Until now, battery pack production has followed the same basic procedure. A company that specializes in making battery cells like Panasonic or LG Chem makes the individual cells and then the automakers take these cells and package them into a battery pack. In other words, the cell production is a wholly separate process from making the pack that goes into the car.

Tesla’s patent application describes a new approach where battery pack parallel subgroups are made integral to the cells themselves. In the old case, single battery cells come out of the battery cell plant. In the Tesla patent application, parallel cell groups come out of the cell manufacturing plant. It’s not really a cell manufacturing plant, but instead, it's a battery submodule (usually a parallel cell group) manufacturing plant. What pops out of the plant looks like the figure below.


                         An integrated cell group comes out of the battery plant instead of a single battery cell.

As you can see from the figure, what looks to be a circuit board is now used as a current collector and this circuit board also contains other functions such as cell balancing, overpressure, and fuse protection [0034] and [0035] (Note the numbers in brackets refer to the same item in patent app). This cell group then becomes a building block and can be connected sort of like Lego blocks to make the full-size battery. These basic cell groups can be connected in series or parallel (bigger battery packs have more cells in parallel) [0030] and [0050]. The collector plates/circuit boards can be on both ends or just on one end [0029]. The circuit board collector plates also double as end caps to the cell [0031]. They seal the cell. Elecrolyte is added prior to sealing the cell with the circuit board collector.

You can see that in this new process the collector plate/ circuit board becomes integral to the cell manufacturing process. It isn’t added after the fact as in current day methods.

Outside of the basic cell group manufacturing area, the parallel cell groups/Lego modules are connected together and placed in the appropriately sized container to form the battery pack.

How are the cells cooled?

In one embodiment, a di-electric fluid is passed through the module. You can see the inlet and outlet in the following figure.


                         A dielectric fluid flows through the module to cool the cells.

In another embodiment, the cells are coated with an electrically insulative coating and the fluid need not be di-electric [0040]. Cooling fins could be made integral with the cell can [0040].

In another embodiment, a potting material that changes phase could be used in between the cells. The potting material changes phase at the temperature that you wish to hold the cell. A second phase change at a higher temperature could be used as thermal runaway protection [0044]. A secondary cooling loop would interface with the potting material. The cooling channel for this secondary coolant could be integrated into the cell can itself [0042] or in the case described earlier (no potting compound), cooling fins could be integrated into the cell can. Thus, even more of the pack design is integrated into the cell manufacturing part of the operation. Using a phase-change potting compound would also allow sizing of the HVAC equipment for average, not peak loads [0043].

Envisioning Tesla’s proprietary battery line

What happens when we mix this new process with Maxwell’s dry electrode manufacturing process and Hibar’s equipment manufacturing business?

Tesla’s line of new batteries? A highly simplified, more efficient and lower-cost way of making battery packs.

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