I have a Luxos U which I believe uses similar circuitry. This website (a google translation) indicates that the Luxos U uses the same battery pack as the Werk:
https://translate.google.com/transla...00271,15700301

On my Luxos U there is a little red light on the remote switch that indicates if there is adequate charge in the pass through cache battery to charge a device through the USB port.

I have often noticed that the red light goes off and on when charging things, and I have come to the conclusion that when I am draining the cache battery (drawing more power out of the cache battery than replenishment rate), that eventually the red light goes out and the charge stops for a while and then it starts charging again later. I do not know if this is true or not, but that is the general assumption I have made.

If I am right, maybe a new battery pack would solve your problem? It is my understanding that Peter White sells them, but I do not know the price.

But, you said you got no power out of it during a three day trip, that suggests a problem more severe than batteries, so my guess on batteries could easily be wrong too.

My Luxos U battery pack is still functional so I have no desire to start playing around, but I noticed this other posting some time back and noted it in case I need to buy some batteries from an alternative source.
Luxos U not showing red cache light & not charging


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I tour with a Sinewave Revolution and an external pass through cache battery, the battery pack was designed and sold for solar power systems, so I can't advise further since I do not tour with my Luxos U.

Good luck.