Lead car battery capacitance

A lead car battery condition is observed by measuring the voltage between opened terminals, though the datum obtained by opened voltage measuring is abstract compared with the method of doing the specified gravity of electrolyte. Just measuring voltage method is simply easier than the latter one. The battery shown here was self-discharged until loosing the electric capacity that could not activate starter motor of Hybrid TOYOTA Crown, 65D23L. For 9 hours gradual charging at 16,5V/2A(switching power supply) has recovered to show 12,20V between opened terminals, almost 50% capacitance has saved and more charging is required to fulfill the original capacitance. Basically, the battery once ruined would not recover the original performance, but it would play a part of emergency use. As a common sense, a lead battery should be charged at 10% higher voltage with 1/10 current of the battery capacitance, I make it a rule to at much higher voltage with lower current taking longer time as gradual charging method, according to my experience, this method has never caused any problem like destructive curvature of electrodes. Before all, electrode liquid level should be at the same decided amount by adding pure water promptly.
For a long time of period I believed that the play of a lead car battery is just activation of starter electric motor and give an initial combustion spark, then once started, the battery has almost nothing to do with the motor performance, because the power supply is mainly by the alternator rotating together with motor performance. But, actually the fact isn't true, because some ruined battery requires charging energy from the alternator connected with the motor by way of belt and the motor power would be consumed by activated alternator rotation. This is why a new and healthy enough car lead battery provides light and comfortable run. As the charging energy in an alternator is supplied by motor combustion energy, so a fully charged requiring no charging is one of an indispensable factor to establish comfortable and astringent run.