CN215418298U - Modularization lithium iron phosphate battery pack with partial charging protection circuit - Google Patents

Abstract

The utility model discloses a modular lithium iron phosphate battery pack with a partial charging protection circuit, and belongs to the technical field of lithium batteries. The lithium iron phosphate battery pack comprises a plurality of battery modules which are independent in mechanical structure and are arranged in series, wherein each battery module comprises a plurality of standard battery modules and a protection battery module, and the protection battery module is positioned at the total negative pole position of the lithium iron phosphate battery pack; the standard battery module and the protection battery module respectively comprise a plurality of batteries connected in series; two ends of each battery are connected with two-end voltage-stabilizing tube type equalizing circuits in parallel; and two ends of all or part of the batteries in the battery protection module are also connected with a charging protection circuit in parallel. Compared with a standard battery module, the protection battery module is always in a charge leading position, so that the charging protection is provided in the charging process of the battery pack, and the safety is high; meanwhile, a discharge protection circuit is not required to be arranged in the battery pack, and actual discharge protection depends on an external circuit or an undervoltage protection device provided by an electric appliance.

Description

Modularization lithium iron phosphate battery pack with partial charging protection circuit

Technical Field

The utility model belongs to the technical field of lithium batteries, and particularly relates to a modular lithium iron phosphate battery pack with a partial charging protection circuit.

Background

The lithium ion battery pack is formed by connecting a plurality of lithium ion batteries in series, and the charging process of the lithium ion battery pack can be generally divided into two stages. The first stage is a direct charge stage, where all cells in the same string get the same charge until a voltage leading the cell first reaches full charge voltage. And then, entering a second stage, namely an equalizing charge stage, wherein equalizing lines arranged at two ends of the battery which reaches the full-charge voltage are started to be conducted, bypassing a part of charging current which is bypassed, namely the equalizing current, starting equalization until the battery with the lagging voltage is fully charged one by one, and ending charging. In the process, as the charging current is generally larger than the equalizing current, the voltage of the fully charged battery can continuously rise, and then the charging protection is triggered to disconnect the charging circuit. At this time, due to the continuous work of the equalizing circuit or the self-discharge effect of the batteries, the voltage of the batteries gradually decreases to reach the value of removing the protection, the charging channel is restarted, the voltage of the batteries starts to rise again, and the operation is repeated in a circulating mode until all the batteries are fully charged. The equalizing charge time depends on the maximum charge difference and equalizing current of each battery in the battery pack. This difference in charge is generally equal to the product of the difference in self-discharge current of the leading and trailing batteries and the time between charges. In general, the voltage leading battery is not a specific battery, and therefore, the voltage of each battery of the battery pack needs to be effectively detected. Similarly, for discharge protection, the voltage of all the cells also needs to be detected. When the battery voltage exceeds the set charge-discharge protection limit, the battery management system (hereinafter referred to as BMS) may shut down the electrical connection between the battery pack and the external lines, terminating the occurrence of unsafe or unreliable conditions that may occur, and higher-level BMS may also integrate communication and other functions.

Because a complete BMS circuit needs to monitor the voltage of each battery in the battery pack, the required detection cables are connected to the two ends of each battery to be detected, then the cables are finally gathered to a circuit board with a master control function, because the wire harnesses are many and the wire diameter is thin, the test wire harnesses can not be used as external leads to be bridged between different battery modules, the lithium ion battery packs with the complete BMS circuit are all integrally designed, the integrally designed lithium ion battery packs are often large in size and difficult in structure change, and the application range of the lithium ion battery packs is greatly limited.

The general lithium ion battery charging and discharging management system comprises a switch type equalizing line design, when the voltage of a battery reaches a specific value (3.65V), the equalizing line starts to be conducted, and the equalizing line is restarted when the voltage drops to the specific value. Such a switching device is generally a field effect device, which is a lot of field effect devices, and is greatly affected by the assembly environment, and the reliability is slightly poor. But any such open circuit failure of the equalization lines will not cause the battery pack to fail due to the presence of the complete BMS lines. The consumer will not be readily aware of it. The lack of functionality of some switched equalization lines can gradually detract from the uniformity of the battery pack, resulting in a relatively rapid decay in the available capacity of the battery pack due to the gradual expansion of the difference between the leading and trailing battery charge of the battery pack, rather than the degradation of individual cells. Meanwhile, the equalizing line of the BMS with the general design is difficult to radiate due to limited space, so that the power of the equalizing line is greatly limited, and the equalizing line is particularly suitable for the lithium iron battery pack. Therefore, in the prior art, the lithium iron phosphate battery mainly has the following technical problems: the existing BMS wiring is usually a complete wiring and is generally of an integrated design, so that the battery pack tends to be bulky and difficult to change in structure, limiting its range of application, particularly in terms of equivalent replacement of lead-acid power batteries. Meanwhile, the switch type equalizing line has small power and poor reliability, the failure of the switch type equalizing line can cause the rapid attenuation of the available usage amount of the battery pack so as to reduce the whole service life of the battery pack, and further, the switch type equalizing line must rely on the full protection provided by a complete charging and discharging protection line.

