A quickly failed experiment

I believe it has been posted that you could put just 4 AA lithium batteries (as opposed to 8) in a PT Surge and it should be OK as the higher voltage should be compromised as you don't have another battery set in parallel. Well I tried it and the light bulb blew instantly after a split second of intense light.

I wish someone could come up with a suitable Surge bulb that worked with NIMH rechargeables. When I use my Surge with NIMH's, the light output is steady but noticeably dimmer then with fresh alkalines. When I use alkalines, the initial brightness is good but dims steadily throughout the battery drain.

So in other words, you want your cake and eat it too?
If you're electronically minded, you could shunt a small resistor between the battery contact and the lamp - I wouldn't know what value, just to bleed off some of that Li voltage, say down to 1.55V (not under load) would be about ideal.

Or get a Willie Hunt LVR. (not very cheap, and size might be a problem)

Efficiency, and max-output without blowing the bulb in an instant. And you can re-qure the batteries to full-series, and get really long max-brightness (lithiums should handle the current... or NiMH.)