From their FAQ:
"...The unit is primarily intended to provide instant power for a cell phone. It is recommended as a battery extender. If your phone is on the last bar of battery power and you will be placing a call you should plug the unit into the phone and make your call while the unit is plugged in. During the call the unit will provide the power necessary to make the call without further depleting your battery. Using it in this manner will provide the power needed to make all the calls until you can charge your phone with your home charger or car charger...."
I'm no expert, but it seems to me that this is exactly the wrong way to use lithium cells. Isn't this exactly the same as mixing old and new lithium cells or "mis-matched" lithium cells ? The "new" cell trying to charge up the "old" cell is exactly what they say is the problem with these things. This is precisely the situation they tell you to avoid if you don't want a KABOOM. If I've got this wrong, please steer me in the right direction
edit: I hear kaboom is frowned upon, the preferred phrase is: "Rapid disassembly accompanied by flame."
interesting point. i'm not sure that it really works that way though.
first, an excerpt from the source you quoted:
"During the call the unit will provide the power necessary to make the call without further depleting your battery. Using it in this manner will provide the power needed to make all the calls until you can charge your phone with your home charger or car charger...."
notice that, according to the quote,
"the unit provices power...to make the call", and further "you can charge your phone with your home charger or car charger"
NOTHING is mentioned of charging the battery with the unit in that quote. Maybe it does; maybe it doesn't. Don't want to make any assumption here from lack of evidence. The only thing we can conclude, assuming that the statements as stated are accurate, is that the unit can power the phone to make the call without resulting in further battery depletion, and that you can use your home or car charger(s) to recharge your battery. Any other conclusions might be deemed non sequiters, IMO.
Now, however, let's assume, for the moment that a unit can be used to recharge the phone's battery.
Would the unit be directly charging the battery? Or, would the unit be powering some electronics in the phone which isolate the unit from the battery directly and which in turn then charge the battery (meaning, the electronics in the phone then directly charge the battery)?
don't know, but that's how it might work *IF* the unit has any ability to charge the phone's battery. just a thought.