  Quantum batteries have significant potential applications for future industry
and daily life. The capacity is an important indicator for a battery. Methods
to improve the capacity of quantum batteries are important. We consider quantum
batteries given by bipartite quantum systems and study the enhancement of the
battery capacity under local projective measurements on a subsystem of the
quantum state. By using two-qubit Bell-diagonal states and X-type states as
examples, we show that quantum battery capacity with respect to the whole
system or a subsystem can be improved by local projective measurements. Our
theoretical analysis will provide ideas for the experimental development of
quantum batteries.
