Paul C. Buff, Inc. Technical Forum

I just unpacked and plugged in my Vagabond II pack and it hisses/whistles while it is plugged in and charging. Is this normal? Or should it be silent while it is charging? Any other sound quirks that I should be ready/prepared for?

It is normal for teh VII to "hiss" while charging. As the charge becomes more complete, the sound will dissipate. If you run it under a heavy load, you may also hear the sound. Be sure to keep the unit fully charged. If it is used and left to sit, the battery will sulfate and will result in a lower maximum capacity. Also, even if fully charged, then left to sit for months, the battery will self discharge (all batteries do) and will also sulfate unless a charge is maintained.