Patent AU-2020281282-A1 (AU)
Title: Temperature controlled battery pack bath tub (BPBT), and a method of protecting a large battery pack from thermal stresses
Inventor: GUPTA SANJAY
IPC: H01M10/6569
Filed: 2020-05-27
Abstract: Battery packs are used in large electric vehicles e.g. cars, trucks, buses, vans, trains, boats to supply high voltage power to electric motors. These can also be used as backup power unit for hospitals, data centres and industrial units. This Battery pack is designed as bath tub like container, with a watertight lid. An apparatus of Battery pack bath tub (BPBT) (100) is designed to hold a plurality of battery modules (BMs). The BPBT is a large bath tub like container (101) filled with 2 phase (liquid and vapour) dielectric liquid. BPBT is a closed container with a lid (102). BPBT is designed to hold vertically and horizontally stacked BMs; and associated electronics (e.g. battery chargers, battery controllers etc), fully submerged in the dielectric liquid. The inclusion of associated electronics is optional. The BPBT is thermally connected to a heater and also thermally connected to a condenser. The BPBT is electrically modular, and any number of modules can be electrically connected in series or parallel. In this innovation the BPBT provides: a. homogenous temperature environment for high density modules; b. cooling of the BMs and the associated electronics, in hot and extremely hot temperatures; c. heating of the BMs and the associated electronics in the cold and extremely cold temperatures; d. protection from flooding to the BMs and the associated electronics. The method of protecting a large battery back from thermal stresses is explained through an example of the Battery pack which is designed as bath tub like container, with a watertight lid. A Battery pack bath tub (BPBT) (100) is designed to hold a plurality of battery modules (BMs). The BPBT is a large bath tub like container (101) filled with 2 phase (liquid and vapour) dielectric liquid. BPBT is a closed container with a lid (102). BPBT is designed to hold vertically and horizontally stacked BMs; and associated electronics (e.g. battery chargers, battery controllers etc), fully submerged in the dielectric liquid. The inclusion of associated electronics is optional. The BPBT is thermally connected to a heater and also thermally connected to a condenser. The BPBT is electrically modular, and any number of modules can be electrically connected in series or parallel. In this innovation the BPBT provides: a. homogenous temperature environment for high density modules; b. cooling of the BMs and the associated electronics, in hot and extremely hot temperatures; c. heating of the BMs and the associated electronics in the cold and extremely cold temperatures; d. protection from flooding to the BMs and the associated electronics. A Method of protecting a large battery pack from thermal stresses, is claimed. A method of providing flood protection to a large battery pack, is also claimed. A method of cooling the battery pack in extreme hot temperatures, is also claimed. A method of heating the battery pack in extreme cold temperatures, is also claimed. Typically a group of batteries are arranged in a module, and a number of such modules are joined electrically in serial and parallel, to create a battery pack with large energy capacity. In this invention, an apparatus of Battery module (BM) (200) is designed to hold plurality of rechargeable batteries and capacitors, arranged in one or more groups. Each group of batteries are electrically connected in a serial or parallel fashion with the other group of batteries. Each group of capacitors are electrically connected in a serial or parallel fashion with the other group of capacitors. The capacitors are optional. The BM is designed to be fully submerged in a 2 phase (liquid and vapour) dielectric liquid. The batteries and capacitors inside a BM are arranged to create ducts and create a vertical flow of dielectric liquid through these ducts. These ducts act as heat exchangers. The process of subcooled flow boiling is used to cool the batteries/capacitors. In cold weather conditions, these ducts are also used to transfer heat from the heated dielectric liquid to the cold batteries/capacitors. A method of repurposing the battery module (BM) is also claimed. Charging and balancing circuit is one of the key components of the battery pack. An apparatus to charge a battery pack is a balanced charging circuit (300), and a balance charging algorithm which calculates 'Balanced SoC' for batteries and 'Balanced voltage' for capacitors and selectively charge batteries and capacitors based on that calculated balanced SoC and balanced voltage respectively. The balanced charging circuit has further four key sub-components - Battery pack controller which is made up of hardware and software; converter which converts AC/DC to DC; Battery/capacitor charge controller which acts as a slave to the Battery pack controller; and an Energy charging split circuit which also acts a slave to the battery pack controller. The battery pack controller's algorithm takes into account the SoH of the batteries, e.g. if a module's SoH (the remaining capacity) has degraded to 95% as have batteries aged, while other modules are still at 100%, all the modules are selectively charged to SoC of 95% using a specific voltage and current. This balanced charging circuit and balanced charging algorithm, decouple the input voltage from battery pack'soutput voltage. Thus the battery pack can be charged at any voltage and is agnostic to the battery pack output voltage. This also speeds up charging process by not going through stop/ start process of charging and balancing through removal of charge from the over charged batteries. A method for charging, and decoupling the charging voltage from the battery pack voltage, is also claimed. Battery packs are used in large electric vehicles e.g. cars, trucks, buses, vans, trains, boats to supply high voltage power to electric motors. These can also be used as backup power unit for hospitals, data centres and industrial units. In this innovation a hybrid battery module (BM) combines the SoC of lithium ion batteries with the SoC of the capacitors to meet the current demand of the BM. This innovation creates a hybrid battery BM where capacitors of the BM supply the current when batteries within a BM are discharged to minimum SoC levels. This extends the range of the battery pack. This hybrid BM also uses capacitors to supply the peak current, and batteries to supply the average current. This also extends the range of the battery pack, as batteries deplete faster through peak currents and more of the regenerative energy is optimally used. As the BMs do not deteriorate equally with age, this innovation selectively instructs each BM the optimal mix of batteries and capacitors current. The invention constitutes an apparatus of Energy discharging split circuit installed within each BM, and an energy management algorithm installed in the battery pack controller. The energy discharging circuit mixes the current output of batteries and capacitors within each BM, as per the instructions from the battery pack controller algorithm. The algorithm takes the SoH and SoC of the batteries in the weakest BMs into account to calculate the mix of current from batteries and capacitors, and selectively instructs each BM. A method for discharging the battery BMs, and extending the range of the battery pack, is also claimed. Battery pack controller is the Master controller of the battery pack. The Battery pack controller: a. provides safety from high voltage in the event of an accident, or repair of the electric vehicle; b. automatically takes out a failed battery module (BM) out of the electrical series circuit, so that the whole of the battery pack does not require replacement because of a failed BM or a group of failed BMs; c. automatically puts out the fire and removes the smoke in the event of thermal runaway and fire. d. communicates with the user of the battery pack regarding the failure of the BMs.