Does Model 3's PCS have a two-way design and V2G direction?

Introduction: I saw several public accounts reporting a few days ago (actually from Electrek, it is believed that an engineer Marco Gaxiola's analysis and evaluation showed that the PCS hardware has achieved bidirectional functions). For this reason, Phil Sadow, a comrade of "Ingineerix" who has a reputation in Tesla dismantling and cracking, released videos at both ends and explained the problem in detail. In terms of rectification, the OBC output rectifier tube fast recovery diode was treated as a silicon MOS tube, so there was an erroneous judgment that led to a series of car crashes. However, looking forward, it is not a big problem to modify the PCS. If the battery can really be used for 1 million miles, and the car cannot run to the V2G launched in various places, it will be worth doing in the future.

01 The current PCS is not designed with bidirectional functions

Ingineerix explained it very clearly, so I won't elaborate further.

Mainly talking about this schematic diagram: Marco Gaxiola's reverse analysis of the Model 3 on-board charger OBC is a bit amateurish. I didn't look carefully at the silk screen on the PCB, which all starts with D (Diode), and the device name is TH30R06. The MOSFET tube of the LLC at the front end is labeled 36N60DM6.

Figure 1: Wrong part (red) in the main circuit diagram of PCS 

We need to further explore Tesla's design of Sentry Mode and pre-charging in the future. These strategies are easy to OTA, so according to the current Benchmark situation, it can be adjusted and the power-off time can be adjusted according to the needs of electrical appliances. 

02 Million-mile batteries and future V2G

We need to understand that V2G itself is to help the power grid in China, and then share some benefits with you. Here are a few things to make clear: 

1) The power grid needs to be robust, so it cannot be available sometimes and not available sometimes. If this is the case, it is better for China's power grid to not have it. It can consider more certain distributed power grids, such as solar storage and charging, which can be controlled. Who knows whether the mobile car is there? 

2) The money that can be made is limited, and once all cars in a certain place can make money through V2G, the power grid will basically have to transform that place, because this is not a wool-pulling thing, and the investment in the power grid is definitely more cost-effective than constantly distributing money. 

3) In China or most regions, electric vehicles are an indispensable part of the power grid ecosystem. Simply put, if you reach a certain scale, you must be orderly and controllable, otherwise I will not allow you to charge and connect to the grid. Sometimes you want 11kW (AC fast charging), and sometimes you don’t want it. This year, the grid will complete the orderly charging work in the pilot residential areas, and in 2020, it will start large-scale promotion and application based on feasibility and economic demonstration. This is worth paying attention to. 

Figure 2 Solving the problem of orderly charging and charging time management is a top priority 

For automobile companies, the life of the battery cell is actually directly related to the residual value. Let's do the math. Electric cars are first and foremost a means of transportation. We will calculate how much gasoline is used per 100 kilometers and how much it is worth; how much electricity is used per 100 kilometers and how much it is worth. What is obvious is that electricity is much cheaper than oil. If consumers are not allowed to feel how many kilometers they can use, and in the future when they sell cars like useless batteries, they will use this psychological superiority to make a profit from the price difference in electricity (0.3 yuan per kwh and the throughput is doubled). This is simply not logically tenable. Note: The power grid has peaks and valleys. The solution to this problem of peak and trough electricity consumption using a dedicated energy storage system cannot be calculated in the short term, but it may be soon calculated in the LFP system.

Summary: China has already started to design topologies with V2G and V2V as a standard, but the core issue involves all aspects of safety. My understanding is that since there is a charging efficiency calculation factor in the power consumption of electric vehicles, in the short term we will still focus on charging efficiency to integrate SiC devices and balance cost and efficiency. Moreover, V2G also involves other problems caused by not using PLC communication, such as the possibility of misidentification of wireless communication piles and vehicles. This matter is not something we can solve in a few words, and whether Tesla's CAN-based approach can be universal is also a potential question mark.