Compound cell balance system

Abstract

A compound cell balance system is connected with a battery pack protection system. The battery pack protection system comprises a master control core. The compound cell balance system comprises a plurality of passive balanced circuits, a plurality of battery chargers and a battery pack, wherein the battery pack is provided with a plurality of cells which are connected in series, and the battery pack is connected between the passive balanced circuits and a voltage and temperature monitoring module. The compound cell balance system is provided with a compound balance framework mainly used for combining active balance and passive balance, and thus the effective balanced current and the effective balanced capacitance needed by the large battery pack with the requirement for rapid charging can be provided.

Description

technical field [0001] The present invention relates to a battery cell composite balance system, in particular to a composite balance structure combining active balance (Active Balance) and passive balance (Bypassing Balance), which is used to provide the required battery pack for fast charging. The effective balance current and balance capacitance. Background technique [0002] General lithium, manganese, cobalt, nickel three-element batteries (Li-Mn-Co-NiO 2 ) In the process of charging and discharging, the cell voltage will vary greatly with the capacity (Variation), or in other words, the slight voltage difference caused by the characteristic difference between each cell will not affect the The common rule of judging the capacity of the battery cell by the cell voltage produces too much error, which is caused by figure 1 It can be seen from the figure that when lithium, manganese, cobalt, and nickel three-element batteries are charged and discharged at a rate of 0.5 (C...

AI Technical Summary

Problems solved by technology

[0010] 2. The rapid charging and discharging of the cells during the balancing process will cause errors in the reading of the cell voltage (the voltage is the result of electrochemical balance, and it will take time for the cells to display a stable voltage), resulting in an increase in the error rate of the balance decision , which further leads to the reduction of the "usable life" of the battery cell

[0011] 3. The efficiency of the active balancing circuit is not as high as imagined for the improvement of the battery with a lower voltage. If we look at a system with 12 strings and a maximum balancing current of 5 amps, the equivalent balancing current will be less than 250mA

[0012] 4. The active balancing circuit cannot solve the problem of voltage imbalance between battery modules under the requirement of low cost

[0021] 1. Since the charging bypass represents the consumption of electric energy, in addition to reducing the charging efficiency, it also generates heat. The temperature rise of the battery pack during charging is also an important consideration for the life of the battery pack. Therefore, the current limit of passive balancing is also relatively low. Active is more stringent

[0022] 2. Because it is a consumption balance, the balance current (Bypassing Current) will have to have a limit on the overall calorific value

[0023] 3. The difference in self-leakage of the battery cell must be limited, otherwise, for a battery pack that is used periodically, it will not be able to reach a balance in one or several charge and discharge cycles

However, because the characteristic curve of cell voltage versus capacity of lithium iron phosphate batteries is too flat, the rear balance type is not suitable for lithium iron phosphate battery packs.

[0024] 4. The overall charging efficiency is low

[0029] 3. No problem of energy transfer

[0031] 1. Since the wiring in the battery pack must be increased, the wiring will be complicated, which will reduce the safety of the battery pack

[0032] 2. The external contacts of semi-bare electric core wires may produce the acceptance effect of EMI / ESD impact and reduce the tolerance of the battery pack under EMC requirements

[0033] 3. The high cost of the high current and low voltage equalizing charging circuit poses a challenge to the cost of charging equipment. At the same time, the low conversion efficiency of the equalizing charging circuit itself is not conducive to the promotion of the high current equalizing charging and balancing system

[0034] 4. When used in large fixed or semi-solid battery systems, wiring will be the biggest problem in system assembly

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