[Samsung Galaxy Nexus] ttabbal:
I was asked for more information after mentioning this in another thread. I felt like it might generate some questions, so it should have it's own thread.

I wanted more power, but the cheap extended batteries are, well, cheap. :D

They are OK for the price I suppose, but they lose power quickly and in many cases aren't any better than the stock battery. I wanted a real increase as well, the 2000 from Samsung wasn't going to cut it. So, what to do? Connect 2 OEM standard batteries together! :eek:

Materials:

An extended battery back cover from a cheap ebay battery or a friend, etc. The stock Samsung "extended" back cover from the 2000 won't work. I used the one from a Hyperion "3500".

2 OEM 1750mAh batteries (shimshop on ebay has the real deal, about $30/per)

Soldering skill and equipment.

Directions:

Remove the sticker covering the battery. It peels off without too much hassle. You will be left with a bare battery with the NFC antenna on one side. I've attached some images so you can see what they look like taken apart.

Remove the plastic cover on the side with the holes for the battery to connect to the phone.

Now you have a circuit board that is kind of a pain to work with. Both ends you can get to are (+) terminals, as is the metal case of the battery. The (-) terminal is in the center of the battery, see the little hole in the center of the PCB, that's your other terminal. How to connect? Well... There are a couple options. Here's what I did.

Peel up the NFC antenna and let it hang there.

Use a Dremel with a cut-off wheel to cut through the metal connections from the battery to the PCB on the small ends of the PCB.

GENTLY lift the PCB up a little so you can get under there.

On one battery, remove the PCB entirely. Just wiggle it back and forth a bit or use wire cutters to disconnect the (-) terminal. The metal tabs break off EASY. Peel up the NFC sticker as well and just put that bit aside.

Put the second battery over the first. Secure with a bit of tape or something to make soldering easier.

Solder a piece of wire between the two (-) terminals. It doesn't have to be huge. 18ga should be plenty. It's short and likely won't ever see more than about 1A. NOTE: As I mentioned the ENTIRE METAL CASE of the battery is (+). If you short this wire to the metal case, it will get VERY HOT, VERY QUICKLY. DON'T DO THAT. It's bad for the battery, and for you.

Hopefully, you didn't break the (-) terminal off the second battery on the previous step.

Now gently press the PCB back into place on the lower battery. You might have to use a knife to cut some of the plastic between the PCB and the battery to make room for the little wire.

Line it up carefully, as close as you can with both sides and tape it down. Now solder a short wire between both (+) terminals on the battery. You can use the wire and solder to bridge the gap to the PCB from cutting it off before. :D

Now you have this NFC antenna in the way. Use a small piece of the sticker as insulation under the top 1/2" or so of the antenna on the back. Just to make certain that nothing will short to it. (I don't think it will, but it's cheap insurance) And set the NFC antenna on the new back of the battery. It won't fit quite right, and will overhang a bit. That's what the sticker is for. You could try to extend the connection, but it's more trouble than it's worth.

Remove your earlier tape holding things together.

Use the two stickers you removed from the batteries to cover them back up, sticking the NFC antenna down in the process. Well, most of it anyway.

Now you can try to cut down the tabs on the top plastic to fit properly so you can put it back on.. but I didn't bother. Once I made enough space, it got really flimsy and broke easily.

Now test the connections on the PCB with a voltmeter. Make sure you don't have polarity wrong or anything. Pretty hard to do, but you're going to put it in a $500 phone, so watch it. :p

If it looks good, put it in the phone and power up. It should work fine. Put the back cover on, and maybe get a case. I'm using the cheap bumper case from ebay. It leaves the back exposed, so just about any battery will fit. It looks a little ghetto before the cover, but it works fine. And it's made from OEM cells, they even have "Samsung" and part numbers laser etched into the metal body. So it will perform to spec, tested with a meter, last as long as a stock battery, which should be a couple years, and if you aren't completely stupid with a soldering iron, be as safe as a stock battery.