I am designing a circuit using an ATtiny13V. The circuit will be in aplastic box that will be installed and located in a non accesible place.
There is a very long life non recargable battery inside used as back up power supplier. The whole circuit will be supplied by the mains power supply via a DC circuit. An ATmega88 always check the main supply connections from 10 points. It is very critical for the system not to stop even for a second transmiting the data.
There is a need for the system to know as soon as possible where the problem was each time the mains fails in order to transmit the data to a data collector.
The problem is that when the power supply fails a circuit controlled by the controlled, without using a relay, to put inside the non rechargable battery even if this event will be happened once in a year. Also the battery must not be parallel with any kind of load when not used, to save its energy. Therefore the leackage current from the battey goes in this circuit must be absolute 0 (I mean 0,00000000000000000000A). The battery must be discharged by itself as the manufacturer informs (less than 1% at 25 degrees each year)
I tried a mosfet circuit but the leackage current is anacceptable. Does anybody has any idea?
Thank you very much.