Our /2 Coffee Can Tail Light has been re-packaged to suit specifically 6-Volt or 12-volt systems.  Please follow these links:

6-Volt /2  Coffee Can Tail Light

12-Volt /2 Coffee Can Tail Light

The first generation of /2 Coffee Can Tail Lights was designed specifically for the original 6-volt systems.

By coincidence the upper maximum voltage limits of the circuitry were high enough that nothing would be electrically damaged if the units were installed in 12-volt systems, and many potential end users inquired if they might indeed use the light on 12-volt /2 conversions.

In response to these questions a thermal analysis was performed as the extra power of the 12-volt system would have to be cast off as heat.  The thermal analysis showed enough copper mass in the circuit board to permit 12-volt operation.

To test the thermal calculations a first generation tail light was placed in an industrial oven and tested for over 50 hours with both brake and tail light on at 140 degrees Fahrenheit.  The license plate light bulb was included so as to add to the heat load, and the chrome bezel was used to aid as a heat sink:

http://www.culayer.com/testing.htm

Customer feedback on the first generation tail lights indicated a desire for more brightness during braking.  In response, four more 10,000 mCD LEDs were added to the brake circuit to create a second generation taillight that had 12 LEDs for tail function and 16 LEDs for brake.  Well within current limitations, the additional 80 mA of current had a negligible effect at 6-volts.  At 12-volts however the tail light units ran even hotter due to the increase in power consumption.

In our current third generation of product, half of the 16 brake LEDs have been supplanted with 20,000 mCD LEDs whose current requirements can be as high as 50mA each (as opposed to 20 mA), for a total of 240mA more than its predecessors.

Although the brake system circuitry is only on for relatively short periods of time as compared to the tail light circuit which is always on, it was felt that the increased power a 12-Volt system imposes warranted a separate and unique circuit solution that would operate at reduced heat levels to help insure that the brake circuit voltage regulator would never shut down from thermal overload.