Understand the important method of battery pack cooling and heating

　　Author ：Iflowpower – UMboneleli weSikhululo saMandla esiphathwayo

For BMS, it belongs to the surrounding area; the current BMS hardware and thermal management seems to control the temperature of the water pump and collecting the water pipe, more design content is in software and the module structure, the heat simulation department. (Network) This important goal is to understand the heating and cooling of battery packs on electric vehicles. Cooling method: The wind is cold and divided into natural cooling and mandatory air cooling.

Natural cooling is to transfer the heat of the battery to the surrounding air, do not apply additional convection methods, and some extent is "listening to the sky"; basic early electric cars are this method, like the Qin, Tang, etc. Battery pack (below) is from the network);. Forced air cooling is added to the fan, manufacturing a convective working condition, air flows through the battery surface with a certain flow rate, takes heat to the external environment; this will involve the airway, the field design, the selection of the fan Position and other problems; this method also more than an early electric vehicle or energy storage module; such as Renault ZOE battery module, the hole in the middle of the sealing is in the air, the other two is the air outlet (the following figure is from The internet).

Liquid cold liquid is cold in direct contact with indirect contact. Direct contactless liquid is cold in the cooling of the cell (eg, silicone oil), this method has heard that the microavogenic power has, but I didn't find specific cases, less application. Indirect contact is the current cooling method of the mainstream battery pack, refers to a metal plate between the battery and the coolant, and complete heat exchange through this metal plate.

The liquid cooling system (air conditioning cooling) that is often used in the battery pack is interactive, as shown in the figure below: The power lithium battery passes heat to the coolant (water + ether alcohol) through the metal plate, and the cooling liquid will The heat passes the heat exchanger to the cooling system of the whole vehicle, completes the transfer of heat; there are two heat exchanges in this process. (The picture is from the automotive school) Cold Media Direct Cold Media Direct Cold Interpretation of Refrigerant Gas-Liquid Change Cooling, it is the principle of heat-conducting by refrigerant transforming into gaseous gaseous; in fact, this is the principle of air conditioning refrigeration, as shown below: The picture below shows a typical battery pack. The picture is in parallel with the car schools.

It is parallel with the cooling system evaporator of the whole vehicle. It will be arranged in the battery pack, in fact, an evaporator, internal refrigerant There is a transformation of liquid to gaseous; then shared compressor, concurrent part of the air conditioner. Usually, the cold-cooling method of the refrigerant is to take BMWI3: it places a cold plate (evaporator) at the bottom of the battery module, used to carry out the heat exchange of the module and the refrigerant, the refrigerant uses R134A; overall and liquid cooling method arrangement almost.

In addition, there is a phase change material cooling method, which is very small. Heating method: The heating film heating film is generally composed of a resistance wire, an insulating cladding layer, and a lead (from the network); the resistance wire is typically a nickel-chromium alloy or a ferrome alloy; the insulating coating is generally polyimide. (PI film), silica gel and epoxy resin.

The heating film principle is hot after electrical resistance, and it can be attached to the outer casing of the module in the battery pack; a plurality of heating films are connected in series or in parallel, and the battery pack is powered by the battery pack, and the power switch is controlled by the BMS control relator power switch. PTC refers to heating the PTC directly in contact with the battery or module, similar to the heating film method; PTC refers to the temperature coefficient resistance, and the temperature is also increased, so that it limits its heating power. , Eventually reach a steady-state temperature, safety is better; in the same manner, high voltage battery is also powered; on the structure, it is necessary to do insulation and thermal conductivity; PTC method is thicker than heating film.

Liquid heat liquid is hot in the hardware of the liquid cooling method, heating the coolant to achieve a further heating battery; specifically, as shown below (picture from the car school), in parallel all the way in the battery pack liquid cooling system When heating, the cooling liquid flow through the three-way valve is controlled by the heater, and then circulates it through the water pump to flow through the metal plate at the bottom of the battery, and heat the battery; wherein the heater is generally in the form of PTC. The principle of fever is the same as the previous PTC. In addition, the heating method also has hot air PTC, heat pipe, heat pump, etc.

, which are relatively small.