Can I charge a battery while it's outside of the vehicle, and what special precautions apply?

Yes, you can charge a battery outside the vehicle. Place the battery in a well-ventilated area and follow the same connection precautions as in-vehicle charging. However, marine (boat) batteries must be removed and charged onshore. Set the timer to OFF, clean terminals, connect the battery following proper polarity instructions, then set your desired charge rate and timer. When disconnecting, set the timer to OFF, disconnect the AC power, disconnect the negative clamp first, then the positive clamp.