This and all other rectifiers need an adequate size aluminum heat sink. The heat sink to handle .7 volt drop at a 70 amp load would be EXACTLY the same as what is found in a 70 amp battery isolator. You would do well to consider using such an isolator in fact.
One rectifier will drop voltage .7 - .9 volts. If the power supply is set to 15.00 volts, the rectifier will output 14.1 to 14.3 depending on load. Two silicon rectifiers in series will usually drop voltage 1.5 volts. Your 15.00 volts will drop to 13.5 The voltage drop is even from low to high current, and low to high voltage.
EXAMPLE: I am using (3) 1N4003 diodes in series to drop 12.1 volts power supply output to 9.9 volts for a single 10 watt, 10 volt LED device.
But .7 to .9 volt per series rectifier is all you're going to get and even then you are going to need an impressive heat sink.
Your issue is you are dealing with magnitudes greater current.
