detecting backup battery connection to circuit

[canarybird33]

Hello
I need your help.
I designed a circuit to charge a 24v , 4.5Ah battery. Now I'm trying to detect if battery been removed from circuit.I have designed this circuit but it doesn't work because when I disconnect the battery , a voltage is over the node 'A' and my circuit detect it as a battery. How can I solve this problem?

As you can see in pic1 the battery is connected and in pic2 the battery is disconnected

 

[chuckey]

The input to U1b goes from 17.7 (no batt) to 16 with batt. Just reconfigure the circuit so the buzzer goes of with this change in voltage.
Frank

 

[canarybird33]

The input to U1b goes from 17.7 (no batt) to 16 with batt. Just reconfigure the circuit so the buzzer goes of with this change in voltage.
Frank

I'm afraid You are wrong. because 17.7 is a division of battery which is need.
you know this is my design which has no problem (new attachments) but previous attachment doesn't work properly because:
when battery been removed not only the voltage of Node 'A' (see post1) doesn't drop but also it goes up(because of LM317 is going to provide a voltage on Node 'A' to charge the battery)

I want to ask you How can I fix this problem?(when battery been removed voltage of Node 'a' must close to zero)