About Promethean
Promethean is a product line built to keep Gen-1 Chevy Volts and Cadillac ELRs on the road — using modern cells, documented builds, and decision-grade performance data.
About the Builder
Promethean Batteries are built by Monroe Lee King Jr., an independent EV battery builder focused on keeping Gen-1 Chevy Volts and Cadillac ELRs on the road. Monroe’s background is hands-on across mechanics, electronics, and diagnostics — the kind of experience you only get by tearing systems down, rebuilding them, and making them work in the real world.
The shop approach is simple: build it like it has to survive. That means documented assembly, clean integration, and performance data that buyers can review — not marketing claims. This isn’t a hobby project; it’s an operational product line designed to be serviceable, supportable, and worth the money.
Engineering Test Fleet
Active development and validation vehicles used for real-world testing, data collection, and platform validation.
Platform validation & systems testing
Legacy platform benchmarking
Engineering & validation platform
ELR platform validation vehicle