I wouldn't do that. Lead acid cells need a constant voltage (variable current) charge. Which means it will take gradually less and less current as the battery reaches its full charge. The Piranha is set up for the types of cells measured above, which need a constant current charge. You would be better off using a regular car battery charger on its lowest setting, a float charger such as the Battery Tender Jr., or purchasing a peak charger that can also handle lead acid cells such as the MRC Super Brain 977.