A lead-acid battery comprising: at least one lead-based negative electrode; at least one lead dioxide-based positive electrode; at least one capacitor electrode; and electrolyte in contact with the electrodes; wherein a battery part is formed by the lead based negative electrode and the lead dioxide-based positive electrode; and an asymmetric capacitor part is formed by the capacitor electrode and one electrode selected from the lead based negative electrode and the lead-dioxide based positive electrode; and wherein all negative electrodes are connected to a negative busbar, and all positive electrodes are connected to a positive busbar. The capacitor electrode may be a capacitor negative electrode comprising carbon and an additive mixture selected from oxides, hydroxides or sulfates of lead, zinc, cadmium, silver and bismuth, or a capacitor negative electrode comprising carbon, red lead, antimony in oxide, hydroxide or sulfate form, and optionally other additives. The capacitor electrode may be used in asymmetric capacitors and batteries of other types.