Solar panel wiring advice needed

[mojoman]

I'm getting ready to install my solar panels, (4) 100 watt 12v. I'm going to wire 2 sets of panels in series then parallel the two, now 24v sets into a MPPT controller. Would you put blocking diodes anywhere or fuses? I'm going to put in a circuit breaker before the MPPT controller. I know the panels have diodes but when you put them in series…… its all magic to me so I need advice. I can order MC4 connectors with a fuse or diode. Or should I put them all in series for 48v?

[markopolo]

Good article on fuses in solar installations here: https://www.windynation.com/jzv/inf/how ... -pv-system

And good info on diodes here: http://www.solar-facts.com/panels/panel-diodes.php

In series installations By-Pass Diodes are used. Panels usually have Blocking Diodes already.

I've had 4 rigs with solar but all were 12v, single or parallel panels and basic controllers so I don't have the experience to help much.

[mojoman]

Thanks, I ordered two bypass diodes.

[booster]

You probably want to check with the supplier of the panels to see if they are needed. Many panels come with them already in the panel box. You don't really want to be adding more if you don't need them.

If you are looking at bypass diodes, you must be going to go series on two parallel pairs for a 25v nominal voltage. Be sure to check to make sure you charge controller can handle the voltage. You can't go by the nominal, you need to go by the max open circuit for the panels. On our 12v nominal panels that is nearly 18 volts max open, so a series set would be over 35 volts max open. Your controller should say what the max open voltage top end is, and you have to stay below that. It will also need to be MPPT for series.

[mojoman]

The description for the panel listed a 2-diode junction box, does the second diode bypass the entire panel or half the panel ?

[mojoman]

My MPPT controller is rated up to 150v.

[booster]

I think that they are setup so that each diode will bypass 1/2 of the panel so they can work independently in the shade or if there is a failure.

[mojoman]

I ordered 2 bypass diodes, should I use them?

[booster]

From what I have heard and read, if they are in the panel box, they should be all you need, unless you want to put in blocking diodes. Most folks don't seem to use the blockers, probably because they go in the current carry lines and cause a .4-.7 volt drop.