Genius1 1A Fully-Automatic Smart Charger

This NOCO GENIUS1 charger is $23.77, down from $39.95 at Amazon. It's the best deal we've seen for this model. It works on both 6-volt and 12-volt batteries, including lithium-ion and lead-acid types, and can charge batteries as low as 1 volt or fully dead batteries using its Force Mode. A built-in thermal sensor adjusts the charge based on ambient temperature.