Therefore, it should be safe to use Ridgid 18V batteries with an adapter on Hyper Tough 20V MAX power tools. But you might consider disassembly your Ridgid 18V battery to ensure that there is an over discharge protection circuit. The Hyper Tough 20V MAX power tool hyper tough battery interfaces with the +, T, and… Continue reading Hyper Tough HT21-401-003-11 20-Volt MAX Lithium-Ion 4 0Ah Battery Pack