What’s a Battery?
The first documented battery that used two dissimilar metals with an electrolyte between them was invented in 1800. It became known as the voltaic pile after the inventor Volta. The voltaic pile consisted of copper and zinc discs piled on top of each other, separated by a layer of cloth or heavy paper soaked in a brine solution. Unlike the Leyden jar from much earlier attempts at energy storage, the voltaic pile produced a continuous and stable current level. The first rechargeable lead/acid battery for commercial use was invented by a French physician Gaston Planté in 1859.
The lead acid battery is made up of plates, lead and lead oxides with various other elements to change the density, hardness, porosity, and electron flow. Typically, the electrolyte solution will contain 35% sulfuric acid and 65% water. This solution causes a chemical reaction that produce electrons. As the battery charges, the sulfuric acid becomes heavier, causing the electrolytes specific gravity (SG) to increase. As the state of charge (SOC) decreases through discharge, the sulfuric acid is pulled from the electrolyte and binds to the internal plates, forming lead sulfate. The density of the electrolyte becomes lighter and more water-like, and the SG is reduced. Sulfation of a Battery starts when the specific gravity falls below 1.225 or the voltage measures less than 12.4 (12v Battery) or 6.2 (6 volt battery). Sulfation hardens the battery plates reducing the electron flow and eventually will reach a point that it cannot be restored by recharging. Battery life varies depending on the application as well as how it’s used. Anywhere from 6 months to 48 months is a typical life of a battery, yet statistically, less than 30% of automotive batteries ever reach the 48-month mark.
The specific gravity also varies according to battery type. Deep-cycle batteries use a denser electrolyte with an SG of up to 1.330 to get maximum runtime; aviation batteries have a SG of 1.285; traction batteries for forklifts are at 1.280; starter batteries come in at 1.265 and stationary batteries are at a low 1.225.
Basically there are two types of batteries, starting (cranking) and deep cycle (marine-golf cart-forklift).
The starting battery is designed to deliver a high energy output for a short amount of time and generally have a greater plate count. The plates will also be thinner (more surface area) and have somewhat different material composition. The deep cycle battery provides less surge energy but a greater long-term delivery. Deep cycle batteries have thicker plates and can be discharged way below their full charge level and recharged back to full. Car (starting) batteries don’t have that capability. (Starting batteries should not be used for deep cycle applications.)
Cold Cranking Amps (CCA) - is a measurement of the number of amps a battery can deliver at 0°F for 30 seconds and not drop below 7.2 volts. So a high CCA battery rating is good especially in cold weather. Cranking Amps (CA) - is measured at 32°F. This rating is also called marine cranking amps (MCA). Hot cranking amps (HCA) is seldom used any longer but is measured at 80°F. Reserve Capacity (RC) - is a very important rating. This is the number of minutes a fully charged battery at 80°F will discharge 25 amps until the battery drops below 10.5 volts. Amp Hour (AH) - is a rating usually found on deep cycle batteries. If a battery is rated at 100 amp hours it should deliver 5 amps for 20 hours, 20 amps for 5 hours, etc.
Battery Maintenance is an important issue. Cable connections need to be clean and tight. 70% of battery problems are caused by dirty and loose connections. Distilled water is best; tap water is loaded with chemicals and minerals that are harmful to your battery, but not as bad as no water at all. Don't overfill battery cells especially in warmer weather. (The fluid will expand in the warmer temperatures as well as when it is fully charged.) The gases produced from the battery charging will escape out the vent holes in the caps and condense on the metal parts and cause corrosion. Using corrosion prevent pads, sprays, or grease (Vaseline works well) on or around the terminals will reduce the buildup. Also, make sure to keep the hold down brackets painted and clean to prevent them from deteriorating. To remove any corrosion or acid build up there are several over the counter sprays and solutions that work quite well. I still prefer baking soda and water as a cleaning agent. Some mechanics like to use a Cola as a cleaner, never cared for that method myself, too messy. Cleaning the corrosion build up is simple chemistry, a base solution reacts with an acid. The idea is to remove the acid and corrosion without damaging the base metals. Start with a baking soda and water mixture poured over the area, then rinsed thoroughly, dried, and apply some form of preventive measure to avoid any build up in the future. This would include repainting any metal brackets or exposed metal in the surrounding area as well.
Charging and Testing
A freshly charged battery is not a good candidate for checking the charge level. There will be a surface charge that hovers on the “surface” of the cells and is not part of the storage level of the battery itself. If the battery has been setting for at least 6 hours you may begin testing. To remove the surface charge the battery must experience a load of roughly 15 to 20 amps for about 3 minutes. Turning on the headlights (high beam) will do the trick. After turning off the lights you are ready to test the battery. When you’re testing a battery with a hydrometer you are actually measuring the amount of sulfuric acid in the electrolyte. If the reading is low, there’s not enough sulfuric acid in solution. Recharging the battery creates a chemical reaction to break up the sulfated bond between the plates and the acid which allows the sulfuric acid to go back into the solution. State of ChargeSpecific GravityVoltage - 12VVoltage - 6V Discharged 1.120 11.90 6.0 Load Testing is another way of determining the condition of the battery. Using a carbon pile type battery load tester, apply a load equal to one half the batteries CCA level for 15 seconds. A good battery will not fall below 9.6 volts during the test and when the 15 seconds has passed the battery should return to the its original starting voltage that it had before the test. The newer “non-carbon pile” battery testers work entirely different, and are highly accurate as well. They not only can spot a marginal battery much quicker but also take in account the temperature and estimated battery life when calculating the overall condition. Interstates ED-18 for example has a digital screen with all the functions clearly shown as well as a printer built into it.
New Lead Acid Systems
Lead acid batteries continue to be the most viable source of energy for most automotive applications. Some improvements have been made and some claims are so promising that they sound too good to be true. Here are a few of the new lead acid developments that researchers are working on. Firefly Energy, Altraverda Bipolar, Axion Power, CSIRO Ultrabattery, and EEStor systems and designs just to name a few. Most of these developments are based on ceramics and other exotic metals and chemical combinations. Most of these “in the testing stages” ideas still use some form of lead acid based electrolyte solution. I wouldn’t be surprised to see a new version of the wet cell battery with a longer charge rate and a longer life span for the automotive industry. The advancements in energy storage make it possible for new designs and new systems. Just think where we would be without the ability to store energy in a portable device such as a battery.