SUMMERY OF THE UTILITY MODEL

Self-discharge is a key indicator of the charge retention capability of a battery, which is an insurmountable drawback. Generally, lithium iron batteries are considered to have poor consistency in the industry, and mainly refer to that the lithium iron batteries have larger self-discharge current and poor charge retention capacity compared with other lithium ion batteries. The charge difference of each battery in the lithium iron phosphate battery pack to be charged needs to be compensated in a differentiation mode through the work of the balancing circuit, and therefore a more efficient balancing circuit design is needed. In the same battery pack, since the self-discharge rates of the batteries are not consistent, after a period of time of accumulation, the state of charge of each battery, namely the consistency of the battery pack, is greatly influenced, a leading battery becomes a small self-discharge, and a lagging battery becomes a large self-discharge. The utility model discloses a design of a lithium iron phosphate battery charging leading circuit, which introduces a circuit, wherein the circuit has considerable equalizing current at the full-charge voltage of the lithium iron phosphate battery, and the working current at the voltage platform of the lithium iron phosphate battery can be properly adjusted, so that one or more charging leading batteries are designed, and a charging protection circuit is arranged on the charging leading batteries.

The utility model aims to replace a general switch type equalizing circuit with a two-end voltage-regulator tube type equalizing circuit for a lithium iron phosphate battery pack disclosed in the prior patent application (201710601910.9) of the applicant, and the two-end voltage-regulator tube type equalizing circuit is designed by selecting a high-power semiconductor device and a PCB heat-conducting base material, so that the design is simple and has high power. The existence of the high-power continuous equalizing line avoids the use of a complete charging and discharging protection line under specific conditions, so that the designed lithium iron phosphate battery pack can be conveniently decomposed into a plurality of module batteries, and meanwhile, the capacity attenuation of the battery pack is slower, thereby solving several technical problems mentioned in the background technology.

As in the case of the prior patent application, the two-terminal zener diode equalizer circuit preferably has two and only two power diodes connected in series, at least one of which is a light emitting diode LED. The current (hereinafter referred to as working current, which can be adjusted) of the lithium iron phosphate battery at the platform voltage of the lithium iron phosphate battery is far less than the equilibrium current of the lithium iron phosphate battery at the full-electricity voltage, but far greater than the self-discharge current of the battery. Therefore, when a voltage regulator tube with a small working current is connected to the two ends of one battery, the battery becomes a leading battery in the battery pack. The two-end voltage-stabilizing tube type equalizing circuit has the advantages of low cost, simple design, high power, high voltage resistance, high reliability and the like.

In order to achieve the above object, the present invention discloses a modular lithium iron phosphate battery pack with a partial charging protection circuit, comprising a plurality of mechanically independent battery modules arranged in series, wherein each battery module comprises a plurality of standard battery modules and a protection battery module, and the protection battery module is located at the total negative electrode position of the lithium iron phosphate battery pack; the standard battery module and the protection battery module are respectively provided with a plurality of batteries connected in series, and two ends of each battery are connected in parallel with a two-end voltage-stabilizing tube type equalizing circuit which has the function of self-discharge control; and two ends of part or all of the batteries in the battery protection module are also connected with a charging protection circuit in parallel, and the batteries connected with the charging protection circuit in parallel are protection batteries.

Further, the total cell string number of the lithium iron phosphate battery is m, the string number of the protection cell is n, and the number is less than or equal to 1 and less than or equal to 25 percent and less than or equal to m.

Further, the capacity deviation of all cells is ≦ 5%.

Further, the working current of the two-end voltage-stabilizing tube type equalizing line connected in parallel at the two ends of the protection battery is lower than the working current of the two-end voltage-stabilizing tube type equalizing line connected in parallel at the two ends of other batteries in the lithium iron phosphate battery pack.

