Battery disconnected Signal

[archie18]

I am working on a project, 160W smps with battery back-up. This customer needs a signal which indicates that battery is not connected. I was thinking of using battery charging current as sense for batt conection, but in case batt is or gets fully charged then no current will flow. How to sense that?:?
Can anyone suggest a circuit for charger in which a fault signal is to be generated when Battery is disconnected. Appreciate your inputs on this .

 

[chuckey]

I believe that there will always be a charging current albeit , a very small one- perhaps microamps. The very large batteries that are use in telephone exchanges where each cell is 1m X 1m X 1m the charging current is 50mA. Perhaps if you put a light load on the battery of 1mA, it would have no effect to speak of in its support time but would allow you to sense that 1mA. If you put a diode in series with the current charging path but sample the battery voltage at the battery end of it, a Si diode should drop >.4V across it at micro amps, but if the right diode is used with a 5A forward current would only drop .9V.
Frank

 

[Genomerics]

Won't be totally right given your converter will probably have some bulk capacitative output filtering but as a thought assuming you did have a fully charged battery on the output might you try, after the main converter has reached some low level of supply current, periodically shutting the main converter down and loading its output separately?

If there is a battery connected you would not expect a voltage drop/droop. If the battery is not there then you will get one and can flag it.

Genome.