# How Car Battery Modules Combine High and Low Voltage Systems > A self-contained battery module that houses both high and low voltage batteries, a power converter, and safety switches in a single unit designed for efficient heat management. - **Patent:** US 6828755 - **Original title:** Battery system module - **Owner:** Johnson Controls Technology Co - **Granted:** 2004 - **Status:** Public domain (expired) - **Times cited:** 46 - **Field:** automotive, mechanical, energy ## What it does This patent describes an integrated battery module for vehicles that packs a high-voltage battery (for heavy loads like motors) and a low-voltage battery (for electronics) into one container. It includes a DC-to-DC converter to move power between the two batteries and safety switches that automatically cut power if the container is opened or a service door is accessed. The design also features specific cooling paths and apertures to move heat out of the box, ensuring both the batteries and the converter stay within safe operating temperatures. ## What it does NOT cover - Does not cover battery systems that lack an integrated DC-to-DC converter. - Does not cover systems that rely solely on liquid cooling rather than the described air-flow paths. - Does not cover battery modules that do not include a safety disconnect switch triggered by opening the container or a service door. - Does not cover standalone batteries that lack a secondary low-voltage battery within the same housing. ## The clever bit The invention treats the entire battery module as a single, modular unit that includes its own safety interlocks and thermal management, rather than treating the battery, converter, and cooling system as separate, scattered components in the car chassis. ## Real-world examples 1. Early 42V/12V hybrid vehicle electrical architectures 2. Integrated battery management units in modern hybrid electric vehicles 3. Modular automotive power distribution systems ## Why it matters This patent addressed the early engineering challenges of transitioning to hybrid and electric vehicles, where managing two different voltage levels in a compact, safe space was difficult. By integrating the converter and safety disconnects into a single module, it helped standardize how manufacturers could package power systems for better reliability and easier maintenance. ## Frequently asked questions ### What does How Car Battery Modules Combine High and Low Voltage Systems cover? A self-contained battery module that houses both high and low voltage batteries, a power converter, and safety switches in a single unit designed for efficient heat management. ### Who owns patent US 6828755? Johnson Controls Technology Co owns this patent, granted in 2004. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 6828755 cited by? This patent has been cited by 46 later patents that build on its ideas. ### What problem does this patent solve? This patent addressed the early engineering challenges of transitioning to hybrid and electric vehicles, where managing two different voltage levels in a compact, safe space was difficult. By integrating the converter and safety disconnects into a single module, it helped standardize how manufacturers could package power systems for better reliability and easier maintenance. ### What does this patent NOT cover? Does not cover battery systems that lack an integrated DC-to-DC converter. **Full plain-English explainer:** https://patentbrief.org/patent/us/6828755/battery-system-module **Original patent:** https://patents.google.com/patent/US6828755 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How a Hybrid Layer Stops Metal Growths in Lithium Batteries](https://patentbrief.org/patent/us/10566652/lithium-metal-battery-with-hybrid-electrolyte-system) — This patent describes a special multi-layered electrolyte system for lithium metal batteries that uses a stiff, hybrid material to block dangerous metal growths, aiming for safer, higher-energy batteries. - [How Electric Cars Safely Pause Charging When You Want to Unplug](https://patentbrief.org/patent/us/9379564/charging-control-apparatus-and-charging-control-method) — A system for electric vehicles that safely pauses power flow when a driver signals they want to disconnect the charging cable, preventing electrical arcing or damage. - [How Devices Negotiate Power Sharing When Connected Together](https://patentbrief.org/patent/us/9874914/hololens-mixed-reality-display) — A system for host devices like laptops to automatically set and update power-sharing rules with connected accessories based on identity and real-time power needs. - [How Boeing Stacks Electric Space Vehicles for Launch](https://patentbrief.org/patent/us/11708181/mechazilla-catch-tower) — A design for a launch vehicle that carries two space vehicles stacked on top of each other, both using electric propulsion systems for movement in space. - [Boosting Fuel Cell Power for Vehicles Using Oxygen Injection](https://patentbrief.org/patent/us/5346778/electrochemical-load-management-system-for-transportation-applications) — A system that boosts a vehicle's fuel cell power by injecting pure oxygen into the air supply when the engine needs extra energy.