ICOM IC-7300 Replacement Battery Internal Clock. ML414H-IV01E ML414H
The clock always set to 0:00 when the radio had been off??
The Icom IC-7300 has an internal rechargeable battery to keep the running of the Clock. The battery charges when connected to your power supply, however drains when left un-powered for a while. The issue seems to be that this Lithium Ion battery has a limited number of deep cycles and will eventually no longer be able to hold enough charge to keep the clock running.
This is the replacement part you need.
WARNING if you are not experienced in SMD soldering or using a soldering iron in a very FRAGILE environment – do not try to perform this fix yourself.