In the above photo the size of the replacement, extended battery is shown next to the 3DS.
The Short Version: I purchased a 5000mAh Li-on Extended Battery for the Nintendo 3DS for about $20 via Amazon. It significantly increased the charge capacity of the device. I found the larger bulk of the entire system to be an acceptable trade-off for the extra play time this battery provides.
This week I decided it was time to replace the factory battery in my Nintendo 3DS. It wasn’t because it failed to maintain a charge but simply because it didn’t last as long as I would prefer. Now, I wasn’t draining the battery from playing games. In fact, most of the time I drained it simply by leaving it in stand-by but not on the charger. However, I also wanted to upgrade the battery because I thought I might begin playing the system more frequently and that it would be nice to not feel tethered to a power cable when I’m at home.
This time I chose a solution that I thought would be more elegant in its utility.
Late last week I purchased a Monoprice 5000mAh External Battery Pack. It includes two USB charging ports (one for 1 Amp devices and another for those that need 2.1 Amp) for output and can be recharged via a micro-USB port. The cost was reasonable at just under $30.
Now, I haven’t had any problems with the inexpensive cables I’ve purchased from Monoprice. However, the devices are often hit-and-miss. So far, this one seems to be a winner but having owned this item for less than a week isn’t enough time to really know yet.
The elegance of this package is that I can use it with almost any small device that can be charged via USB. Combined with a few UPS backups, a CPAP battery, and a solar battery at home I now have one more emergency power source in the event that I ever need it.
It also fits easily into my laptop bag. It’s not tiny. It’s larger than the iPhone but it does fit into a pocket well enough that one can connect the charging cable from the iPhone to the battery back and carry it around.
I’ve used it several times this week to keep my phone charged at times when I was using the phone more frequently than usual.
Updated 11/17/2012: This continues to be a good solution for charging my iPhone without having to use a wall charger or when one isn’t available. I’ve used it several times to charge other devices including a couple of different Android devices, my wife’s Sharp FX, and a mifi device.