This does nto apply to starting batteries as much as house.
To recharge house batteries from 50% with the proper (30% C/20) converter/charger takes something like six hours
Even with starting batteries you get to 90% very fast but that last 10 takes a while.
Also monitor system voltage. THat just got easier for me as I have a new toy and all I need do is tickle the touch screen a bit and wher eit now sayd 15:25 (That's the current timer in Greenwhich England or Cordornated Universal Time as it is now called) it will change to xx.y volts.