We point out that a battery may be designed so that in a gravitational field it will have a gravitationally induced emf in addition to an electrochemical one. The gravitationally induced emf of a battery with a small 'effective' electrochemical potential and a long 'effective' length can readily be measured to very high precision by means of any precise voltmeter, and in particular by a Josephson junction. Such a device may be employed to measure any component of the gravitational acceleration vector. It can be constructed compactly enough to be placed down a borehole. Thus, in principle it is an extremely precise and adaptable tool for geophysical exploration.