than three hours and its charge rate should be not more than three hours and it should be float charged properly. With less careful use, a lifetime of two to three years or 700-800 cycles might be expected, dependent upon the use environment.
Corrosion of battery posts/terminals
Cause 1: galvanic corrosion
Galvanic corrosion is caused by the potential difference between metals that come into contact with each other, in this case the material of the battery post and the cable connector. White corrosion usually consists of lead or zinc crystals or, if the connections are made of aluminum, of aluminum sulphate. If the connections are copper, the corrosion will usually consist of blue crystals. Very often the corrosion consists of a combination of white and blue crystals: white because of the lead in the terminal and blue by the copper in the cable. This kind of corrosion can be prevented by treatment with a terminal protector spray. If the corrosion has already occurred, first clean with a terminal cleaner. Also clean the cable connectors material and check for damage: a smooth, well-connected surface is important for good electrical conduction.
Cause 2: electrolytic corrosion
If the battery contains too much electrolyte (above the maximum level or it has been refilled in discharged state) thermal expansion can cause the acid to come out through the ventilation openings .This will come into contact with the terminals and connections and thus cause corrosion. This problem can be prevented by filling the battery with care.
Cause 3: atmospheric corrosion
Another cause can be found in the sulfuric acid vapors that occur during overcharging and can, in combination with poor ventilation, affect the battery poles and connections. The solution is of course a good charging regime and adequate ventilation.