Maximum allowable voltage input to the 3554 Battery Tester
The protective fuse will blow before 100V DC is reached on the 3554.
For your reference, the fuse blows at +/-110V DC or 80V AC (50/60Hz) on the BT3554.
The fuse rating is 250V, but is voltage applied between both ends of the fuse.
Therefore, it is different from the voltage measured between input terminals.
The input voltage is divided by the circuit and the lower voltage is applied to the fuse.