Furthermore, the working current of the two-end voltage-stabilizing tube type equalizing line connected in parallel at the two ends of the protection battery is 5% -20% lower than that of the two-end voltage-stabilizing tube type equalizing line connected in parallel at the two ends of other batteries in the lithium iron phosphate battery pack.

Furthermore, the two-terminal voltage regulator tube type equalizing circuit comprises a voltage regulator diode.

Further, the two-terminal stabilivolt type equalizing circuit comprises two diodes connected in series in a forward direction, wherein at least one diode is a Light Emitting Diode (LED) device.

Further, no discharge protection circuit is arranged in the modular lithium iron phosphate battery pack.

Compared with the existing integrated battery pack products, the lead-acid battery pack modular design is referred to, and the lead-acid battery pack modular design is targeted to be used as an alternative for the existing after-market lead-acid power batteries. The battery pack is composed of a plurality of battery modules, wherein one battery module is a charging protection battery which is always in a charge leading position compared with other standard batteries in the same group, and the charging protection is provided in the charging process of the battery pack. And the lithium iron phosphate battery pack is decomposed into several independent battery modules. The plastic shell of the lead-acid battery is used as the shell of the battery module, so that the lead-acid battery has great installation convenience in the after-sale market of the lead-acid battery, and meanwhile, the discharge voltage of the lead-acid battery is set according to the lead-acid battery with the same specification, so that any internal circuit of an electric appliance does not need to be changed.

Drawings

FIG. 1: discharge performance test curve of 12V module battery.

FIG. 2: the utility model discloses a circuit diagram of a modular lithium iron phosphate battery pack with partial charging protection circuits.

FIG. 3: the utility model discloses a circuit diagram of a two-end voltage-stabilizing tube type equalizing circuit.

FIG. 4: a circuit diagram of a preferred modular lithium iron phosphate battery pack of the present invention.

FIG. 5: the utility model relates to a charging performance test curve of each battery module in a modular lithium iron phosphate battery pack.

Description of reference numerals: 1-standard battery module; 2-protecting the battery module; 11-a first standard battery module; 12-a second standard battery module; 13-a third standard battery module; 21-charging protection circuit.

Detailed Description

The technical solution of the present invention will be described in detail by the following specific examples.

The lead-acid battery is invented more than 160 years ago, and is economical and durable due to high safety. Lead-acid batteries are used as power batteries, starting batteries, UPS (uninterrupted Power supply) batteries, energy storage batteries and the like, and are still widely used in various living and working places. A lead-acid battery pack is generally composed of a plurality of battery modules, and the positive and negative electrodes of the battery modules are connected one by one to form the battery pack. The lead-acid battery pack does not need to be provided with a protection circuit like a BMS (battery management system) configured by a lithium ion battery, and the basic protection of the lead-acid battery pack is formed by charging protection provided by a charger and undervoltage protection provided by an electric appliance. Compared with a lithium battery with a complete BMS integrated appearance, the lead-acid battery has the advantages that the lead-acid battery has the modularization characteristic and is very convenient to assemble and install. Lithium ion batteries have overwhelming advantages over lead acid power batteries, including service life and energy density. With the continuous popularization of electric automobiles and the maturity of power lithium ion battery technology in these years, the unit cost of the electric automobiles is gradually lowered, and the economic replacement of lead-acid batteries is possible. However, the current popular integrated lithium ion battery products are in the wide after-market of lead-acid power batteries, and a great obstacle is created due to the limitation of product forms, which is the problem to be solved by the patent application.

A single lithium iron phosphate battery has an extremely long cycle life, but due to the problem of a system integration method, the power of a general switch type equalizing line is small and the reliability is poor, so that the service life of a commonly designed lithium iron phosphate battery pack often cannot meet the expectation of consumers, the long cycle life in the expectation is difficult to realize, and the development of the market is hindered.

In the utility model patent application (201710601910.9), a composite voltage stabilizing circuit for a lithium iron phosphate battery pack, a two-terminal voltage stabilizing tube type equalizing circuit is disclosed as an equalizing circuit of the lithium iron phosphate battery pack. The method provided by the patent application aims at solving the problem, and a high-power voltage-stabilizing pipeline (the balance current is required to reach 1-10% of the battery capacity) is used for permanent connection. And meanwhile, the working current and the difference of the working current at the platform voltage (3.300V) of the lithium iron battery are strictly inhibited, excessive electric leakage when the battery pack is idle for a long time is avoided, and meanwhile, the charge state (or the balance state) of the battery pack is seriously and adversely affected. The current regulation requirement at 3.300V is 5%, which is equivalent to the voltage deviation of the precision voltage stabilizing diode in constant temperature and constant current test is less than 3 millivolts.

