Only jumping out of the dedicated IC method battery management system innovation can be expected

2022/04/08

  Author :Iflowpower – Portable Power Station Supplier

The emergence and development of battery management dedicated IC is related to various problems encountered during the use of lithium-ion batteries. First, in order to solve the overcharge of the lithium-ion battery, the charge and discharge protection chip of the single-section battery was designed. Later, it developed in the use of multi-section in the lithium-ion battery, and it became a multi-string chip.

At this time, it became Battery management chip, tightly collect each battery voltage data in the battery pack. Further, in order to cope with the problem of inconsistencies, the driving function of the power switch is further integrated, which is a battery management IC with equalization. Objective speaking, battery management dedicated IC scores have earned early BMS industry, and also leads the development of BMS products.

It is because there is a special chip, BMS design can be greatly simplified, and the miniaturization and reliability of the product have greatly improved, but at the same time, we must also see the limitations of special chips. As mentioned earlier, the battery management dedicated chip is also developed with the use of lithium-ion batteries, and early lithium-ion batteries are used in small electronic devices, and later are widely used in laptops, to this battery management dedicated chip has always been for Low strings, small equipment services. When the lithium-ion battery pack is used to electric car, the situation has changed.

Electric vehicle lithium ion battery pack is a high string, large-capacity battery is used in series, and the number of tens of strings even hundreds of strings are no longer a series of series of serialized lines in laptops. The dedicated IC has not been idle, and quickly introduces more strings used, but considering the voltage and use complexity generally no more than 20 strings. Typical architecture of BMS using these ICs is a gathering architecture.

Only between BMS and battery packs, the number of wirings depends on the number of battery packs, and the number of special chips on the BMS board is also dependent on the number of battery packs. As can be seen from the schematic, the advantage of aggregated BMS products is simple, low cost. When the number of battery packs is low, for example, 10 are string, the connection is not very complicated, and in the case where the battery pack capacity is small, the BMS installation location can be close to the entire battery pack, shorten the wiring distance, battery pack - --- BMS, the entire energy system is more compact, more suitable on electric bicycles and electric motorcycles.

However, when the electric vehicle lithium-ion battery pack is used, because the battery capacity is large, the physical dimension is relatively large after the group, the connection will be longer, and the length is not very, plus the number of strings, there are many , Dozens of or even the arrangement of hundreds of lines is very troublesome. There is also a tight detail that the order in which these connectors is to be fixed because the pin of the special chip has already implicitted the sequence of the battery in advance, so the connection to the BMS is to be accessed by the connection. Although this is not difficult in BMS design, it is a small trouble in the actual connection between BMS and battery packs.

The general line is both one end and the battery, and the other end is connected to BMS through the plugin. It is also difficult to complete with the battery. It is also difficult by the machine to complete the machine, connected to each electrode of each cell.

Can't make any mistakes, this whole workload is ideally. Through the decomposition of the aggregation architecture, we see that the dedicated IC is more suitable for small capacity, low strings, in large capacity, high strings, there will be complex, and to have a different point of view. Re-seeing the problem, the aggregation architecture is more suitable for completing passive balance, the circuit design does not increase the complexity, and the mainstream dedicated IC of this chance has this function.

However, the current capacity is limited, the level of half-hour, the problem is not very different in the case of the initial consistency of battery packs, and there is a risk of unbalance correction of battery imbalance in the case of neutral consistency. If you want to join an active balance function, the existing architecture basically does not help, the extra harness and switch matrix, the complexity of the circuit has risen sharply. The switch matrix should have a large number of electronic switches, but because of the number, the control circuit is quite complicated, and the company is replaced by the relay, simplifies the design, but bringing the relay as a mechanical switch to life problems and misunderstand risk.

Of course, it is also possible to extend its life by lowering the switching frequency of the relay, avoiding risks through malfunction inspection, but doing so, it is always unable to ensure that the device's uniform failure work time, and more, the number of relays is quite quite, more than one. This is a way to make a step, not the positive solution of processing active balanced switch matrix problems. In order to solve the complex challenge of the connection, BMS of the distributed architecture appears.

This BMS is separated from other functions to other functions, and the entire system is divided into CSC (single management unit), BMU (battery management controller), and CSC is installed on a single battery, responsible for this string battery information collection And transfer, each string of battery is incorporated into BMU through the bus. This architecture processes the complicated challenge of harness through the bus, and the installation is relatively simple, high efficiency, good flexibility, suitable for different battery packages. Distributed BMS can not use battery management dedicated IC, which is a relatively successful idea for the purpose of innovation design.

Insufficient, the distributed architecture has not dealt with a corresponding relationship and active balanced problem. The CSC also sets the address (although it can be set after installation, it is easy to implement before installation, error probability Small), active balance still needs additional harness and switch matrix. Moreover, because each CSC is MCU and with isolated communication bus, the price is higher than the aggregation architecture BMS, especially in the low stroke number.

Distributed ideas gave a good tip of aggregation, this is through bus processing harness problems, dedicated ICs also saw the benefits, quickly launched a communication bus with no isolation, further improved themselves. Semi-distributed architecture, actually the secondary aggregate architecture became one of the mainstream design of BMS. This is to divide the entire battery pack into several modules.

Each module uses a small BMS designed with a dedicated chip, and then connects to a final controller through the bus. The semi-distributed architecture aggregates the advantages of distributed harness and aggregation design simple advantages, but unfortunately, the problem that the previous architecture has not been dealt with inherited, and the relationship between the one-one correspondence and the active balanced problem is still exist. Chasing the source, one-to-one correspondence, the problem of switch matrix in the active balance, from the conventional limitations of the battery management special chip, although the battery management special chip is also evolving.

Because it is a multi-train, on the dedicated IC, each battery test channel does not have to determine the number, afterwards, after the order, the order of each channel cannot be imagined, and now see any ICs can not design such a function. Similarly, the switch matrix is ​​also derived from a multi-train, but also because of the power part, this is the natural weakness of IC, and the existing architecture is the reason for the active balance. Therefore, if it is a low string, there is no need to actively balanced the function, and the special IC method is feasible, such as electric tools, electric bicycles and electric motorcycles; in the use of electric vehicle levels, especially the active balance function, Design BMS in a dedicated IC is still more.

From the production of 2015, the electric car has successfully completed the introduction period of the industry, followed by the development period. BMS urgently needs to handle the disease, the market shouts new products, only the special IC method is jumped out, BMS innovation can expect. .

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