The main battery fuse of a car is a relatively high amperage fuse that protects the overall battery circuit. When it gets blown, it causes problems like no crank and other accessories not working.
When the high voltage battery of a hybrid car becomes weak, there is a significant increase in spending on gas due to fast drain and frequent recharge.
Current measurement is best done by clamping the conductor carrying the current instead of having an ameter in series. This method is good for measuring parasitic battery drain.