I haven't read all the posts but this is interesting. My analysis of the circuit: IC-7300 schematic: page 8 left-hand side https://www.hamradio.co.uk/userfiles/file/IC-7300_Schematic_Diagram.pdf Clock IC: RX-8803LC, typical current 0.75 uA, max 3.4 uA https://support.epson.biz/td/api/doc_check.php?dl=brief_RX-8803LC&lang=en Cell: ML414HIV01E, nominal 3.1-2.0 V, 1.05 mA-h to 2.0V (see graph), 72 recharge time at 30 uA https://media.digikey.com/PDF/Data Sheets/Seiko Instruments PDFs/ML414H_E.pdf Diode: L1SS400, 0.4v forward drop 1 uA, 20 nA reverse current https://html.alldatasheet.com/html-pdf/135337/LRC/L1SS400T1/118/2/L1SS400T1.html Resistor: 3.3 k ohms Notes (25 deg C = 77 deg F) The circuit cannot fully charge the battery. It can charge it to 2.9 volts which I estimate to be 80%. The circuit cannot overcharge the battery. The diode and 3.3 k resistor are used together to meet safety agency approval for single component failure with no battery leakage. The IC can discharge the battery to 1.6 V or lower. The diode reverse current does not significantly discharge the cell (it is 1/40 the typical clock IC current draw). The calculated operating time for max to typical IC current based on 80% charge is 240-1100 hours, or 1.4 to 7 weeks. My IC-7300 My IC-7300 was stored unpowered for 6 months and lost its clock setting. I reset the clock.