Anyone isolate solar panels to controller cables?

[iain26]

Currently fitting my new panels and controller etc.
Instructions are very clear about connecting the controller to the batteries first or you could hear a disappointing pop!
there is an mcb to fit to protect the controller from the batteries but what happens when this trips, or when you disconnect the batteries to do any maintenance etc.
Does anyone remember to disconnect their solar cable BEFORE disconnecting the batteries or has anyone fitted an isolator between the panels and the controller?

 

[tonyidle]

Yes and yes. My isolator is a fuse so serves two purposes. There's a good reason to do so. The solar controller will initialise and needs a stable supply to do so. If it's dual (12/24) voltage it uses the connection to the battery to determine the correct configuration.

 

[iain26]

Yes and yes. My isolator is a fuse so serves two purposes.

Just in the +ve side?

 

[tonyidle]

Just in the +ve side?

Yes. The 0v side will be grounded at the controller anyway.

 

[Manic]

Yes, I disconnect them the night before I’m going to anything that requires battery to be disconnected.
Doing them at night save having to go up and cover them.

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[tonyidle]

Yes, I disconnect them the night before I’m going to anything that requires battery to be disconnected.
Doing them at night save having to go up and cover them.

But much easier to isolate them?

 

[Raul]

Yes, that will suffice. Just to point out that: the mcb you speak about between charger and battery, is to protect the cable NOT the charger. Also, it has to be rated for DC current. A mcb for AC current, will not work, or not able to break the ark of a DC current. Usually DC NH fuses are used to be able to contain the ark flame, or the midnite type magnetic breakers. Not AC mcb’s. I use a midi fuse in a holder, guaranteed to pop as intended, and the flame not open. At panels to controller, I use proper gPV ultra fast blow10x38 fuses in fuse holders on din, for each panel. That’s the only way to protect the panels nothing else. It has to be gPV ultra fast blow. If you really have loads and want lightning protection, you will need a SPD grounded to a rod. But, on mobile installations, we don’t do that.

 

[Reallyretired]

I have circuit breakers between panels and controller and between controller and batteries. I also have a sticker to remind me to operate them in the right order.

 

[DBK]

Disconnecting the batteries from the controller shouldn't harm the controller. Where it can get tricky is some controllers need the batteries connected first so they can determine if they are supposed to output 12 or 24 volts and with some even if they should be running at 48 volts. Victron, and perhaps a few other makes, remember what voltage they are to work at from the first connection so it subsequently doesn't matter in what order they are reconnected to the panels or battery. But if you don't have one of these it would be wise to disconnect the panels before reconnecting the batteries, just in case the controller forgets what it is supposed to be doing. . But this is the only reason, the controller will come to no harm being disconnected from the load.