JBD, the N900 may need a modified charging cable with the data leads shorted if your battery pod doesnt negotiate a charging rate.
Easiest way to do this is to split the outer insulation on a USB cable and use a soldering iron to short the green and white wires together with while carefully leaving the red and black power wires alone. You can seal it up with some shrink tube.
http://en.wikipedia.org/wiki/USB_cable
The E-werk is great for charging a smartphone once you get past the N900 requiring a smart charger to accept power.