Battery charging algorithm

[--BawA--]

i am designing a lead acid battery charger using pic16f mcu.The charger incorporate 3 stage charging algorithm. i have one confusion that should i continuosly monitor the battery voltage and current or should i monitor the battery voltage and current during OFF cycle of PWM?

 

[iop95]

Current must be monitored in ON cycle and I think best way is to include at each 1-2 minute a long OFF (few seconds stop charging) to measure voltage. If measure voltage in charging is not correct, this value is not no-load battery.