Dead phone, not sure why

[adesva]

S II i9100 running on stock with replaced battery (1900 mAh).

Problems started a day or two ago: battery was nearly empty and I connected phone to the charger. Noticed the next morning that the phone was dead and didn't react to the charger. Let a friend charge up the battery to 3.5 V or so, then put it back in the phone. Phone started working again. I then put the charger in overnight and it charged just fine. In the morning the phone was working when I disconnected it from the charger, but abt 20 minutes later the phone was completely dead.

Tried putting my battery in another i9100 and it worked just fine, his battery didn't help my phone.

Warranty has expired (and it's been rooted in the past anyway).

Any ideas on what to try or just ideas on what's wrong with it? I figure that if it was the motherboard it shouldn't have started working again y/d.

 

[SpookDroid]

Dumb question, but have you tried turning your phone on with the charger? Of course, you'd need the battery inserted.

It could be a damaged pin or something on the battery terminals, but it could also be a faulty USB port (it's fairly cheap to replace); on a friend's S2 he had a similar problem with his battery not charging and it was the USB port. Mine suddenly decided to randomly summon S-Voice on it's own and going into Driving Mode for no apparent reason; changed the USB port and voil?!, no more random S-Voice.

 

[adesva]

Dumb question, but have you tried turning your phone on with the charger? Of course, you'd need the battery inserted.

It could be a damaged pin or something on the battery terminals, but it could also be a faulty USB port (it's fairly cheap to replace); on a friend's S2 he had a similar problem with his battery not charging and it was the USB port. Mine suddenly decided to randomly summon S-Voice on it's own and going into Driving Mode for no apparent reason; changed the USB port and voil?!, no more random S-Voice.

No such thing as dumb questions, haven't you heard? ;p
Yep, tried it to no avail.

My first thought (after having the friend charge up the battery in some mysterious way) was that the port was faulty, but once it was charged to 80% or something, the charger worked just fine. The battery is a bit bloated, but since it worked in another phone while his battery didn't help my phone, we should be able to exclude that one as well. Which leaves us with solely the phone.

Thought it might be a hard brick, but shouldn't it react to the charger and/or boot up to warning triangle then? Either way I did nothing special to the phone prior to the crash(es).

 

[SpookDroid]

Yup, it might be the port or the power terminals. In any case, your best bet is to open it up and check for continuity between the power port, battery terminals, and power input to the mother board.

Or, if you have a Multimeter and a steady hand with very tiny cables, you could try doing a loop test on the power port. If the loop between the + and Ground terminal of the USB port fails, at least you know that something inside is cut off.

 

[developer1990]

From my own experience with batteries (have 6 of them and used them for more than one year...charging in external USB-device, and use them one after the other)...suddenly they phone will not boot even when the battieries are full...

My resoultion was just a bunch of new batteries....