Yeah, it might be a bit much. I'd like to find a charger with an adjustable final voltage. Then I could limit it to 16.0 volts. That would also make the battery pack last longer. I think Steve H said the SL could handle voltage up to 18.0, but I'm not sure of that. Best bet is to stay at, or below 16.0. One of these days, I'll get around to doing a test to determine how much extra depth, and/or sensitivity you get from the increased voltage. I do know my SL will detect a 1 grain gold bar at 1 1/2" in an air test, which isn't bad.
Jim