wiring solar output

[sailorboy1]

So is there a best/better/difference on where you wire the solar controller output to in order to supply the batteries? The choices I see are:

1 - directly to the batteries (the hardest considering there are 2 banks)
2 - to the DC panel supply via the DC main panel (seems the easiest)
3- to the alternator supply point on my isolator (makes use of the current selector switches etc)

And for all choices proper breaker/fuse protection and wiring sizing is will be in place.

[Dreaming Yachtsman]

Don,

You don't give us any information about the arrangement so this suggestion may seem trivial. You want to keep your cable run between the charge controller and the batteries as short as practical. Given that caveat, go with the easiest installation.

[Dsanduril]

Don,

chum in water, sharks circling, smell blood. Did you really ask about "best" and "solar" (Mods - need a shark smiley).

+1 to what Dreaming said. I'd probably vote for your alternator connection point, as that presumably allows you to choose where you charge independent of which battery you are using at the time. Most times you'll want to charge where you're using, but being able to send it other places is nice. But really, whatever gets it into the batteries with the least losses (all appropriate protections in place as you noted).

[sailorboy1]

I don't think it really matters how long the wire run is as long as it is taken into account on wire size. But either of the 3 options I list is going to be within 6 feet difference (I probably will oversize the wire and size for twice the expected current amps as I may want to add a second panel someday).

PS - with my current wiring landing the solar supply at the main DC panel also allows the batteries to be isolated to the point that the on service bank (which is normally both) is being charged. But landing at the alternator I could charge a bank that is off service (I would expect that that would mean it had a problem and in which case I would probably physically disconnect it)

[nigel1]

Don, when you say 2 banks, is that two house banks, or house and engine bank. Dont think it is worth wiring direct to engine bank.
To a selector switch sounds OK, then you could charge the engine bank if really needed.

[sailorboy1]

Originally Posted by nigel1

Don, when you say 2 banks, is that two house banks, or house and engine bank. Dont think it is worth wiring direct to engine bank.
To a selector switch sounds OK, then you could charge the engine bank if really needed.

2 banks means 2 house banks that I always run together, but can isolate each if needed

whether I run both house banks together or only 1 bank the start battery will also charge from the house batteries with any of the options (but if I wired directly to the batteries I would have to physically disconnect 1 if it goes bad because I'm not going to put in a 3 way switch to make it "easier" for something that is a .01% odds concern)

[Dsanduril]

When you get right down to it, not actually charging the batteries is the best use of the solar electricity, so if you run it to the house panel and are using and charging from the same bank that's generally the best way to operate. That way the solar stuff doesn't have to go through the inefficiencies of the charge-discharge cycle. If you are producing more than you are using then the difference goes into the batteries, if you are using more than you are producing then the batteries make up the difference.

If, however, you want to be able to use your solar to run something like an equalization charge then you need to be able to do it on the out-of-service bank. This usually doesn't work because the sun isn't up for long enough and steady enough to allow a full equalization, but it does get tried and most controllers have that mode.

[RDW]

I am a total beginner but I would think you would want to be charging as many cells as possible since at the upper end of charge the batteries take charge more slowly. I have thought that if I was having to charge with engine alternator and solar, that I would try to run the engine very early in the day so the solar could slowly top off the batteries thru the sunny part of the day. Do I need a few more windows in my cabin or is this reasonable.
RDW

[djmarchand]

If wiring to the main DC breaker on the house panel is short, go with that approach. And if your main breaker is the right size, you may not need a separate breaker to protect the wire to the controller and solar panels.

FWIW you need fairly large size wire to limit the voltage drop from the panels. So you will probably be using at least 10 gauge wire which can safely carry 60 amps. Most main panel breakers are 30 or 50 amps.

David

[twistedtree]

I too would go for the main panel. Then you can have all your breakers in one place. It will probably also result in your amp meter (if you have one) reading the net current in/out of the batteries.

[Uncle Bob]

Originally Posted by Don Lucas

So is there a best/better/difference on where you wire the solar controller output to in order to supply the batteries? The choices I see are:

1 - directly to the batteries (the hardest considering there are 2 banks)
2 - to the DC panel supply via the DC main panel (seems the easiest)
3- to the alternator supply point on my isolator (makes use of the current selector switches etc)

And for all choices proper breaker/fuse protection and wiring sizing is will be in place.

Hi if I remember correctly when I installed my morningstar charge controller the instructions said connect to the battery or as close as possible to the battery with an appropriate fuse.

[Maine Sail]

Don,

You mention an "isolator".. Is this a diode type battery isolator? if so you will encounter voltage drop through the diodes, but beyond that your solar controller might not even turn on if connected to the input stud of an isolator. Most solar controllers need to sense bank voltage to turn on.

I prefer to run direct to the house bank, properly fused, as it allows for accurate voltage sensing of the bank.

[Bash]

Controller to fuse to bank.

[senormechanico]

Ten gauge carrying 60 amps?
30 is more like it.

[sailorboy1]

Originally Posted by Maine Sail

Don,

You mention an "isolator".. Is this a diode type battery isolator? if so you will encounter voltage drop through the diodes, but beyond that your solar controller might not even turn on if connected to the input stud of an isolator. Most solar controllers need to sense bank voltage to turn on.

I prefer to run direct to the house bank, properly fused, as it allows for accurate voltage sensing of the bank.

It's one of those "non-diode" Victron isolators that isn't suppose to have any voltage drop across it.

But the house bank is wired to the input post with the alternator input and only the line to the start battery has to go across the isolator.

I don't think there would any losses etc in using that circuit.