How Lead Acid Batteries Work
Here is a short run-through of how lead-acid batteries work. I’ll start with some basics and work my way up – hence the absence of an alphabetical order. Depending on your familiarity with the subject, you may want to scroll down more or less. hp compaq PA-1900-18H2 Adapter dell M70 Adapter
Voltage Voltage is an electrical measure which describes the potential to do work. The higher the voltage the greater its risk to you and your health. Systems that use voltages below 50V are considered low-voltage and are not governed by an as strict (some might say arcane) set of rules as high-voltage systems. Current Current is a measure of how many electrons are flowing through a conductor. Current is usually measured in amperes (A). Current flow over time is defined as ampere-hours (a.k.a. amp-hours or Ah), a product of the average current and the amount of time it flowed. Power Power is the product of voltage and current and is measured in Watts. Power over time is usually defined in Watt-hours (Wh), the product of the average number of watts and time. Your energy utility usually bills you per kiloWatt-hour (kWh), which is 1,000 watt-hours. What is a Lead-Acid Battery? A lead-acid battery is a electrical storage device that uses a reversible chemical reaction to store energy. It uses a combination of lead plates or grids and an electrolyte consisting of a diluted sulphuric acid to convert electrical energy into potential chemical energy and back again. The electrolyte of lead-acid batteries is hazardous to your health and may produce burns and other permanent damage if you come into contact with it. Thus, when dealing with electrolyte protect yourself appropriately! Deep Cycle vs. Starter Batteries Batteries are typically built for specific purposes and they differ in construction accordingly. Broadly speaking, there are two applications that manufacturers build their batteries for: Starting and Deep Cycle. As the name implies, Starter Batteries are meant to get combustion engines going. They have many thin lead plates which allow them to discharge a lot of energy very quickly for a short amount of time. However, they do not tolerate being discharged deeply, as the thin lead plates needed for starter currents degrade quickly under deep discharge and re-charging cycles. Most starter batteries will only tolerate being completely discharged a few times before being irreversibly damaged. Deep Cycle batteries have thicker lead plates that make them tolerate deep discharges better. They cannot dispense charge as quickly as a starter battery but can also be used to start combustion engines. You would simply need a bigger deep-cycle battery than if you had used a dedicated starter type battery instead. The thicker the lead plates, the longer the life span, all things being equal. Battery weight is a simple indicator for the thickness of the lead plates used in a battery. The heavier a battery for a given group size, the thicker the plates, and the better the battery will tolerate deep discharges. Some “Marine” batteries are sold as dual-purpose batteries for starter and deep cycle applications. However, the thin plates required for starting purposes inherently compromise deep-cycle performance. acer PA-1750-04 Adapter Compaq Presario V2000 Adapter Thus, such batteries should not be cycled deeply and should be avoided for deep-cycle applications unless space/weight constraints dictate otherwise. Regular versus Valve-Regulated Lead Acid (VRLA) Batteries Battery Containers come in several different configurations. Flooded Batteries can be either the sealed or open variety. Sealed Flooded Cells are frequently found as starter batteries in cars. Their electrolyte cannot be replenished. When enough electrolyte has evaporated due to charging, age, or just ambient heat, the battery has to be replaced. Deep-Cycle Flooded cells usually have removable caps that allow you to replace any electrolyte that has evaporated over time. Take care not to contaminate the electrolyte – wipe the exterior container while rinsing the towel frequently. VRLA batteries remain under constant pressure of 1-4 psi. This pressure helps the recombination process under which 99+% of the Hydrogen and Oxygen generated during charging are turned back into water. The two most common VRLA batteries used today are the Gel and Absorbed Glass Mat (AGM) variety. Gel batteries feature an electrolyte that has been immobilized using a gelling agent like fumed silica. AGM batteries feature a thin fiberglass felt that holds the electrolyte in place like a sponge. Neither AGM or Gel cells will leak if inverted, pierced, etc. and will continue to operate even under water. Battery Cells Battery Cells are the most basic individual component of a battery. They consist of a container in which the electrolyte and the lead plates can interact. Each lead-acid cell fluctuates in voltage from about 2.12 Volts when full to about 1.75 volts when empty. Note the small voltage difference between a full and an empty cell (another advantage of lead-acid batteries over rival chemistries). Battery Voltage The nominal voltage of a lead-acid battery depends on the number of cells that have been wired in series. As mentioned above, each battery cell contributes a nominal voltage of 2 Volts, so a 12 Volt battery usually consists of 6 cells wired in series. State of Charge The State of Charge describes how full a battery is. The exact voltage to battery charge correlation is dependent on the temperature of the battery. Cold batteries will show a lower voltage when full than hot batteries. This is one of the reasons why quality alternator regulators or high-powered charging systems use temperature probes on batteries. hp 239427-003 Adapter HP Pavilion dv6700 Adapter Depth of Discharge (DOD) The Depth of Discharge (DOD) is a measure of how deeply a battery is discharged. When a battery is 100% full, then the DOD is 0%. Conversely, when a battery is 100% empty, the DOD is 100%. The deeper batteries are discharged on average, the shorter their so-called cycle life.