ESU-2300 will not to turn on?

What would cause an ESU-2300 not to turn on?

The ESU-2300 contains a hardware safety circuit that is designed to protect the built in battery. If the battery voltage is too low the circuit will lock out any operation. The unit will not turn on. Some of the early models may not alert the operator and the unit will go into this mode. Newer versions of the software will give adequate warning.

To rectify this situation, plug the unit into the AC line adapter. The unit should then turn on. Leaving the adapter plugged in to charge the battery.