Weak current College】 【high-voltage lithium-ion battery pack charging method】.

<br> <br> Abstract: this paper introduces the high-voltage lithium-ion battery pack of four charging method, and a comparison of the advantages and disadvantages. <br> Key words: high-voltage lithium-ion battery pack;; .tandem charge; parallel charging <br> <br> Abstract: Fourchargetechniquesofhighvoltagelithiumionbatterypackswereintroducedinthispaper, andtheiradvantagesanddrawbackswerecompared. <br> <br> Keywords: highvoltage; lithiumionbatterypack; seriescharging; parallelcharging <br> <br> Lithium-ion batteries because of work high voltage, small size ., light weight, no memory effect, pollution-free, low self discharge, cycle life long, and is an ideal source. In actual use, in order to obtain higher discharge voltage, generally at least two single lithium ion battery is a concatenation of .lithium-ion battery pack. Currently, lithium-ion battery pack has been widely used in laptops, electric bicycles and standby power supply, and many other areas. <br> <br> So how to charge the lithium-ion battery pack with good .particularly critical, the lithium-ion battery pack several charging method and I am of the view most suited to charging method on the following: <br> <br> 1 common-line charge <br> <br> Currently charging lithium-ion battery .pack is generally used in-line charge, this is mainly because tandem charge method of simple structure, low cost, easier to implement. But as the single lithium ion battery in capacity, internal resistance, attenuation, self-discharge, performance differences, lithium .-ion battery pack is charging, the battery in series in the capacity of the smallest of the monomer lithium-ion battery is fully charged will be the first one, but at this point, no other battery fully charged, the charge, if you continue .the series has been fully charged lithium-ion battery as monomers may be overcharge. <br> <br> And the lithium ion battery overcharge will seriously damage the battery's performance and may even lead to explosions causing personnel's injury, therefore, in order to prevent .a single lithium ion battery overcharge, lithium-ion batteries used in General with a battery management system (BMS BatteryManagementSystem, abbreviation), battery management system on every single lithium ion battery for overcharge protection. In-line charge, if you have a single lithium .ion battery voltage reaches the overcharge protection voltage, battery management system will cut off the entire series charging circuit, stop charging, to prevent the single cells being overcharge and this will cause other lithium-ion battery is not charged. <br> <br> .After years of development, lithium iron phosphate batteries because of the higher security, very good, circular performance advantage has been basically meet the electric vehicle in particular requirements of electric car, the basic process is also equipped with mass production conditions. However, lithium iron .phosphate battery performance and other lithium-ion battery with a difference, especially its voltage characteristics and manganese lithium battery, lithium battery, cobalt. The following is the lithium iron phosphate and two lithium manganese lithium-ion battery charging curve and lithium-ion removal of .ingrown correspondence: <br> <br> <br> <br> <br> <br> From the top of the curve is not difficult to see, lithium iron phosphate batteries fully charged in fast, lithium-ion almost entirely from the cathode .to the anode, with embedded battery terminal voltage will increase rapidly, charging curve upwards, this can cause the battery can easily reach the overcharge protection voltage. Therefore lithium iron phosphate battery charging and the battery pack in some discontent with the electrical phenomena relative terms of .manganese lithium battery will become more apparent. <br> <br> In addition, although some battery management system with balanced function, but because of the cost, thermal, reliability in many aspects to consider, battery management system for a balanced current generally far .less than the current series charging, thus balancing effect is not very obvious, but also some single battery charge and dissatisfaction with electricity, which need high current charging lithium-ion batteries, such as electric vehicles used for the purposes of lithium-ion battery pack .is more obvious. <br> <br> For example, will discharge capacity is only 100 to 100Ah of lithium-ion batteries in series to form the battery pack, but if a group of former 99 only single charging lithium-ion battery 80Ah, .1 only single charging lithium-ion battery, batteries 100Ah for in-charge, which charged that the monomer 100Ah lithium-ion battery will be fully charged, so as to achieve the overcharge protection voltage, in order to prevent this monomer were lithium-ion .battery overcharge, battery management system the entire inline cutting, charging circuit also makes other 99 only battery cannot be charged to the entire battery discharge capacity is only 80Ah. <br> <br> General battery manufacturers factory testing capacity is the single battery first constant .current charging then constant voltage charging, and constant-current discharge and thus measured discharge capacity. General discharge capacity approximately constant current charging capacity combined with a constant voltage charging capacity. The actual battery-charging process on single cells, generally do not have constant pressure .charging process, the constant pressure charging capacity will not, battery capacity will be less than the single battery capacity. But in General, the smaller the charging current, constant voltage charging capacity ratio is smaller, the smaller capacity battery pack loss, therefore also developed .battery management system and charger coordination-charging mode. <br> <br> 2 battery management system and coordination between series charger charging <br> <br> Battery management system is on the battery's performance and status of the understanding of the most comprehensive equipment ., battery management system and establish links between the charger, the battery charger real-time information about the battery to more effectively address the battery charging is producing some of the issues, the schematic below. <br> <br> <br> <br .