In the utility model patent application, the precise composite two-end voltage-stabilizing tube type equalizing line is formed by connecting two diode elements in series, wherein at least one of the two diode elements is an LED, the LED has precise and consistent current-voltage characteristics at the voltage of 3.3V of a battery platform of a lithium iron battery, and simultaneously has excellent voltage-stabilizing characteristics in the whole working voltage range of 2.5-4.0V. The two-end line is permanently connected to two ends of each battery in the lithium iron battery pack, strictly consistent working current is provided at the position of 3.300V of a platform of the lithium iron battery, considerable balance current (balance current for short in the following) is provided at the position of 4.0V of full-electricity voltage, and the working current of the balance line at the position of 3.3V is far larger than the self-discharge current of a battery core. Because the charge-discharge efficiency of the lithium ion battery is close to 100%, the charge leading position of each battery cannot be influenced by the general deep discharge. The working current of the two-terminal voltage-stabilizing pipeline is also a part of the total self-discharge of the battery, and when the total self-discharge of each battery in the same battery pack is different, the charge state of each battery in the battery pack can be obviously changed after a certain time of accumulation. When the voltage-stabilizing line circuit with small working current is connected to several specific batteries, because of small total self-discharge, these batteries become charge-leading batteries, which reach full-charge voltage earlier when charging, and the charge protection circuit is arranged on these charge-leading batteries, which can protect all batteries from overvoltage. Meanwhile, the high-power voltage stabilizing tube equalizing circuit can quickly reduce the charge difference of each battery, and the voltage of each battery is quickly leveled to be uniform and consistent full-electricity voltage.

The battery pack product only provided with the two-end voltage stabilizing tube type equalizing circuit without any built-in protection circuit is also applicable to specific applications, and particularly the highest voltage output by the charger is strictly limited. However, in practical open application scenarios, such as battery overvoltage damage caused by misusing a charger, excessive electric leakage caused by long-time high-temperature shelf storage, serious imbalance of uniformity inside the battery pack, and the like, there is a sharp rise in the probability of battery pack charging and discharging failure. Therefore, on the premise of ensuring the shape of the existing battery product, a certain charging protection design needs to be introduced, and meanwhile, necessary warning is provided for discharging use under specific conditions.

It should be noted that the general concept in the industry is that lithium batteries are unsafe, and BMS is required to manage the safety risks under various abuse conditions while ensuring full performance of the battery. This is because the safety characteristics of various lithium batteries cannot be well measured and compared. The safety of the lithium iron battery is far better than that of a ternary battery or a lithium cobaltate battery. Referring to the probability of spontaneous combustion of electric vehicles with different types of lithium batteries in news reports, the lithium iron battery has extremely high safety as proposed by various books. The safety protection requirements for lithium iron batteries are not necessarily as stringent as for polymer lithium batteries. Based on the above technical solutions, the applicant believes that it is a completely feasible solution to manufacture a long-life lithium iron battery pack without a complete BMS circuit, by making use of the high safety of lithium iron batteries, suitably enhanced in terms of product mechanics.

There are two sets of semiconductor switching devices on the main circuit of the BMS circuit for controlling the charging current and the discharging current, respectively. These switching devices are all field effect MOS devices under general application conditions, and since the current channel capability of a single-packaged MOS device is limited, it is often necessary to connect a plurality of MOS devices in parallel to obtain a larger control capability in order to obtain a larger current. In power battery application, no matter lead-acid or lithium ion power batteries, generally, the charging current is much smaller than the allowed discharging current, so that the number of MOS tubes for controlling discharging is large.

In the practical application of the power battery pack for driving the vehicle, the motor is charged by a corresponding charger and discharged. When the protection is triggered respectively, the corresponding MOS tube needs to be turned off. The voltage difference dropped across the charging MOS switch is typically no greater than 12V, while the voltage difference dropped across the discharging MOS switch is the voltage of the battery pack, or slightly higher. Meanwhile, for one power battery, the lower the total internal resistance is, the better the output characteristic is, and the higher the driving efficiency is. A MOS transistor as discharge control contributes to a part thereof. The conduction internal resistance of one MOS tube is close to the direct proportional relation with the withstand voltage thereof. Therefore, the MOS transistor for discharge control needs a larger current and a higher withstand voltage than the MOS transistor for charge control, and the MOS transistor for discharge control also needs to have a minimum on-resistance, and thus, the high cost is required to solve the contradiction, and the reliability thereof is also problematic. In contrast, the MOS transistor for charge control requires low current and voltage resistance requirements, and thus has low associated costs and higher design reliability.

