Series-first and parallel-second type power lithium battery pack

Abstract

The invention discloses a series-first and parallel-second type power lithium battery pack. According to the series-first and parallel-second type power lithium battery pack disclosed by the invention, single lithium cores are connected in series at first, and then, connected in parallel, so that standard battery modules are formed; the voltage and the capacity of the standard battery modules arecommon voltage and capacity of a second-cascade utilization product of a lithium battery preferentially; then, the standard battery modules are connected in parallel at first, and then, connected in series, so that the lithium battery pack is formed; in the standard battery modules, the single lithium cores are connected in series at first; therefore, the thermal runaway security risk of the battery pack due to short-circuiting of the lithium cores can be reduced; the working condition consistency of various series circuits can be realized along with increasing of the serial number; therefore,the cycle life of the battery pack is easily prolonged; then, parallel connection is carried out; the capacity loss of the battery pack due to deviation or fault of various series branches can be inhibited; and, due to preference selection of the voltage and the capacity of the cascade utilization product, the standard modules are disassembled to perform cascade utilization after the battery packis retired. The series-first and parallel-second type power lithium battery pack disclosed by the invention can be applied to the field of power battery technologies; and the commercial application prospect is wide.

Description

technical field [0001] The invention relates to the technical field of power lithium battery packs, in particular to an electrical connection method for cells in a power lithium battery pack. Background technique [0002] With the vigorous development of electric vehicles, power lithium battery packs have been widely used. At present, the common technical solution for the electrical connection of power lithium battery cells is to connect them in parallel first and then in series. The cells in the parallel branch can also share a BMS, which reduces the cost of the battery management system. [0003] However, the biggest problem with this electrical connection in parallel and then in series is the potential safety hazard. As we all know, the biggest safety hazard of lithium batteries is internal short circuit. For the connection in parallel and then in series, once one of the lithium batteries is short-circuited, the The other batteries connected in parallel to it will disch...

AI Technical Summary

Problems solved by technology

[0006] First of all, the internal short circuit risk of the battery still exists, because the occurrence of the internal short circuit of the battery has nothing to do with the external fuse of the battery. block the rest of the cells connected in parallel to the short-circuit cell for high-current discharge;

[0007] Secondly, due to the inconsistent internal resistance of the cells connected in parallel, the current flowing through each parallel cell is also inconsistent. Since the internal resistance of the lithium cell itself is very small, often a few mΩ to tens of mΩ, it is difficult to guarantee The internal resistance of each cell remains the same, and the current flowing through a cell with an internal resistance of 4mΩ is twice the current flowing through a cell with an internal resistance of 8mΩ! The fuse connected to the cell with smaller internal resistance and higher current has a higher risk of blown, especially when the battery pack is working at high power; at the same time, due to the internal resistance and current of each cell in the parallel circuit Inconsistency, the inconsistency of the working conditions of each battery cell will also lead to inconsistency in its aging and capacity attenuation, which in turn leads to aggravated battery pack capacity attenuation;

[0008] Secondly, in a circuit in which multiple batteries are connected in parallel, once the first battery fuses, the current borne by the battery will be shunted to the remaining batteries connected in parallel, which will intensify the phenomenon of the other batteries following the fusing. The result is that the capacity of the battery pack is attenuated!

[0009] In addition, the fuse is blown due to overheating, and the high temperature or even sparks generated during the blown process can easily ignite the leaked or volatilized electrolyte in the battery pack, thereby causing a safety accident in which the battery pack burns or explodes;

[0010] To sum up the above reasons, the current traditional technical scheme of electrical connection of lithium battery packs in parallel first and then in series not only has potential safety hazards caused by short circuit of the battery cells, but also has fast capacity decay and low cycle life of battery packs.

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