There are a number of ways to run a JeeNode off batteries. The lower bound is around 3.5 .. 3.6 V, depending on current draw. With 3.5V, the voltage regulator only has about 0.2V to work with, which is probably ok as long as the total current consumption stays under 50 mA or so. The maximum allowed voltage is around 13V, but drawing too much current at that level will lead to excessive heating and cause the voltage regulator to shut down.
So with alkaline and NiMH, you need only 3 cells.
For temporary connections, use the FTDI connector:
For more permanent connections to the JeeNode v3, you can hook up a 3-or-more-cell battery pack as follows:
The 10 µF capacitor next to the battery connectors can then be folded flat over these wires again, if needed.
Another option would be a 9V battery:
Keep in mind that 60% of those 9V will be turned into useless heat in the voltage regulator…
And then, there is the option of using a rechargeable Lithium cell (LiPo). They supply 3.7 .. 4.1 V – a perfect match, if you take the proper safety precautions with charging them.
Update – note that the FTDI connector and battery connectors are both attached to the same “PWR” line, so please remove the battery (or add a disconnect switch) when connecting the unit to FTDI.