The lithium iron phosphate battery has a flat charging and discharging voltage curve, most energy is concentrated near the platform voltage, the charging is slightly higher, and the discharging is slightly lower. During the discharge process, about 90% of its charge will be discharged at the voltage plateau, whereas its last 10% of its charge, its discharge voltage will drop rapidly with the discharge of the residual capacity. When the charge consistency states of the batteries are good and the capacity difference is less than 5%, the final discharge voltage difference of each battery is very small, and meanwhile, the lithium iron battery has good tolerance to discharge undervoltage, so that the excessive discharge of a single battery can be prevented only by monitoring the total voltage of the battery pack and carrying out proper undervoltage protection.

The undervoltage protection device is in a standardized configuration on two or three-wheeled electric vehicles with the original lead-acid batteries, so that in the specific applications, the lithium iron battery pack disclosed by the utility model is used for replacing the lead-acid batteries with corresponding specifications without replacing any vehicle circuit, particularly a controller. The necessary premise to be mentioned is that the capacity difference of each battery in the battery pack is small, and the battery pack is always in a good balanced state, and a high-power stable and reliable balanced line is required for obtaining the good balanced state, which is also the characteristic of the high-power voltage regulator tube balanced line.

A 20AH module battery with a nominal voltage of 12V (actually 12.8V) and formed by connecting four lithium iron phosphate batteries in series is extracted for a discharge test, a 0.5C (10A) discharge test curve is shown in fig. 1, a generally set discharge cut-off voltage is 10.5V, the discharge cut-off voltage is consistent with that of a 12V lead-acid battery, and the actual discharge depth of the lithium iron phosphate batteries can be actually deeper (-2V single string). And detecting the voltage change condition of the module battery. During the final release of-10% of the electricity, the battery voltage drops sharply, triggering the discharge protection. When the capacity deviation of a plurality of batteries in the same battery is small, the drops are relatively synchronous, and the lowest discharge voltage of each battery module is concentrated on about 10.5V, so that a certain safety design margin is kept above an absolute lower limit (8V).

Therefore, the battery capacity difference is effectively controlled by utilizing the near-linear characteristic of the tail end of the discharge curve of the lithium iron battery, the battery pack is ensured to be in a good balanced state at any time by utilizing the high-power voltage-stabilizing tube balanced circuit, meanwhile, the proper under-voltage protection device is arranged on the outer circuit, the BMS discharge management circuit can be avoided by the design, the cost is saved, the power and the reliability are improved, and the feasibility of the design of the modularized battery is ensured by the design.

When the lithium iron phosphate battery pack is in a charging state, once the voltage of a single battery cell exceeds 3.50V, the capacity increase obtained by continuous charging is very little, however, until 4.0V, the lithium iron battery cannot be damaged by overvoltage in a short time, so that the upper limit management of the charging voltage of the lithium iron battery is very flexible, the 4.0V is called as the limit withstand voltage of the lithium iron phosphate battery, and under the voltage, the current of the equalizing line of the set voltage stabilizing diode is the maximum equalizing current. The lowest full-electricity voltage of the lithium iron module battery constructed by the precise voltage-stabilizing diode continuous equalization circuit based on the patent application is 3.50V, and the voltage-stabilizing tube equalization circuit configured on the battery pack is permanently communicated and always in an effective equalization working state, so that the voltage setting required by the charger has great flexibility, namely, the voltage is from 3.50V to 4.00V. Therefore, the newly designed lithium iron phosphate battery pack can set lower total charging voltage, and the overcharge risk of the battery pack is reduced to the maximum extent.

The starting voltage of a charging protection circuit of a common lithium iron phosphate battery is set between 3.65 and 3.75V, when the voltage of any detected battery reaches a set protection point, a charging circuit is turned off until the voltage of the battery drops (through a self-discharging or equalizing circuit) to a set voltage value for removing protection, and a charging channel is opened to restore charging. In this way, due to the existence of the high-power continuous equalization line, the voltage of each battery can be gradually leveled to reach a consistent equalization state.

