9. Give the Classification of lead acid batteries. Describe the charge and discharge curves of lead acid batteries.

Lead acid batteries it is a type of most common batteries in our days. Main areas of application are: accumulator batteries for transports, emergency electric sources, backup power sources. Operating principle. In the discharged state both the positive and negative plates become lead(II) sulfate (PbSO4), and the electrolyte loses much of its dissolved sulfuric acid and becomes primarily water. The discharge process is driven by the conduction of electrons from the negative plate back into the cell at the positive plate in the external circuit. Negative plate reaction: Pb(s)+HSO−4(aq)→PbSO4(s) + H+(aq)+2e. Positive plate reaction: PbO2(s) + HSO−4(aq) + 3H+(aq) + 2e− → PbSO4(s)+2H2O. The total reaction can be written as Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(s) + 2H2O. Rated voltage produced by such a battery is 2 volts. Single batteries are connected in series to obtain higher voltage values. Example: a 12-volt battery consists of series-connected in a common housing, the six batteries. By construction, lead-acid batteries are maintenance-free and serviced. Serviced during operation requires some care (control level and electrolyte density). Maintenance-free - are airtight, operate in any position and does not require maintenance. There are the following basic types of lead-acid batteries, which can be used in stand-alone power supply systems: starter you know them well, require maintenance, and ventilation. They have high self-discharge. AGM - these sealed, maintenance-free batteries do not require a ventilation space for the installation. Cheap AGM type batteries work well in buffered mode, in the charging mode. This mode serves to 10-15 years. General purpose AGM batteries typically used in inexpensive ninterruptible Power Supply (UPS); UPS generally intended to crash, not to supply the load continuously. Therefore, given that they are usually in the offices there and put AGM batteries. Gel batteries more resistant to cyclic charge-discharge modes. Also, they seem to tolerate extreme cold. Reduced capacity with decreasing battery temperature is also less than other types of batteries. Gel batteries AGM batteries a bit more expensive and the more starter. Gel batteries are also different on purpose - there are both general-purpose and deep discharge. Traction - Designed for cycling. More suited for stand-alone power supply systems (such as onboard). But much more expensive starter and gel AB normally have a liquid electrolyte, maintenance-free and ventilated installation room. There are special "solar" - specially designed for the "hard" cycling. It is best to work with the flood pasted battery plates (series OPzS). These batteries are specially designed for use in stand-alone power systems.

10. Describe the lithium-polymer batteries.

Li-polymer battery (Li-pol or Li-polymer) this is an advanced design of lithium-ion battery. The electrolyte is a polymeric material with inclusions of gel-like, lithium-conductive filler. Used in mobile phones, digital devices, RC models, etc. Common household lithium polymer batteries are not able to give a large current, but there are special power lithium polymer batteries, capable to give the current 10 and 130 times greater than the numerical value of the capacity in ampere-hours. They are widely used as batteries for RC models as well as in portable power tools and in some modern electric vehicles.

Advantages: A large energy density per unit volume and mass (compared to lithium-ion); Low self-discharge; The thickness of the elements from 1 mm; The opportunity to obtain a very flexible shape; No memory effect; A slight voltage drop as the discharge. The operating temperature range of Li-polymer batteries are pretty wide: -20 to +40 deg. Celsius according to the manufacturers.

Disadvantages: Batteries are a fire hazard when overloaded and/or overheating. To combat this phenomenon all household batteries are supplied with a built-in electronic circuit that prevents overcharging and overheating due to a too heavy charge. For this reason, require special charging algorithms (chargers).

Number of cycles 800-900, when the discharge currents in 2S to loss of capacity in 20 % (compared to NiCd 1000 cycles, NiMH 500, LSD NiMH 1500, LiFePO4 — 2000). Generally speaking, any data on the number of cycles is still very little and to given in this case, their characteristics should be treated critically. In addition, their manufacturing technology is improving and it is possible that at the moment the figures for this type of battery is different.

Aging. Under the influence charge lithium polymer and lithium-ion batteries decrease capacity depending on temperature. Among the lithium batteries there are two main types - lithium-ion (Li-Ion) and lithium polymer (LiPo, Li-Po or Li-Pol). The difference between them is in the type of used electrolyte. In the case of LiIon is a gel electrolyte, in the case of a LiPo – polymer, lithium-containing rich solution. But for use in power installations the models most widely lithium polymer batteries, so in the future we will talk about them. However, the sharp division here is very conditional, as both types differ mainly in the used electrolyte, and all that is said about Li-polymer batteries, was almost fully applies to lithium-ion (charge, discharge, operating features, safety). From a practical point of view, we just care about the time that lithium-polymer batteries currently provide higher discharge currents. Therefore, to model the market as a source of energy for power plants mainly offer them.

Key features. Lithium polymer batteries have the same weight are superior in energy intensity 4-5 times NiCd, NiMH 3-4 times. Number of cycles of 500 - 600 with the discharge currents of 2C to loss of capacity in 20% (for comparison - NiCd - 1000 cycles, NiMH 500). Generally speaking, any data on the number of cycles is still very little and to given in this case, their characteristics should be treated critically. In addition, their manufacturing technology is improving and it is possible that at the moment the figures for this type of battery is different.