lithuim ion battery 18650

　　Model 3 lithuim ion battery 18650 management system re-analysis

　　After rearranging the circuit schematic diagram of Model 3, and re-looking at the interface and structure of the lithuim ion battery 18650 management system of Model 3, we can see that the lithuim ion battery 18650 management ECU unit has been simplified during the evolution process.

　　This is actually caused by the differences in management and control of the entire EE system. This article will analyze these changes from several small aspects.

　　01lithuim ion battery 18650 management system interface

　　Overview

　　The picture below is my decomposition through the circuit schematic diagram. The entire lithuim ion battery 18650 management system is mainly connected internally to the fast charging connector, temperature sensor, positive and negative contactors, current sensor, controllable fuse, and internal PCS (DCDC and OBC). Unit daisy chain CMU controller, as well as externally facing power supply unit, external HVIL circuit, charging control board, powertrain CAN.

　　This can actually correspond to the connector of the internal lithuim ion battery 18650 management system, as shown below:

　　P1 (VEHICLEINTERFACE): 18 pins in total, including two CAN channels (PTCAN and CPCAN);

　　P2 (EXTLOWVOLTINT): This signal pin is mainly used to connect the PCS internally and detect the internal connector. The Hall temperature sensor is also inside, so that the numbers can be correct;

　　P3 (SHUNTINT): connected to the current shunt P4 (HVSENSE): high-voltage sampling connector, which collects the high-voltage circuit and divides it to the upper high-voltage processing circuit. It mainly contains three contactors (main positive, main negative and fast charging twin contacts (contactor), the high-voltage acquisition circuit here is nominally 3 inputs, but in fact there will be crossover between the main positive and main negative contactors for diagnosis;

　　P5 (ABMB) & P6 (BBMB): daisy chain output and return lines, used to connect each CMU;

　　P7 (PYROLOOP): Control loop that can cut off the fuse.

　　02 High voltage sampling and contactor diagnosis

　　area of high pressure section

　　According to the above definition, the fast charging contactor group uses auxiliary contacts to diagnose adhesion, and the main positive and main negative itself need to collect the internal and external Buslink voltage and output voltage, so in principle, the minimum number of high-voltage sampling circuits is only 3 groups. If the high voltage acquisition across the positive and negative contactors increases again.

　　Note: If I want to make this circuit smaller, the core idea is to reduce the number of sampling channels.

　　03Changes in HVIL

　　The difference between inside and outside

　　As shown in the figure below, we can really see the benefits of integration. Looking at the HVIL circuit alone, and the classic system circuit of the MY2012 Model, the original DCDC and front-end power distribution functions are integrated into the lithuim ion battery 18650 Inside the package, the coolant heater is replaced by integrated thermal management and motor waste heat recovery.

　　The 12VFuseBox is further integrated (I want to talk about this separately with the electronic fuse); the charger and the HVJunctionBox behind it are integrated into the lithuim ion battery 18650 system. It turns out that the AC-side design of 10kW+10kW was replaced by a strategy that focused more on DC fast charging.

　　The entire circuit becomes as shown in the figure below. The HVIL high-voltage interlock physics is for the bus harness connector of the high-voltage circuit. It is divided into three, the HVIL circuit 1 (an external set of connection circuits) connected to the outside of the vehicle, the internal High voltage connector HVIL2 (contains three connectors inside) and fast charging high voltage harness and connector integrity.

　　Depending on the definition, two sets of analog signals and one set of PWM signals are also used in different ways to manage the results of real-time and continuous monitoring of the high-voltage circuit in real time and identify them through the vehicle diagnostic system. The design idea here is to separate several interfaces, so it can be easier to distinguish where problems occur and locate them.

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