The lithium iron battery has high charge-discharge charge circulation efficiency which is very close to 100% as with other lithium batteries, and after the leakage current of the battery is effectively controlled and regulated, and the working current of a voltage stabilizing tube equalizing circuit connected with the battery is adjusted, a small number of leading batteries can be designed, and the batteries can be in a leading state during charging, and the voltages of the batteries are detected, but not the voltages of all the batteries in the battery pack, so that all the batteries can be effectively protected. The voltage-regulator tube type continuous equalizing circuit can greatly reduce the charging voltage by providing larger equalizing current, and the charging voltage is generally set to be 3.55V multiplied by the number of battery strings, which is 0.10V lower than the charging voltage of a common lithium iron battery pack. It should be noted that the wrong use of the charger with higher voltage (12V) in the same specification will not cause instant failure to the battery pack, and the safety of the lithium iron battery is high, so that the newly designed lithium iron battery pack has good applicability to various chargers, or has higher abuse resistance.

Since the state of charge of a protective battery is slightly higher than that of an unprotected battery, in extreme cases, such as deep discharge after long-term idle storage, a standard battery with less charge will reach a depleted state before the protective battery. These standard cells will discharge more deeply with the overall discharge protection voltage limit unchanged. In order to avoid the damage caused thereby, it is necessary to define the number of strings protecting the battery, and when this ratio is lower than 25% based on the ratio of the total number of strings of the battery pack, the risk of the overdischarge damage of the battery in such an abnormal state can be effectively managed. Even if the damage finally happens, a few batteries are damaged, in the next charging link, due to the existence of a protection circuit, under the condition that other batteries can still be effectively fully charged, the total voltage of the batteries can drop greatly in the use process, the vehicle can still ride at the moment, but a user can timely find out the problem and report the problem, and the use of the user can be prevented from being influenced by the further damage of the batteries.

Four strings of lithium iron battery modules are generally used to replace a 12V lead-acid battery, and the following tests are also arranged in such a way, but the discharge platform voltage of the four strings of lithium iron is 12.8V. Therefore, in a battery pack with a higher voltage, the total string number of the batteries can be reduced properly, for example, nineteen lithium iron battery packs are used instead of twenty battery packs to replace 60V lead-acid battery packs, so that the discharge protection of the battery pack is more sufficient, the cut-off voltage of a single string of batteries can be increased from 2.63V to 2.76V by setting a 52.5V limit value for 60V lead-acid, and the problems of power shortage and inconsistent voltage of each battery module are brought.

In addition to the self-discharge of the battery itself requiring timely operation of the balancing circuitry, any circuitry connected to the two ends of a single battery will have independent operating currents if its operation relies on the power supplied by the single battery rather than the entire battery pack. These operating current values are not exactly the same, and the difference in the operating current values also has the same effect as the self-discharge of the battery, resulting in a gradual imbalance of the battery pack over time.

The equalization lines, which are usually controlled by the BMS, are switched off during non-charging times or near the plateau voltage of the batteries, while the battery management system requires operating current from the entire battery pack, so that the power of the individual batteries is completely identical over time, and the power that is lost in a consistent manner can be replenished without the intervention of the equalization lines during the direct charging phase.

As shown in fig. 2, a circuit diagram of a modular lithium iron phosphate battery pack provided with a partial charging protection circuit according to the present invention includes an n-string lithium iron phosphate battery group b1.. Bx... By, Bz... Bn, which includes a plurality of standard battery modules 1 and a protection battery module 2, where the protection battery module 2 is located at a total negative electrode position of the lithium iron phosphate battery pack, and a plurality of batteries connected in series are respectively disposed in each of the standard battery modules 1 and the protection battery module 2; in the protection battery module 2, the charging protection circuit 21 is connected in parallel to both ends of the remaining batteries except the first battery, and in the protection battery module 2, the battery connected in parallel to the charging protection circuit 21 is a protection battery. Meanwhile, in the standard battery module 1 and the protection battery module 2, a two-terminal regulator tube type equalizing line d1.. Dx... Dy, Dz... Dn is connected in parallel at both ends of each battery, and in the two-terminal regulator tube type equalizing line, there are three circuit design methods, as shown in fig. 3: (1)3 a: a single zener diode; (2)3 b: two diodes connected in series in the forward direction, one of which is a Light Emitting Diode (LED) device; (3)3 c: two diodes in series in the forward direction, both light emitting diode, LED, devices.

