Thursday, December 6, 2012

Replacing an iPod Battery

...the fun way. This adventure began a week or two ago when i washed my iPod Touch 1st Generation because I had to wash the load twice for reasons i will not say, haha. After throwing it in a bag of rice for a few days and putting some mild heat on it (evaporate the water), i got all of the water spot out of the LCD and it seemed to be dry. When i plugged it in everything worked but the WIFI. The next morning i followed my usual routine of using it with my radio mod to play music in the car. No supervised here. Once i got to school the iPod was at 20%, yikes! I figured that the water shorted the battery and ran it down too low, just like i did accidentally to one of my LiPos (did short the lipo, though :)).

A Temporary fix
For a while i just left it plugged into the car charger, but then i could hear the the engine whine in the audio because of the ground loop. this loop is caused by having the ground of the charger connected to the iPod and the ground from the radio in the audio jack. basically, its just two grounds hooked up to the same iPod. The people with those fancy speaker systems in their cars also have this issue.

Take the Back cover off
Since i cracked it open already for drying out, it was pretty easy to open up again. just take a x-acto that has a perpendicular blade (relative to the handle):
1. Get it between the little joint back case (silver) and front plate (black) on the side of the iPod.
2. Twist the knife and get it under the silver case just a bit (1/8in or less).  You should hear a little pop of the
3. Do the same all the way around (leave the dock area for last).

It is possible to damage something like this, but as long as you don't stick the knife in there to far, you wont hit anything. This area only has the battery, WiFi assembly, and the lock button exposed. that is the reason why i said 1/8in or less earlier. Everything else is under neath or covered with a metal plate.

Get the Battery Out!
After getting it open the first time i had to pull out the battery. I started out by cutting the individual wires to the battery (wouldn't want to short the + and - with a metal wire cutter). Then i carefully tried to cut the stick pads that hold the battery down with a long bladed x-acto. Did i mention try? I managed to cut open the battery: oops. If this were a lipo it probably would have went up in flames, but Li-ions are more stable and only gave off the sweet-ish lithium style lipo smell. If you smell this get it off there quick and throw it in something like sand.

Where to Get a Replacement
Then i needed a battery replacement. I could get a 6$one from ebay, but since i wanted this to be 100% DIY, i found a different battery source: flip phone batteries as these all have nearly the same style of battery If you find the right ones you can fit two of these 800mah Li-ions side by side and get 1.6 times more mah  than a regular 1000mah iPod battery. If you're lucky you could find a smartphone battery that will fit! With these phone batteries you must consider three things:

Contact pads on the battery. 
A regular phone battery has three contacts just like the iPod does. They are:
    IPod          Phone             Meaning 
1. Black             -             Negitive, GND
2. Red               +             Positiive voltage, 3.7v nominal (like a 1s LiPo)
3. White        -none-         Charging lead

The charging lead (ill call it 'c') is there to reduce the stress on the battery while charging and using the phone/ iPod at the same time. On phone batteries it is commonly the center contact and will measure the same voltage as GND to positive. See the picture below for what i mean:
Extra padding
Also in the image above you can see all of the plastic and the sticker on the actual battery. i easoly pulled it off and has a lower profile battery.

The Health of the Battery
If you are paralleling two batteries you want to make sure they are the exact same model, have a similar age and are charged to the same voltage. If you have a big voltage difference, you could end up killing a battery as the batteries would attempt to stabilize (as air pressure goes from high to low to stabilize, yeah, go AP Physics)  This would result in a large amount of current flowing that could exceed the c rate of the battery and damage it and also damage the battery that the current is flowing to. Just keep the voltages similar ;)

The Action!
Next i rigged up the new batteries to the iPod.  This was as simple as connecting the batteries in PARALLEL which keeps the same voltage, but adds the mah of the two batteries, in layman's terms. This is done for all contacts pos, neg, and c. I did this with some thinner stranded wire as it doesn't need to carry much current. I pretty much followed this:
1. Solder positive battery 1 to positive battery 2
2. Solder negative to negative
3. Solder C to C
4. Solder negative form battery 1 to the negative pad on the iPod PCB
5. Solder C from battery 1 to White (C) on the iPod PCB
6. Solder positive from battery 1 to the positive pad on the iPod PCB

Finally! Testing Time!
I pressed the button and it worked! Yay! Also, must note that from looking at a possible donor iPod Touch 2nd Generation, that flip phone batteries probably wont work because of the slimmer design.

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