The Charger operates in a constant voltage/current mode.  
It  is designed  to  have a  square type of characteristic as illustrated.  When  the  battery is low, the charger is under
the  control  of the current feedback signal, thus ensuring that  a  constant  current is applied  to the battery.   Under 
these  conditions the  battery voltage will rise slowly untilthe  predetermined  constant  voltage  setting  is reached. At  this point  the charger current  will decrease while  the charger operates...