Compared with two-end voltage-stabilizing tubular equalizing lines Dz... Dn, which are connected in parallel at two ends of the protection battery, and two-end voltage-stabilizing tubular equalizing lines D1.... Dx and Dy, which are connected in parallel at two ends of other batteries, specific parameters are different, specifically: the operating current of the two-terminal regulator tube equalizing line Dz... Dn is about 5% -20% lower than that of the two-terminal regulator tube equalizing line d1...... Dx and Dy, so that the corresponding battery Bz... ann.bn (i.e., the protection battery) in the protection battery module 2 is always in a charge leading position.

A charging protection circuit 21 is arranged on the battery in the protection battery module 2, specifically, the charging protection circuit 21 is arranged on other batteries except the first battery in the protection battery module 2; in other embodiments, the charge protection line 21 may be provided on all the batteries in the protection battery module 2.

The charging protection circuit 21 may adopt any charging protection circuit for an iron-lithium battery in the current market, for example, refer to the charging protection circuit design in chinese patent application 201910063687.6 (a lithium battery pack safety charging protection method and charging protection circuit thereof), the charging protection circuit 21 may monitor the voltage of the corresponding battery, and turn off the charging channel P-when necessary, where B + and B-are the total positive electrode and the total negative electrode of the discharging channel, and P-is the charging protection negative electrode channel, and this design is also called as an exclusive design, that is, the charging and discharging negative electrodes are disposed at different ports. When a diode or an MOS tube is connected between the P-and the B-to allow the current to pass in a single direction when the battery discharges, the battery pack is designed to be of the same port design, namely, the charge and discharge cathode ports are P-while the B-port is in an idle state.

When the battery pack is in the above different port design, the discharge channel is not provided with any semiconductor switching device, which provides a ready charging channel for the electric vehicle with energy recovery without passing through the original charging dedicated cathode P-.

In this embodiment, the entire battery pack is divided into several battery modules, respectively a plurality of standard battery modules 1 and a protective battery module 2. The plastic housing of the standard setting of the existing lead-acid battery can be utilized as the housing of the module batteries in general, and the plastic housing has excellent installation convenience when being used for replacing the lead-acid battery in a practical application scene.

As shown in fig. 3, in this embodiment, the battery module includes three standard battery modules and a protection battery module 2, the three standard battery modules are sequentially marked as a first standard battery module 11, a second standard battery module 12, and a third standard battery module 13, each standard battery module is respectively provided with four batteries in series, which are respectively B1-B4, B5-B8, and B9-B12, and in the protection battery module 2, four batteries are also provided in series, which are respectively B13-B16; but only on three batteries B14-B16.

In the standard battery module 1, two ends of each battery B1-B12 are connected in parallel with two-end voltage-regulator tube type equalizing circuits D1-D12; in the protection battery module 2, two ends of each battery B13-B16 are connected in parallel with two-end voltage-regulator tube type equalizing circuits D13-D16; in the protection battery module 2, the charging protection circuit 21 is respectively connected in parallel at two ends of the batteries B14-B16, that is, in the protection battery module 2, the charging protection circuit 21 is connected in parallel at two ends of a part of the batteries, in the charging protection circuit 21, the charging protection circuit 21 comprises a plurality of single protection ICs connected in parallel and a triode, as shown in fig. 4, the charging protection circuit 21 comprises three single protection ICs connected in parallel, after the three single protection ICs are connected in parallel, the triodes are connected with the total negative electrode and the charging protection negative electrode of the battery pack. Two ends of the batteries B14-B16 are respectively connected with a single protection IC in parallel, can detect the real-time voltage of each connected battery, and then control the triode in the charging protection circuit 21, namely control the opening and closing of the charging cathode channel.

The working current of the two-end voltage-stabilizing tube type equalizing line D14-D16 is slightly smaller than that of the two-end voltage-stabilizing tube type equalizing line D1-D13 at normal temperature, specifically is 5% -20% lower, wherein part of the working current is used for compensating the working current required by the connected charging protection line, meanwhile, the working current of the two-end voltage-stabilizing tube type equalizing line is greatly influenced by temperature, and the standby working current of the charging protection line has the characteristic of resistance and is irrelevant to temperature, so the influence of the ambient temperature is also required to be considered for the setting of the working current of the two-end voltage-stabilizing tube type equalizing line at normal temperature.

