ThankYou J Walking - and it seems to cover all needed information...been reading and rereading it over the last few. I've never considered a phone's operating system in terms of energy usage( kinda assumed they all used about the same)- and of course I own a new phone- the type that's not energy friendly. so it's going to be a powerbrick ( oddly no information on amazon as the actual weight of any of these rechargeable batteries) and I can't quite trust a solar charger- having no practical experience with one..... no action is going to be taken, until I return home in a few days, and can do some actual weighing of the old and new kit. but as it stands now it looks like, the proposed set up will be more that what I've been carrying. assuming I'll still carry map and compass. kinda a bit disappointed about that, but might try it on a section, just to see if it's as wonderful as I imagine.