How to solder the 4-pin battery connector back to phone's motherboard?

Question

One wickedly hot day the battery of my old Nexus 4 swelled up. I use that phone as Android development platform, so most of the time it was plugged into the computer for USB debugging. It's been like that over a year without incidents, but this day it cooked the battery.

I ordered an OEM replacement, got excited seeing it is quite fresh, and popped the "trunk":

"What can be easier?" - i said. But i didn't know what was ahead..

1. Unscrewed 2 tiny Phillips bolts on the connector's metal top plate (marked with "V").
2. Had to apply some pressure to pop the connector up from the motherboard. I used one of the plastic hook-tools conveniently included with the new battery. Didn't know about the 2 side hooks (Phillips bolts weren't enough?!); but even if i did - everything is so tiny and hard to get to..
3. Original battery was glued to the case, but not permanently. So again carefully i pried it off with another flat plastic tool.

All seemed wonderful, i was about to put the new battery in, when i noticed that its connector looks different.. Huh?? That's when i saw that 3 pins and the connector's piece, which was soldered (not too strongly) to the motherboard, got ripped off of it, leaving one pin on the mobo (i took that photo not yet realizing what happened):

Now after studying the difference between battery connectors, i figured what happened and took the mobo's piece off the batt's one. Then while trying to fit it in place the 4th pin got unsoldered from the mobo too..

Here's what i have now: the plastic piece is intact with all 4 pins.

I'm gonna try to just attach it and see if 2 Phillips bolts make enough pressure to make contact for the 4 pins to touch the mobo. I can certainly superglue it back..

But i'd like a solution which is more robust electrically.

Is there a way to solder it back? Please, help!

Answer 1

It's hard to say, if you ripped up the pads (which looks like one of them is ripped up) then you'll have a problem. The copper needs to be continuous (especially in high amperage connections). This is even with soldering.

Is there a way to solder it back?

First off the connection must be soldered. Secondly, you must create a low resistive pathway that can handle the current, this can be done by blue wiring. If you don't know how to calculate the current or blue wire, then find someone who does.

Blue wiring involves soldering directly to the pad of the connector, then finding where the trace goes (if you have room) and either peeling back the solder mask, and/or soldering to another component on the same trace. This may not be easy on a device with limited space.

I'm gonna try to just attach it and see if 2 Phillips bolts make enough pressure to make contact for the 4 pins to touch the mobo. I can certainly superglue it back.

This will most likely result in failure, with modern phones, charging can use amps of current. If a proper connection isn't made, the battery will either not charge, or will heat up a resistive connection (think fire/melting).