I just replaced the 12 volt car battery that I use for my vhf radio. I have no way to know how low the battery or when to re charge it or how to test it to see how much is left in it before before re charging. My outboard is a pull start my running lights and cabin lights are liquid fuel There is no electric power on the boat other than the vhf battery. Anyone know what kind of meter I need to test the battery and where to get it.