Keep peace of mind when using your motorized and recreational vehicles equipped with lead-acid batteries. First, select properties that apply to your battery or set of batteries from different types and uses. Using a voltmeter, measure the voltage and enter it. This displays back the level of charge in percentage. Cases requiring the use of a hydrometer are also supported. Please note that the use of this app requires a voltmeter and or hydrometer. Version 1.1 Your feedback is very apprec