The WF-9540 model provides 40 Amps and a clean, constant 13. 6 VDC nominal output for reliable operation of electronics and appliances. Automatic three-stage charging extends the life of your battery with output voltage modes of 13. 2 VDC range “float” mode, 13. 6 VDC range “absorption” mode, and a 14. 4 VDC range “bulk” charge mode. The 9500 Series also maintains peace and quiet, as the cooling fan runs only when needed.