The "Turbo" setting is why people search for the instruction link. Used improperly, it will fry your battery.
When to use Turbo Mode:
The Official Turbo Procedure (from the manual): selmarturbo4batterychargerinstructions link
Warning: Leaving the charger in Turbo mode for 20+ minutes without a load will boil the battery dry. The "Turbo" setting is why people search for
The Selmar Turbo 4 interface usually features: The Official Turbo Procedure (from the manual):
Instruction: Start on "Medium". Never start on "Boost" with a completely flat battery.
Before connecting any cables, the operator must familiarize themselves with the unit’s interface. The Schumacher Turbo 4 typically features a large front face with a voltage meter and two distinct control knobs.