NSB-25 uses six Li-Po batteries as an internal power source.
These batteries are connected in parallel for maximum efficiency and fail prevention.
NSB-25 may draws power from these internal batteries even if it is connected to the external power.
That can happen if,
1) External power supply capacity is insufficient.
2) External power is unstable. (Like car charger during the driving)

Using with any of that unstable power supply makes no problem on the copy/verify/preview operation of NSB-25 because internal battery power system supplements the insufficient portion.

But we got to know some times the sudden power spike of external power(induced by steering the power handle during the car driving) makes current spike from the battery happens.
If this current spike from the battery is too large, the protection circuit of the battery electrically disconnects that battery from the circuit.
That means the count of parallel connected battery reduced from six to downward.
So making users feeling battery does not hold charge.

This situation cannot be recovered automatically.
Only manual unplugging & plugging the connector makes disabled battery working back again.

So if you feel your battery working time became too short, try disconnecting and connecting the internal battery cable from NSB-25 and check if it is working.

See here to know how you can connect/disconnect the battery cable.
http://www.nextodi.com/support/view.php?bbs=en_download&id=164