So I had a rechargeable Nomad battery pack laying around. Which of course no longer works. :
Now unfortunately my puppy ate my 8gb memory stick so I lost a few pics.
First thing you need to do is open it up. You can use a credit card. Just slide it in between the two halves and they will pop apart.
Then you need to remove everything that is in it. It has 6 batteries , a protection circuit, and a charging jack. Leave the two power wires (green and orange). They will be attached to the new battery.
After everything is removed you will need to make room for the new battery by clipping off some of the plastic in just the bottom half.
It will now look like this :
The battery you will want to use is a Sony np-f550 2000 mA battery. You can get the battery and charger for around $15 shipped on Ebay :
http://cgi.ebay.com/Battery-NP-F550-F33 ... 19b7a016c5

Now I used a type M female power adapter for the charging jack. I got it out of a Retro-Duo I had laying around. You will have to file out the spot where the old charging jack was for the new one to fit.
You will need to solder the orange wire to the positive side of the battery. Then wire the positive side of the battery to the positive prong on the charging adapter jack.
Then wire the green wire to the negative side of the battery. Then wire the negative side of the battery to the negative prong on the charging adapter jack.
Then I used a type M male power adapter from Radio Shack. I opened the charger and soldered in the power wire and then wired it to the male adapter.
One advantage of this is that it will last around 5 1/2 hours with a stock Nomad. With a Nomad that ha a new screen like mine in it , it will last around 8 1/2 hours.
Plus it is a LOT lighter than with the stock Nomad battery pack.