[XuLeTZ]

Diagnosis on Saturday BMW M5 F11 first several minutes 67A
but I only set it to 13.8V,
  (ista from icom next the original showed 13.6V)
probably at 14.4V it would be over 80A
after a few hours the ignition dropped to 35A / 13.8V
Very good facilities,
Gysflash 100-12-HF

Increasing the voltage will lower the amps. Lowering the voltage will increase the amps. that`s how is working. So best to keep it at 13.8V with 67A. If you need higher amps, lower the voltage.
Any supply has written on the label. 220V - 1200W - 12V = 100AMPS (this is an example, like connecting it to 220V at your home socket)
So that means it will produce 100Amps at 12V. Now, if you increase the voltage, use the simple math. Wattage divided by voltage equals amps. Eg 1200W/12V=100Amps
let`s increase it to 13.8V - 1200W/13.8V=87A (86.95652173913043)
So don`t increase the voltage if you need more amps