Q5 drop-in primary/rechargeable help

[Lost Time]

I'm hoping somebody can tell me what this means:

I've got a Solarforce (ebay generic) p-60 drop-in sitting inside a Brinkmann Maxfire LX host. I've been running it with two cr123 primaries and wanted to see how it would run on li-ion. I tried out a new AW 17670 I just received,which was showing 3.8v before I put it in. The light is noticebly brighter on the primaries. The drop-in is advertised to run 3v-9v, but it doesn't specify if it's direct-drive, regulated, etc.

What can be deduced, if anything, by the relatively weaker light I'm getting from the li-ion battery?

 

[mdocod]

that it probably will make light between 3.0 and 9.0V, but that it is only a buck style regulator and drops out of regulation ~0.1V above the Vf of the LED like many buck style regulators, so below ~3.9Vbatt you are probably out of regulation.