Fenix HP25, is it possible to use 2 18650 instead of 4AA!?

HI, I'm new here so please be gently with me

Anyway, I'm going to replace the headlamp on my caving helmet and after some research I found the HP25 as the pretty good choice mainly because the very good quality/price ratio but....

The 'problem' is that it uses 4 AA batteries while I prefer the 1865 pack like on the Fenix HP40F so I would like to know is it possible to use this battery pack from HP40F on HP25. I know it would be easier to get HP40F but it is not an option because the blue light source.

So to sum up is it possible to use 2 18650 instead of 4AA and if it is OK is it possible to get this battery pack from HP40F separately or do you maybe suggest some different 18650 based battery pack with decent capacity to use with!?The only requirement is to be water resist because I'll mainly use it in caves...

Thanks in advance and sorry about my English, it is not even my 2nd​ but 3rd​ language.

Teo

No, you can't use the 18650. You can get rechargeable AA, such as Eneloop batteries. There is a forum here all about caving headlsmps. Just search 'caving'.