A lead-acid battery is composed of a series of plates immerse in a solution of sulfuric acid. Each plate consists of a grid upon which is attached the active material (lead dioxide on the negative plates, pure lead on the positive plates.) All of the negative plates are connected together, as are all of the positive plates. When the battery is discharged (when it is subjected to an electrical load), acid from the electrolyte combines with the active plate material. This releases energy and converts the plate material to lead sulfate. The chemical reaction between constituent parts of the electrolyte and the spongy lead of the negative plates and The lead dioxide at the positive plates turns the surface of both plates into lead sulphate. As this process occurs the hydrogen within the acid reacts with the oxygen within the lead dioxide to form water. The net result of all this reaction is that the positive plate gives up electrons and the negative plate gains them in equal numbers, thereby creating a potential difference between the two plates. The duration of the reactions producing the cell voltage is limited if there is no connection between the two plates and the voltage will remain constant.
Different Types of Batteries:
Basically there are two types of batteries, starting (cranking), and deep cycle (marine/golf cart/Fork-lift trucks). The starting battery (SLI starting lights ignition) is designed to deliver quick bursts of energy (such as starting engines) and have a greater plate count. The plates will also be thinner. The deep cycle battery has less instant energy but greater long-term energy delivery. Deep cycle batteries have thicker plates and can survive a number of discharge cycles.
What are volts?
It is the units of force or pressure of electric current. The voltage of a battery depends on the number of cells. Each lead acid cell has 2 volts.
What is meant by "specific gravity" of battery electrolyte?
It is the weight of the sulfuric acid-water mixture compared to an equal volume of water. Pure water has a specific gravity of 1.
Are lead acid batteries recyclable?
Lead acid batteries are 100% recyclable. The plastic containers and covers of old batteries are neutralized, reground and used in the manufacture of new battery cases. The electrolyte can be processed for recycled wastewater uses. In some cases, the electrolyte is cleaned and reprocessed and sold as battery grade electrolyte. In other instances, the sulfate content is removed as Ammonia Sulfate and used in fertilizers. The separators are often used as a fuel source for the recycling process.
What is the difference between a Cell and a Battery?
Strictly, an electrical "battery" is an interconnected array of one or more similar "cells". A car battery is a "battery" because it uses multiple cells. Multiple batteries or cells may also be referred to as a battery pack as a set of multi-cell 12 V batteries in an electric vehicle. A 12 Volt monoblock battery consists of 6 cells, but a plante’ or 2 Volt tubular battery is a battery though it consists of a single cell.
What is Battery capacity?
The capacity of a battery to store charge is often expressed in ampere hours (1 Ah = 3600 coulombs). If a battery can provide one ampere (1 A) of current (flow) for one hour, it has a real-world capacity of 1 Ah. If it can provide 1 A for 100 hours, its capacity is 100 Ah.
Battery manufacturers use a standard method to determine how to rate their batteries. The battery is discharged at a constant rate of current over a fixed period of time, such as 10 hours or 20 hours, down to a set terminal voltage per cell. So a 100 ampere-hour battery is rated to provide 5 A for 20 hours at room temperature. The efficiency of a battery is different at different discharge rates.
What is Battery lifetime & how it varies?
Rechargeable batteries can be re-charged after they have been drained. This is done by applying externally supplied electrical current, which causes the chemical changes that occur in use to be reversed. Devices to supply the appropriate current are called chargers or rechargers.
Temperature Effects on Batteries
Battery capacity (how many amp-hours it can hold) is reduced as temperature goes down, and increased as temperature goes up. The standard rating for batteries is at room temperature 25 degrees C. Battery charging voltage also changes with temperature.
Plate thickness (of the Positive plate) matters because of a factor called "positive grid corrosion". The positive (+) plate is what gets eaten away gradually over time, so eventually there is nothing left - it all falls to the bottom as sediment. Thicker plates are directly related to longer life. Most industrial deep-cycle batteries use Lead-Antimony plates rather than the Lead-Calcium used in AGM or gelled deep-cycle batteries. The Antimony increases plate life and strength, but increases gassing and water loss.
Cycles vs. Life
A battery "cycle" is one complete discharge and recharge cycle. It is usually considered to be discharging from 100% to 20%, and then back to 100%. Battery life is directly related to how deep the battery is cycled each time. If a battery is discharged to 50% every day, it will last about twice as long as if it is cycled to 80% DOD. If cycled only 10% DOD, it will last about 5 times as long as one cycled to 50%.
