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Archive for Category Batteries
1. Solar 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. Deep cycle batteries are designed to be discharged down as much as 80% time after time. The major difference between a true deep cycle battery and others is that the plates are SOLID Lead plates - not sponge. This gives less surface area, thus less instant power like starting batteries need. Although these can be cycled down to 20% charge.
A lead-acid battery is composed of plates immersed in sulfuric acid. Each plate has a grid upon which is attached the active material (lead dioxide on the negative plates, pure lead on the positive plates.) Negative plates are all connected together, as are all of the positive ones. When the battery is discharged, 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.
What are volts?
It is the units of Potential difference across which a current flows.. The voltage of a battery depends on the number of cells. Each lead acid cell has 2 volts.
Recycling of Lead Acid Batteries
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.
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.
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 Battery
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.
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%.
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.
Necessity of Equalization Charge
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 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.
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.
- 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
- Donot add new electrolyte (acid)
- Donot use unregulated high output battery chargers to charge batteries
- Donot disconnect battery cables while the engine is running (your battery acts as a filter)
- Donot put off recharging batteries
- Donot add tap water as it may contain minerals that will contaminate the electrolyte
- Donot discharge a battery any deeper than you possibly have to
- Donot let a battery get hot to the touch and boil violently when charging
- Donot mix size and types of batteries
2. Solar Market - Vanadium Flow Batteries
Solar Power Costs have surely come down over the past few years-but has a bottle neck- The storage issue- i.e. the cost of batteries. Photo Voltaic Energy is intermittent, and needs to be stored. Bringing down the installed cost of solar power systems is half the challenge. Headway needs to be made in bringing down the cost of batteries for energy storage and other technologies that make solar (and wind, for that matter) cost effective and reliable.
Flow batteries refer to the charge generated as two fluids flow adjacently.. They have a longer life ( no of cycles) and do not degrade over time as do lithium-ion batteries, for example. The said factors make flow batteries ideal storage devices. They can sit idle for long periods without losing their charge, and they can be revved up to speed almost instantly when called into action. Another key advantage is scalability, merely by enlarging the size of the storage tanks for the fluids.
Vanadium has emerged as a preferred base for flow batteries, because instead of two different substance a vanadium flow battery relies only on one: vanadium. That eliminates the cross-contamination issues that typically complicate flow battery design.
3. Garnet Ceramics for Lithium Batteries
Garnet Ceramics may be the future for lithium batteries (high-energy ). Scientists have found some exceptional properties in garnet, which could enable development of higher-energy battery designs. Researchers seek to improve a battery energy density by using a pure lithium anode (this metal offers the highest known theoretical capacity) in an aqueous electrolyte with the ability to speedily transport lithium.
Scientists tend to believe that this would be an ideal separator material. Many new generation batteries use these two features [lithium anode in aqueous electrolyte], but integrating both into a single battery, poses a problem, because the water is very reactive with lithium metal. The reaction is very violent, which is why you need a protective layer around the lithium. Battery designers can either use a solid electrolyte separator to shield the lithium, but options are limited. LAPT or LISICON, which are often used as separators of choice, tend to break down under normal battery operating conditions. Researchers have endlessly searched for a suitable solid electrolyte separator material for years. The requirements for this separator material are very strict. It has to be compatible with the lithium anode, due to its (lithiums) reactivity, as well as be stable over a wide pH range. Lithium batteries are known to have an alkaline environment. The researchers used a technique called atomic resolution imaging to monitor structural changes in LLZO when immersed in a range of aqueous solutions. It was observed that the compound remained structurally stable over long periods in a wide range of pH (across neutral and extremely alkaline environments). In lithium-air batteries, researchers have tried to avoid the degradation of the separator by diluting the aqueous solutions, thereby rendering the batteries heavier and bulkier.