RCR123A vs. 18650 in LED lights

[coppertrail]

In reviewing the battery runtimes for several Lumapower lights, I have want to make sure I understand this correctly:

If (2) 3.6V RCR123A cells are used, it will draw 7.2V, resulting in increased brightness but less runtime.

If (1) 3.7V 18650 cell is used, it will draw 3.7V with lower brightness levels and increased runtimes.

The lights in question will accomodate both types of cells mentioned above.

 

[2xTrinity]

In reviewing the battery runtimes for several Lumapower lights, I have want to make sure I understand this correctly:

If (2) 3.6V RCR123A cells are used, it will draw 7.2V, resulting in increased brightness but less runtime.

If (1) 3.7V 18650 cell is used, it will draw 3.7V with lower brightness levels and increased runtimes.

The lights in question will accomodate both types of cells mentioned above.

Those Lumapower lights use Buck converters (voltage step-down only). With two cells, the battery intput voltage will always be higher than the output, so it will be able to maintain 100% brightness until the cell is essentially spent. With a single cell, when the battery is fresh (4.2V off the charger) the light will begin in regulation, but once the intput voltage drops below the output of 3.7, it will direct drive and gradually get dimmer. Due to the fact that 18650s have longer runtime, direct drive has no driver losses, and LEDs are more efficient when underdriven, the 18650 will run much much longer.