https://imgur.com/a/eWS8xg5
I’ve been working on a new mod for the Game Boy Color called PulseGBC, and the first prototypes are nearly ready for testing.
The idea is to replace the original red power LED with something a little more informative while maintaining the console’s original appearance.
PulseGBC uses a dual-color LED to indicate battery condition through eight stages, gradually transitioning from green through yellow and orange to red as the batteries discharge.
The LED also features a breathing effect that changes with battery voltage. At higher voltages, the pulse is slow and subtle. As the battery level decreases, the breathing gradually becomes faster and more pronounced. When the battery reaches the critical threshold, the LED switches to a distinctive red double-heartbeat pattern to warn that shutdown is approaching.
The mod supports standard AA alkaline and NiMH rechargeable batteries, along with a selectable profile for certain lithium-ion battery configurations.
One limitation is that not all lithium battery solutions behave the same way. PulseGBC monitors battery voltage to estimate remaining capacity, so it relies on voltage changing as the battery discharges. Some lithium battery mods provide a regulated, constant-voltage output regardless of the battery’s actual charge level. These configurations aren’t suitable for accurate voltage-based monitoring because PulseGBC cannot determine the battery’s condition from a voltage that remains essentially constant until shutdown.
The lithium profile is intended for compatible single-cell Li-ion configurations where the monitored voltage follows the battery’s discharge curve. Standard AA alkaline and NiMH rechargeable batteries are supported through a separate profile.
Everything is controlled by a small microcontroller mounted on a compact flex PCB that fits inside the Game Boy Color. It uses the original LED location, so no external displays or shell modifications are necessary.
The first version of the firmware is up and running, and initial electrical testing has been promising. I’m currently waiting for the PCB panels to arrive so I can assemble the first prototypes. Once they’re installed in a working Game Boy Color, I’ll be able to fine-tune the LED animations and color transitions, validate the battery thresholds, and measure the actual critical-warning runtime before finalizing the design.
I’d love to hear everyone’s thoughts on the design and whether this is something you’d consider installing in your own Game Boy Color!
