The ChevroletBolt EV, which went on sale in 2016, is a decisive product of GM in the era of electrification, and this is the best result that GM has explored in the field of electric vehicles for many years. Of course, if it is not Model3, Bolt EV will not come out so quickly, because if it does not include the relevant subsidies, GM will lose money to sell every BOLT EV.
Here we do not analyze its economy, focusing on its battery system technology, after all, this 60-degree battery, 238-mile battery pack is very impressive.
In addition to the earliest EV1, from Chevrolet Volt (1st generation / 2nd generation), Malibu, SparkEV, to today's Bolt, GM continues to develop in electric vehicles. A large part of BoltEV's technology is derived from SparkEV. The picture below shows the evolution of its battery pack.
The Bolt battery pack has a rated voltage of 350V, a total power of 60kwh, a total weight of 435kg, 285L, and a specific energy of 138wh/kg; the maximum output power of the battery pack is 150kw. Compared to SpakEV, the system-level specific energy is increased by 80% (SpakEV battery pack total power 20kwh, weight 260kg).
Bolt's battery pack consists of a total of 288 cells, in groups of 3P96S. The warranty for the battery pack is 8 years / 100,000 kilometers, and the battery attenuation is officially given in the range of 10 to 40% (8 years). However, 40% is generally rare, GM's thermal management is doing very well, and Volt's first generation products have never replaced batteries due to battery attenuation.
BoltEV uses LG Chemical's soft-packed batteries. The parameters of the battery are not given by GM and LG. The data shows that the nominal voltage is 3.6V and the rated capacity is around 58Ah. Type nickel-rich Li-ion .
The entire battery pack is located on the chassis and is a typical skateboard.
The battery pack is divided into five major areas, each with two modules. In order to make full use of the internal space of the battery pack, Bolt's cells are placed horizontally (the width of the battery is 338mm, the height is 100mm; the VOLT and SparkEV are placed vertically); at the same time, the heater is not integrated in the battery pack.
The electrical connection between the module and the module is made by Busbar, which forms the high voltage circuit in the whole PACK; the maintenance switch (MSD) is at the top of the rear end to disconnect the high voltage circuit from the whole vehicle when needed.
The high-voltage control box, called BDU (Battery Disconnect Unit) in the BoltEV battery pack, is responsible for relay control, current monitoring and other functions. It is guaranteed to be safe and stable when the power is on at high voltage, and at the same time ensure the insulation of the electric chassis. The current monitoring of the entire PACK provides data for the SOC and SOH.
In terms of thermal management, the BoltEV battery pack uses active liquid cooling and heating, a technology that has been used since Volt. In general, thermal management should be done: (1) battery pack cooling / heating performance; (2) warm-war, warm-up heating rate and heat transfer efficiency. In order to make the battery pack in the best ambient temperature in the hot and cold conditions. To this end, GM evaluated six thermal management options before and after.
The cooling system circulates to each module and each structural area; there is a cooling fin between each two cells, and the cooling fins are connected to the cooling plate. At present, the cooling system of BOTLEV has not been dismantled. The figure below shows the cooling yarn structure of VOLT2 for reference.
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