Problem with "automatic" high/low flashlight mode...

[MyHeadHz]

I just bought a Coast PX1 (on sale at a local store).  I bought it to use with my rechargeable AAA batteries.  It works with the batteries, but it will only go into "low" mode.  There is no manual way to adjust high/low.  There is one button that somehow decides what mode to go in to.  With regular (not rechargeable) AAA batteries it generally toggles back and forth between the low and high modes.  There is no manual (online or with the light) that explains when or why it chooses low or high modes.  :/

I'm guessing there is some sort of voltage meter that only allows it to go into high mode if it has over a certain voltage... but that makes rechargeable useless as they generally run at 1.2v instead of 1.5v.

Any ideas on how to force it into "high" mode?  or am I probably screwed?

edit: title originally said "auromatic" instead of automatic

[kalel]

Some type of joule thief for batteries? No, there's probably not enough place to stuff a step up module in there, plus it might cause undesired operation.

There are some specific rechargeable batteries with zn that have a higher voltage, 1.6v (and more when charged up), but then there's the risk of having too much voltage and causing something to overheat. There might be other technologies that provide 1.5 in the desired package.

Other than this, if there's an internal MCU that chooses the modes (and toggles between them) I'm not sure there's much that can be done.

It does sound like when the battery is low (probably low voltage like you mentioned), the lamp doesn't want to go into high mode. It likely considers the battery to be low at the voltage of the rechargeable batteries.

[MyHeadHz]

Rechargeable batteries I've had in the past charged to 1.2v.  I decided to test these and they charge to 1.4v.  Well, two of them did.  The third cell was dead!  No wonder I had issues...

I replaced that dead cell and the light functions normally now with my rechargeable batteries.  After 5+ years, seven out of eight cells I originally bought are still good.

Sorry for the wild goose chase

[kalel]

Good that you solved the problem, it would have been annoying to get a moderately priced flashlight just to find out you can't use it without wasting batteries.