Do lead acid batteries discharge when not in use?
Yes. All batteries, regardless of their chemistry, will self-discharge even when no load is present. At a temperature of 27 degrees C, a lead acid battery will self-discharge at a rate of approximately 4% a week. A battery with a 125 amp-hour rating would self-discharge at a rate of approximately five amps per week.
A rule of thumb is to ALWAYS keep your batteries fully charged while not in use!
Charging Lead-Acid Batteries
A multi-stage charger first applies a constant current charge, raising the cell voltage to a preset voltage, takes about 5 hours and the battery is charged to 70%. During the topping charge, the charge current is gradually reduced as the cell is being saturated. The topping charge takes another 5 hours and is essential for the well being of the battery. If omitted, the battery would eventually lose the ability to accept a full charge. Full charge is attained after the voltage has reached the threshold and the current has dropped to 3% of the rated current or has leveled off. The final is the float charge, which compensates for the self-discharge.
What is an Equalization Charge & Why it is Necessary?
In any cyclic application, a series of batteries will always need to be equalized from time to time in order to ensure that the battery cells remain at the same voltage throughout the pack. During the charge cycle the voltages of the different batteries will very. In order to bring them all to the same level it is necessary to give some a slight overcharge in order to bring the other up to full charge. Equalization is done by allowing the voltage to rise while allowing a small constant current to the batteries. The voltage is allowed to rise above the normal finish voltage in order to allow the weaker batteries/cells to draw more current.
Calculating the battery runtime
A battery can either be discharged at a low current over a long time or at a high current for only a short duration. At 1C, a 10Ah battery discharges at the nominal rating of 10A in less than one hour. At 0.1C, the same battery discharges at 1A for roughly 10 hours. While the discharge voltage of lead acid decreases in a rounded profile towards the end-of-discharge cut-off. The relationship between the discharge time (in amperes drawn) is reasonably linear on low loads. As the load increases, the discharge time suffers because some battery energy is lost due to internal losses. This results in the battery heating up.
What is battery Sulphation and when does it occur?
Sulphation (or Lead Sulfate) is the formation of hard crystals on the plates of your battery. Initially, the lead sulfate coating is soft, thin and easily reconverted into lead and sulfuric acid when battery is recharged. It is important to remember, the longer your battery remains discharged, the more it will begin to form hard crystals of lead sulfate…RECHARGE YOUR BATTERY AS SOON AS POSSIBLE!
Can I hook different batteries in parallel?
No, when hooking batteries together in parallel, they should be of identical make and model and similar age.
When should I add water to my batteries?
How often use and recharge your batteries will determine the frequency of watering. It is best to check your battery water level frequently and add distilled water when needed. Never add tap water to your battery. Tap water contains minerals that will reduce battery capacity and increase their self-discharge rate. And never add acid. Only distilled or de-ionized water should be added to achieve the recommended electrolyte levels.
What are the reasons for failure of batteries?
Self discharge of plates and premature capacity loss; excessive float charge current and improper polarization of plates; shorts through separator, mossing or dendrite growth; overcharging of battery from high current and subsequent excessive gassing; excessive heat and loss of water; antimony transfer; low cold cranking performance; poor charge acceptance; inadequate high rate discharge performance.
Battery Maintenance Procedure
Maintenance is an important issue. The battery should be cleaned using a baking soda and water mix; a couple of table spoons to a pint of water. Cable connection needs to be clean and tightened. Many battery problems are caused by dirty and loose connections. A serviceable battery needs to have the fluid level checked. Use only mineral free water. Distilled water is best. Don't overfill battery cells especially in warmer weather. The natural fluid expansion in hot weather will push excess electrolytes from the battery. To prevent corrosion of cables on top post batteries use a small bead of silicon 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 folks don't know that just the gases from the battery condensing on metal parts cause most corrosion.
Think Safety First.
Do read entire tutorial
Do regular inspection and maintenance especially in hot weather.
Do recharge batteries immediately after discharge.
Do buy the highest RC reserve capacity or AH amp hour battery that will fit your configuration.
Don't add new electrolyte (acid).
Don't use unregulated high output battery chargers to charge batteries.
Don't disconnect battery cables while the engine is running (your battery acts as a filter).
Don't put off recharging batteries.
Don't add tap water as it may contain minerals that will contaminate the electrolyte.
Don't discharge a battery any deeper than you possibly have to.
Don't let a battery get hot to the touch and boil violently when charging.