If you have two 175 watt panels each at 42 volts you will need two 8 amp 45 volt diodes.
Installing blocking diode solar panel.
For solar panels we recommend you put one blocking diode on each solar panel inside an abs project box.
In short as diode only passes current in one direction so the current from solar panels flows forward biased to the battery and blocks from the battery to the solar panel.
In this video you will learn the importance of a bypass diode in solar panel learn how to connect a bypass diode to your own solar cells to improve the eff.
Learn how and why blocking diodes and bypass diodes are used.
A blocking diode and bypass diode are commonly used in solar energy systems and solar panels.
Diode and unidirectional flow of current.
The diode needs to have a voltage and amperage rating above that of the panel.