A battery apparatus, comprising: a plurality of first battery cells (B-1,B-2,..., B-K) connected in series with one another; a switching circuit to selectively couple first and second switching circuit nodes (202,204) with a selected battery cell of the plurality of first battery cells; a balancing circuit to transfer charge between the selected battery cell and a second battery, the balancing circuit including: a first pair of battery connections (321,322) coupled with the first and second switch circuit nodes (202,204), a second pair of battery connections (331,332) adapted for coupling with the second battery, a transformer, including: a first winding wound around a transformer core and coupled with the first pair of battery connections, a second winding wound around the transformer core and coupled with the second pair of battery connections, and a third winding wound around the transformer core, a first rectifier circuit coupled to receive a signal from the third winding, the first rectifier circuit operative to provide a first rectifier output signal according to the signal from the third winding, a first transistor coupled between the first pair of battery connections (321,322) and the first winding, the first transistor including a first control terminal, a second transistor coupled between the second pair of battery connections and the second winding, the second transistor including a second control terminal coupled to receive a signal from the second winding responsive to current flow in the first winding to allow current flow between the second winding and the second pair of battery connections, and a first control circuit responsive to a first enable signal transitioning to a first state to provide a first pulse signal to the first control terminal of the first transistor to turn on the first transistor to allow current flow in the first winding, the first control circuit being responsive to the first rectifier output signal indicating current flow in the second winding below a threshold value while the first enable signal remains in the first state to provide a further pulse signal to the first control terminal of the first transistor to again turn on the first transistor. a plurality of first battery cells (B-1,B-2,..., B-K) connected in series with one another; a switching circuit to selectively couple first and second switching circuit nodes (202,204) with a selected battery cell of the plurality of first battery cells; a balancing circuit to transfer charge between the selected battery cell and a second battery, the balancing circuit including: a first pair of battery connections (321,322) coupled with the first and second switch circuit nodes (202,204), a second pair of battery connections (331,332) adapted for coupling with the second battery, a first pair of battery connections (321,322) coupled with the first and second switch circuit nodes (202,204), a second pair of battery connections (331,332) adapted for coupling with the second battery, a transformer, including: a first winding wound around a transformer core and coupled with the first pair of battery connections, a second winding wound around the transformer core and coupled with the second pair of battery connections, and a third winding wound around the transformer core, a first winding wound around a transformer core and coupled with the first pair of battery connections, a second winding wound around the transformer core and coupled with the second pair of battery connections, and a third winding wound around the transformer core, a first rectifier circuit coupled to receive a signal from the third winding, the first rectifier circuit operative to provide a first rectifier output signal according to the signal from the third winding, a first transistor coupled between the first pair of battery connections (321,322) and the first winding, the first transistor including a first control terminal, a second transistor coupled between the second pair of battery connections and the second winding, the second transistor including a second control terminal coupled to receive a signal from the second winding responsive to current flow in the first winding to allow current flow between the second winding and the second pair of battery connections, and a first control circuit responsive to a first enable signal transitioning to a first state to provide a first pulse signal to the first control terminal of the first transistor to turn on the first transistor to allow current flow in the first winding, the first control circuit being responsive to the first rectifier output signal indicating current flow in the second winding below a threshold value while the first enable signal remains in the first state to provide a further pulse signal to the first control terminal of the first transistor to again turn on the first transistor.