Portable Power 8800mA External Rechargeable Battery Pack for 3DS

Portable Power is compatible with Nintendo 3DS
Designed for the times when you need instant power for your 3DS game device
Keep connected to your 3DS device and charge and play at the same time
High-capacity, rechargeable Lithium-ion battery pack for increased energy efficiency
Capacity of 8800mAh
Input: DC 4.6V 1.5A
Output: DC 4.6V 8800mAh

NDSi relevant product information

NDS vs. NDS lite vs. NDSi
The NDSi  has a brighter and more vibrant colors. Screen is also a little bigger.
In terms of size, there isn't much difference between the DS Lite and the DSi, but when you compare weight, the DSi is a considerable amount lighter than the Lite. For those of you who own a PS3, the difference is basically like the difference in holding a SixAxis and a Dual Shock 3. Speaking of controls, the DSi's D-Pad is considerably better than the Lite's.
The DSi now allows for downloadable software, includes 2 cameras for taking pictures, and allows for saving of voice recordings using the system's mic. All of the above can be saved to the DSi's internal memory or SD via the new port.
One of the biggest changes to the DSi is the inclusion of two low res cameras. These cameras have provided for quite a bit of confusion since the system was announced, so let us clear the air.
1. Both cameras are low res.
2. They are low res so they can easily be used in applications.
3. There is no flash on either camera, but there is compensation for darkness, much like any medium quality web cam. This also means that the video feed gets choppier and is more susceptible to blur in low light situations.