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BYD's immersion-cooled cabinet filing routes wiring through the top of the coolant to ease pressure on seals
BYD's cabinet patent filing, published October 5, 2026, submerges battery modules in dielectric fluid and routes their wiring through the top of the bath. Its focus is the boundary where those cables pass from the wet chamber to the dry electronics above.
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Drafted by a language model from the sources cited here and checked against its claim ledger before publication. How we use AISend a correction
What happened
- BYD filed the application in March 2025, about 19 months before China's patent office published it as CN 122868832 A.
- Electrical equipment sits in a dry upper chamber and the battery modules sit in a wet lower chamber beneath it.
- BYD's existing MC Cube-T storage system specifies liquid cooling, while CATL's EnerOne and EnerC put cooling plates outside the modules.
- The application covers battery cabinets and energy storage equipment and does not identify any passenger-vehicle use.
- The application is still under substantive examination, and BYD has announced no commercial production plans for the cabinet.
Compiled by The Product DeskSomething wrong?How this is made
Why it matters
- exposure With electronics stacked over the bath, the boundary crossing is where a leak would reach parts never meant to be wet, so inspection and service plans for such a cabinet would center on that seal.
- constraint Read narrowly, the filing is evidence about BYD storage cabinets only, and car buyers should not infer immersion-cooled BYD vehicle packs from it.
- decision Anyone buying storage now is still choosing among existing liquid- and plate-cooled products, since this cabinet exists only as an application.
Interesting Engineering, which reported the filing, put the problem in its first line: "Cooling battery cells directly in liquid creates an engineering challenge: keeping that liquid away from electrical equipment." [14] I think whoever has to sign off on one of these cabinets will rank their worries the same way. According to the same report, the application's focus is the boundary between the wet and dry chambers, where connections must pass through without letting coolant reach components meant to stay dry [5].
What gets pitched with immersion is the heat path. In many battery systems, liquid runs inside aluminum cold plates set against the modules, so heat has to cross the cell casing and the materials between cells and plates [6]. Submerge the modules in a non-conductive fluid and heat moves from their wetted surfaces straight into the liquid, giving a shorter thermal path [7]. BYD specifies the fluid by type, including hydrocarbon- or ester-based dielectrics that insulate the modules electrically while cooling them [8].
What the filing actually works on is containment. Once the cells are wet, holding the fluid in becomes part of the cabinet design, and connection points not meant for immersion still need protecting [7]. BYD keeps the electrical and signal lines out of the floor and the deeper sections of the bath [9]. Hydrostatic pressure rises with depth. A sealing interface near the top of the fluid has less liquid pressing on it than one near the bottom [10].
The evidence supports a narrow version of the idea that the crossing, more than the cooling, is the hard part. The published account does not include temperature or pressure figures, so it shows where BYD put its design effort [5] without showing how well that seal performs.
For a team weighing an immersion cabinet against a plate-cooled one, two questions sort the options. The first is whether the cells sit in fluid at all. If they sit against cold plates, there is no wet chamber for wiring to cross, and the comparison stays on heat transfer [6]. The second, for wet designs, is how far below the fluid line the cables leave the bath. A crossing near the surface puts the least liquid pressure on the seal [10]. A crossing through the floor puts the full depth of the bath on it [10], and a vendor offering that layout should be able to say why it passed on the high crossing BYD filed [1].
What to watch
- Whether China's patent office grants CN 122868832 A after substantive examination, and whether the claims covering the wet-to-dry crossing survive intact.
- Any BYD test data on seal performance or cell temperatures for the immersion cabinet.
- A BYD announcement placing an immersion-cooled cabinet in its storage line next to the liquid-cooled MC Cube-T.