My read of the #6 schematic is that the battery is V1, and is connected to the monitor through M1 when V2 pulses high.

That's my take as well, but as you said when V1 is disconnected the output goes high and latches. That doesn't indicate the battery is low.
I believe that will be obvious to the TS when he constructs the circuit.
SG

 

The only way to prevent a battery-disconnect from generating a false fail-mode signal is to enable the fail-mode signal latch with the battery connect signal. For all of the circuits posted so far (#6, #17, #18), a disconnected battery and an under-voltage battery appear the same to the comparator/latch circuits.

#17 - Isn't the pin 4 voltage above 5 V in some conditions?

ak

 

a disconnected battery and an under-voltage battery appear the same to the comparator/latch circuits.

A disconnected battery will generate a false error signal in #6 and #17
SG

 

Second

Any idea about how can i implement this ?

SG