Chevy Bolt Batteries and BMS

To get more driving range the batteries were upgraded in early 2021. The upgrade batteries used are the Chevy Bolt 5.94kW-h module shown in the picture below. These modules are made by LG Electronics and are NCM (Lithium Nickel Manganese Cobalt Oxide) chemistry. Each module has a 180AH capacity and the 9 modules that will be used gives a 53kW-h battery capacity. For a 85% discharge that provides 45kW-h of driving capacity. At the measured power consumption of 292W/mile by the vehicle that capacity should provide just about 155 miles driving range. A great feature of these modules is that they are already wired for a Battery Maintenance System (BMS).  Each module has 10 cells and there are connections to each cell on the module.  The connections are on a pair of connectors at one end of the module. The Chevy Bolt uses a central processing unit for the battery maintenance so in the Bolt each battery module has a pair of cables that runs back to the central controller. The cables with the corresponding connectors already attached were obtained form Chevy Parts Online and used to make cables to connect to a local BMS controlling circuit. Each battery module will have its own BMS controller. This is easier than running wires from each module up to the engine compartment. Although between the wires from one module the most voltage would be 42V (full charged battery) the wires will have the full pack voltage, with respect to ground. Local BMS control will be safer at this point in the 320e build.  A BMS demo board, the DC2259B made by Analog Devices was initially tested to use for the module BMS.  The connections to the battery module and a BMS demo board are shown in the second and third photos below.  Although the new batteries are bigger and weigh more than the CALAB cells the new batteries will only increase the weight of the car 100 lbs but increase the driving range by 2 times!

BMS connection on battery module.  These connectors were obtain from a Chevy Bolt battery wiring harness that was purchased online.

Two connectors are required to connect to all the battery cells in the module. A DB25 connector is used for the wires coming from the battery module to make connection the BMS demo board.

 DC2259A BMS demo board that demonstrates the LTC6811-1 BMS integrated circuit.