In the present invention, a charging performance test is performed on the modular lithium iron phosphate battery pack according to the above preferred embodiment shown in fig. 3, a charging process curve is shown in fig. 5, the charging channels of the three standard battery modules are CH11, CH12 and CH13, respectively, the charging channel of the protection battery module is CH21, and each of the standard battery module and the protection battery module has four voltages of 3.2

The V cells are connected in series, the nominal voltage of each module is 12V (actual voltage is 12.8V), the nominal voltage of the whole battery pack is 48V, and it can be seen that the final voltages converge to be completely balanced.

The charge difference between the four battery modules in the modular lithium iron phosphate battery pack in this embodiment is specifically: the total battery charge capacity in the first standard battery module 11, the total battery charge capacity in the second standard battery module 12, and the total battery charge capacity in the third standard battery module 13 are respectively lower by 0.33%, 0.67%, and 1.00% than the battery in the protection battery module 2, and thus the battery in the protection battery module 2 is in the leading position. After full charging, the voltage of the battery rapidly rises and triggers the charging protection circuit 21, and the charging path is cut off. And then, as continuous current passes through the two-end voltage-regulator tube type equalizing circuit, the voltage of the protection battery and the standard battery begins to slide. The graph shows the voltage value of the protective battery module CH21 including the voltage dropped across the line switching device.

After a few minutes, the voltage of the protection battery slides to the protection release value set by the charging protection circuit 21, the charging circuit is restored to be conducted, the battery voltage starts to rise again until the protection is triggered again, and the process is repeated for many times. Because the voltage-current relationship of the voltage-stabilizing tube is approximate to logarithmic characteristic, even a small voltage difference can generate a great current difference. The original charge difference is quickly filled. The voltage of each battery module then quickly levels out, after which the battery pack is in a completely uniform state of equilibrium. It can be seen that the efficient operation of the charge protection circuit 21 and the two-terminal stabilivolt-type equalization circuit can quickly fill up the difference.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the utility model, and any modifications, equivalents, improvements and the like made within the design concept of the present invention should be included in the scope of the present invention.

Claims (8)

1. The utility model provides a modularization lithium iron phosphate group battery with partial protection circuit that charges which characterized in that: the battery module comprises a plurality of mechanically-constructed independent battery modules which are arranged in series, wherein the battery modules comprise a plurality of standard battery modules and a protection battery module, and the protection battery module is positioned at the total negative pole position of the lithium iron phosphate battery pack; a plurality of batteries connected in series are respectively arranged in the standard battery module and the protection battery module, and two ends of each battery are connected in parallel with a two-end voltage-stabilizing tube type equalizing circuit; and two ends of part or all of the batteries in the battery protection module are also connected with a charging protection circuit in parallel, and the batteries connected with the charging protection circuit in parallel are protection batteries.

2. The modular lithium iron phosphate battery pack provided with a partial charge protection circuit according to claim 1, wherein: the total cell string number of the lithium iron phosphate battery pack is m, the string number of the protection cell is n, and 1 & lt, n & gt is & lt, 25% m.

3. The modular lithium iron phosphate battery pack provided with a partial charge protection circuit according to claim 1, wherein: the capacity deviation of all cells is ≦ 5%.

4. The modular lithium iron phosphate battery pack provided with a partial charge protection circuit according to claim 1, wherein: the working current of the two-end voltage-stabilizing tube type equalizing line for protecting the two ends of the battery in parallel is lower than that of the two-end voltage-stabilizing tube type equalizing line for protecting the two ends of other batteries in parallel in the lithium iron phosphate battery pack.

5. The modular lithium iron phosphate battery pack provided with a partial charge protection circuit according to claim 4, wherein: the working current of the two-end voltage-stabilizing tube type equalizing line for protecting the two ends of the battery in parallel is 5% -20% lower than that of the two-end voltage-stabilizing tube type equalizing line for protecting the two ends of other batteries in parallel in the lithium iron phosphate battery pack.

6. The modular lithium iron phosphate battery pack provided with a partial charge protection circuit according to claim 1, wherein: the two-end voltage-stabilizing tube type equalizing circuit comprises a voltage-stabilizing diode.

7. The modular lithium iron phosphate battery pack provided with a partial charge protection circuit according to claim 1, wherein: the two-end voltage-stabilizing tube type equalizing line comprises two diodes which are connected in series in a forward direction, wherein at least one diode is a light-emitting diode (LED) device.

8. The modular lithium iron phosphate battery pack provided with a partial charge protection circuit according to any of claims 1 to 7, characterized in that: and no discharge protection circuit is arranged in the modular lithium iron phosphate battery pack.

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