The solar panel actually charges a 4 pack of batteries. that four pack of batteries is used to charge the phone. other than that is just a general battery charger.

the GPS uses 3x AA
the head lamp uses 4x AA
The SPOT uses 3x AAA (That the solar charger can also carry)
Goal Zero Guide 10 Plus (used to charge the phone) 4x AA

Normally when I trek out (winter or summer) I carry a 100% extra load of batteries. So if I carried enough batteries for everything I would have 25 oz of batteries

I should explain that i do a lot of deep woods winter trips where the sun is not up long, and the time from danger to death is short.

Im on the fence as to if I should carry half the weight and be limited to what i bring or have the ability to charge over and over? Also with this setup I can take care of other people in my group with head lamp batteries, phone charging. and in return I can off load some weight on them.

As for the charging of the panel. by using the 4x AA in the Guide 10 Plus it allows the panel to charge in low light conditions.. just not as fast. Also I like to hike heavy into a spot then trek out in different directions. So i could leave the panel out to charge a set and stay light for my different trips.

It wouldn't be horrible is things died... the GPS, sad yes but I've never had a situation where the GPS has saved my life... made things easier for sure but never saved me. However, this could change this winter as Im getting more into cold camping. Here in Colorado at 10,000' storms come in quick and having a gps to keep me heading in the right direction could be a life saver. The spot really doesn't even need an extra pack of batteries as it only comes on to transmit a message or send an SOS then goes off. its not a constant ON type device. The phone sits in standby 90% of the time, unless I see a picture or want to reference something I see. but I would notice if it did die and not being able to take some pictures would just be disappointing but not trip ending.

You make valid points and I appreciate them! I often think things over 100's of times