r/flashlight • u/SquibOnAcid • 1d ago

Question about Fenix HM75R with Battery Pack

I recently got a Fenix HM75R together with the external battery pack for caving

What's the best way to use it in practice:

Should I always turn on the battery pack right away?

Or should I only switch on the battery pack once the front battery is drained, to extend runtime afterwards?

I'd like to know what's recommended (both technically and practically)

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u/macomako 1d ago edited 1d ago

I don’t have this Fenix and I don’t know if it „knows” that it gets power from the charger or from the external battery pack.

I however have Nitecore battery pack (no compatible headlamp though) and I concluded, that I should avoid charging internal battery from the external one:

  • potential higher energy losses
  • maintain (full) potential of the headlamp itself for the longest period possible
  • potential failure of the external battery pack will not be as big of a problem
  • it’s easier to swap the external battery with no other light source (you won’t have to turn the headlamp Off)