Nimh CC charging circuit help

[sahko123]

Heyo everyone I wanted to see if anyone can find any particular faults with the following cc charging circuit. The boost converter will take 5v from a USB qi charger and boost it. The feedback is handled by a diff amp on a shunt resistor to allow for a cc charging current of 500mA which is about 0.25c for the battery. The next opamp uses a zener to prevent overvoltage by increasing the feedback voltage and reducing the boost voltage. With a diode to prevent reverse current going back into the boost converter. Diagram shown below.

Can anyone find any potential issues with the circuit as is? In terms of charging and overvoltage protection? Thanks in advance for any replies.

[Vovk_Z]

You can use old good LM317 for that with both CC and CV modes without any opamp. Look at datasheet (or application note) for a needed circuit. Just set step-up converter for needed voltage plus 3 VDC for LM317 additionally.