I did search and read a lot of varying opinions on this site, I'm just trying to get a straight answer.
I have an ordinary 3.8v Lithium cellphone battery. I have a USB charging cord for it, but I understand the typical USB 2.0 port puts out 5 volt.
EDIT: I am charging this battery in the phone. So the question should really be--what voltage limit from the input can the phone handle when charging its 3.8 volt battery? It seems fine with 5-volt USB or a 5-volt cube/transformer. What about 12 volt, or more? This is the crux of my question. The phone clearly has some form of regulation in it and I'm wondering what those limits are, in a general sense.
Quite simply--am I hurting the battery by charging it like this, or should I only charge it with a dedicated wall-charge that specifies 3.8 volt output? The Samsung cube I have --that I thought came with the phone--says 5v output. I could be wrong, this cube could be from another device.
So I guess my question is kind of answered because I've been charging like this for years and never blown up a battery--but I just got a new battery and I want it to last more than a year. It seems after a year I get to the point where a charge will only last about 12 hours of normal cellphone usage, whereas when they are new I can get two full days or more out of a charge.