It says to limit the testing to no more than 10 amps but I don't recall a time limit. I would not consider that a "parasitic" draw. That is a major draw. Did you go to their website and see what they said. I can if you want me too. It can also serve as a battery to save memory, if changing out the main battery.
IV. Precautions 1. This product can only be connected to the OBDII port of a car to complete the corresponding functions. Please do not connect it directly to active devices without using the OBDII port. Before connecting to the OBDII port, please make sure that the car’s OBDII port is a standard OBDII port and the wiring is correct. It is recommended to verify that there are no major faults in the car’s power supply system before connecting the unit. If the OBDII port is not standard, wiring errors and other reasons cause damage to the machine or car circuit, our company will not be held responsible. 2. The maximum output current of this product is 10A. The limited current of the OBDII port of some cars is lower than this value, and there may be current limiting measures such as fuses. Therefore, after connecting the Smart Output of this product, it is recommended not to make the current of the entire car system greater than the limited current of the OBDII port of the car itself, so as to avoid problems such as the car’s own OBDII fuse being blown.Do not input voltages exceeding the device’s range (30V) into the OBDII port. If a voltage exceeds the range, disconnect the voltage as soon as possible. If the voltage exceeds 30V, an overvoltage warning interface will be displayed. 3. The device can output a maximum of 10A current. If the current exceeds this limit, an overcurrent warning interface will be displayed. Do not output current exceeding 10A for an extended period. If an overcurrent warning appears, restore the current to normal as soon as possible. 4. The device can output a maximum of 10A current. If the current exceeds this limit, an overcurrent warning interface will be displayed. Do not output current exceeding 10A for an extended period. If an overcurrent warning appears, restore the current to normal as soon as possible.