Is this current limiting circuit usable?
Is the pulse waveform at pin 6 of the UC3842 as shown in the picture normal or acceptable?

 

I think you are charging a 12V battery from a 18V power source.
It looks like there is no "max voltage" function. Full charge. By looking at the voltage across V2 you could stop/reduce the charging current when the voltage is too high.
As the V2 voltage get high you might hit the max duty cycle of the IC. This will limit the full charge voltage.
Current is measured by R6, which is the MOSFET current. (Average current 3.24A?)

Is this how it works?

 

I think you are charging a 12V battery from a 18V power source.
It looks like there is no "max voltage" function. Full charge. By looking at the voltage across V2 you could stop/reduce the charging current when the voltage is too high.
As the V2 voltage get high you might hit the max duty cycle of the IC. This will limit the full charge voltage.
Current is measured by R6, which is the MOSFET current. (Average current 3.24A?)

Is this how it works?

I am designing a battery charger ranging from 11.8V to 14.4V. The DC current through MOSFET Q1 is 3.24A. In practice, the actual battery voltage can be higher, for example, 12.8V.
So can my circuit be used? The 14.4V charge cutoff feature will be designed later.
My current circuit is just for testing whether the principle is correct.