> <br> <br> <br> <br> Battery management system and charger coordination principles to charge mode: battery management system through a battery of current status (such as temperature, single battery voltage, battery operating current, consistency and temperature, .etc.) for monitoring and use of these parameters on the current cell's maximum allowable charge current estimates; charging process, through communication cable battery management system and battery charger, for data sharing. Battery management system will total voltage, maximum single battery voltage, maximum .temperature, temperature, maximum charge voltage, maximum allowed single battery voltage and maximum charging current parameters in real time to the charger, charger can under battery management system provides information to change its own charging policy and output current. <br> <br> When .the battery management system provides maximum charging current design than the charger's current capacity is high, charger, in accordance with the design of the maximum output current of the charge; when the battery voltage, temperature gauge, battery management system immediately detected and promptly notify the .charger change current output; when the charging current is greater than the maximum allowable charge current, the charger starts to follow the maximum allowable charge current, thus effectively prevent the battery overcharge, reach the purpose of extending battery life. Charging process in the event of .a failure, battery management system you can set the maximum allowable charge current is set to 0, forcing the charger downtime, prevent accidents and protect the safety of the charge. <br> <br> In the charge, both improved battery management system of .management and control functions, while the charger based on battery status, change the output current in real time, to prevent the occurrence of all batteries in the battery overcharge and optimal charging purposes, actual discharge capacity of the battery must also be greater than the normal .series charging method, but it still cannot solve the battery pack in the battery charging and dissatisfaction with the power of questions, especially when the battery pack with a few more, battery charging current consistency, is large. <br> <br> 3 parallel .charging <br> <br> In order to solve the battery pack in some single battery charge and unfulfilled electrical problem developed parallel charging methods, the schematic below. <br> <br> <br> <br> But parallel charging method requires multiple .low voltage, high current charging power for every single battery charge, charging power supply costs, reliability, low power, low efficiency, connected defects such as coarse wire diameter, so there is no widespread use this charging method. <br> <br> .4-line high current charging and recharging small current shunt <br> <br> As a result of the above three charging method poses a problem, I developed a most suitable for high-voltage battery, especially electric vehicle battery charging method, which uses .the battery management system and charger coordination series high current charging plus · drive parallel pattern of small charging current, schematic diagram see below. <br> <br> <br> This charging method has the following characteristics: <br> <br> ( .1) due to this system of BMS has the function of preventing overcharge, thereby ensuring that the battery will not appear the overcharge. Of course if BMS cannot communicate with the parallel charging power supply and control, due to parallel charging power supply voltage value in .General and in the lithium-ion battery pack single lithium ion battery is fully charged when the voltage values are the same, so it doesn't suffer the overcharge. <br> <br> (2) due to parallel the charge there is no .need for a low reliability, cost relatively high balance circuit, and the charging effects are better than only balance circuit series charging method, and its maintenance management is easy. <br> <br> (3) since the series charging maximum current is much .larger than parallel charging current (usually 5 times more), so you can guarantee that in a relatively short period of time filling in a high-capacity, thus the maximum-line charge. <br> <br> (4) while charging, .charging and parallel charging series as well as the number of parallel charging power supply can be flexibly, can simultaneously charge; you can end the series charging after parallel charge; you can also use a parallel charging power supply according to battery pack voltage in the battery .to the minimum voltage for charging in rotation. <br> <br> (5) as the technology development, parallel charging power supply can provide non-contact charger (Wireless charging power supply) or solar power, enabling parallel charging. <br> .<br> (6) when the lithium-ion battery pack in the number of single lithium ion battery more, you can set the lithium-ion battery pack is divided into several modules for lithium-ion battery pack, each lithium-ion battery pack .module using BMS and charger coordination series high current charging and · drive parallel combining small charging current of the charge. <br> <br> Its primary purpose is to reduce the number of series battery in the battery more, single cells relatively worse between consistency ., causing the BMS and charger coordination of charging method of charging effects differential weakness to play out of BMS and charger coordination maximum charging mode. <br> <br> This method is especially suitable for high voltage battery pack is a quick replacement of low voltage .(for example 48V) battery module system consists of battery system, so that you can charge the battery replacement station or stations parallel charging or repair (normal users usually charge can do parallel charge), and by hand according to the actual situation for sorting and .distribution groups. <br> <br> In short, the use of battery management system and charger coordination series high current charging plus · drive parallel small current charge charging method can be an effective solution to rechargeable lithium-ion battery pack-line overcharge occurred ., unfulfilled power problem, and to avoid parallel charging rechargeable power cost, reliability, low power, low efficiency, connection diameter thick, is by far the most suitable for high-voltage battery, especially electric vehicle battery charging methods. <br>.