Get a digital multimeter. This is a must-have to keep an eye on your batteries. They are available at all hardware stores and many department stores (like Walmart). You can also quickly check resistance with them, but probably not as accurately as with a 510 ohm checker (which I assume you already have). I only use a multimeter I got for about $25 at Home Depot.How do u check that? I can check my coils, but i only have a intellicharger for the batteries