Deve, the fact that the battery reads 12.5 volts before starting and 13.5 volts after starting tells you the charging system is working, the fact that the voltmeter doesn't show 14.5V tells you the battery is pretty well fully charged and the charge regulation is working .... if you want to monitor the charging system in milliamps, go digital and get a lab quality ammeter .... the fact that an "almost totally dead battery" can still read 12.4 volts doesn't say anything about the condition of the charging system unless the engine is running, in which case a reading of 12.4V means it's not being charged - an ammeter reading "charge" doesn't tell you the battery is almost dead either [or has a bad cell], but a voltmeter reading 15-16V says it's time to load test the battery and/or check the charging system regulator function
Bill
