To measure battery life is time consuming task and providing high load to discharge the battery don’t provide reliable result.
Hence this circuit constructed with IC MAX921 and a analog clock to measure accurate battery drain duration, this is a application not for MAX 921 IC from maxim integrated.
Circuit diagram for battery drain meter
Construction and Working
This circuit constructed with IC MAX 921 and analogue Quartz clock, here the analogue clock connected with battery (1.5 volt AA size) and -Ve terminal of clock connected with drain terminal of MOSFET this is controlled by the output of IC MAX 921 and this circuit is powered by the testing battery when the testing battery dryed means then there is no output from MAX 921 so the MOSFET drain open.
Hence the analogue clock stop at particular hour by observing the clock we can get to know the battery drain range.
You can get datasheet of IC MAX921-MAX924 here.