Have you tried to charge the battery for a long time: at last one night? Battery: 0.0 V. means it's completely empty.
The battery is an integral part of the unit's power circuitry -- without getting too technical, the power (even if from an external source) has to go through the battery in order to power the device. If the internal battery has failed (I.e. though an open or short circuit within it), or removed, then the receiver circuitry will not receive power because it cannot go through the battery.