Adding to solar

[Yarome]

I wish the OP could do something about that 18' from the controller. That's a lot.

 

X2. 36' run total (array>controller>battery bank) is 'massive'.

[Jim Gell]

When I needed to reduce wire diameter in a situation like this I snipped strands from the center of the wire bundle and scrunched the outer layer down enough to go in the clamp. A tiny wire tie does a good job of keeping things scrunched down as you try to get it into the clamp.

That's a great tip, Stan. Thanks.

[Phaeton10]

I just talked to tech support at NASW and gave him my wiring size from beginning to start and he assured me that # 4 will be all I need from controller to the batteries at 12 volt and wired in series with 2 strings. He stated this would be less than 2%. I am still going with #1, that I found for $ 2.88 a foot. Will use Stanley's tip about cutting out the center.

[Yarome]

I just talked to tech support at NASW and gave him my wiring size from beginning to start and he assured me that # 4 will be all I need from controller to the batteries at 12 volt and wired in series with 2 strings. He stated this would be less than 2%. I am still going with #1, that I found for $ 2.88 a foot. Will use Stanley's tip about cutting out the center.

 

It's good to get multiple opinions, but it's hard to argue physics. For an 18' 12v 54amp run with #4 (starting voltage @ 13v ending with 12.76v) would give you 3.76% loss. I think you're making a good choice with the #1. With the same set, that will bring you up to a 1.85% loss. All of which is assuming ideal conditions and minimal resistance points at all connections. If you run to capacity (80amp) then #1 will keep you above 3% @ 2.77%. Which would be 'acceptable' when you balance cost to loss. Ideally, <1% 'built in' to the system is where we try to be, but for 18', running 4/0 is not cost effective against the gain.

 

You have to bear in mind that many people tend to stick with ampacity charts they find on the internet. They are NOT a one size fits all guide to ampacity. Most are gauged on an 'unwritten' 3% "non-critical" loss. However, were not talking standard DCV with an active supply. Solar production is finite, so 'any' loss is critical. IMO

 

It's important to use a reliable calculator (like the one Jack linked to) to make an informed decision. Online charts will get you in the ball-park, but can be very misleading when it comes down real life application.

[Jack Mayer]

 

 

You have to bear in mind that many people tend to stick with ampacity charts they find on the internet. They are NOT a one size fits all guide to ampacity. Most are gauged on an 'unwritten' 3% "non-critical" loss. However, were not talking standard DCV with an active supply. Solar production is finite, so 'any' loss is critical. IMO

 

It's important to use a reliable calculator (like the one Jack linked to) to make an informed decision. Online charts will get you in the ball-park, but can be very misleading when it comes down real life application.

 

 

I see this stuff all the time. Use of either the wrong information in calculations or use of the wrong chart. It is all about the physics. It is not debatable. Use the right calculator and put in the right numbers and you will get an accurate answer. Then you can make an informed decision like in Yarome's post above.

[hemsteadc]

Does a 3% loss equate to harvesting 97ah instead of 100?

[Yarome]

Does a 3% loss equate to harvesting 97ah instead of 100?

 

That would be very difficult to calculate and there is not a simple answer because there are so many variables at play.

 

Basically, your looking at loosing 3% of the charge voltage. So... say your controller is sending out 14.8v in a bulk charge. You're batteries would only actually be getting 14.3v's. Since your solar generation time is finite in any given day, it would have an impact on how much of a charge your battery bank would actually receive since there may not be adequate voltage to 'push' the amps that it requires. Is that muddy enough?

[hemsteadc]

 

. say your controller is sending out 14.8v in a bulk charge. You're batteries would only actually be getting 14.3v's.

Could the Outback be configured to 'overcome' that little problem by setting the Bulk voltage higher?

[Yarome]

Could the Outback be configured to 'overcome' that little problem by setting the Bulk voltage higher?

 

Theoretically, sure. If it's capable of custom settings and has a high enough upper limit. Of course, I don't know how that might affect any other 'behind the scenes' algorithms. Ie., temp comps, equalization..

 

I say "theoretically", because I'm really not familiar enough with Outbacks to give an educated answer to that. I've seen it done with "dumb" chargers... but not so much with smarts or solar controllers. Not that it isn't common.. it's just not in my frame of reference. I'll look around a bit on that.

[Jack Mayer]

One thing to bear in mind....if there is a voltage sense line from the controller to the battery bank then the controller "may" be able to compensate for voltage drop across that connection, since it can sense endpoint voltage and automatically boost it. That depends on the controller and how much loss there is.....

[Yarome]

 

I see this stuff all the time. Use of either the wrong information in calculations or use of the wrong chart. It is all about the physics. It is not debatable.

 

No joke there. I won't disparage anyone's reputation online, but there are only a couple or so retail solar companies that I wouldn't have any qualms about recommending to someone.

 

When you're spending hard earned cash on decent solar components, getting cheap on the wiring (the backbone) to save 50 bucks doesn't make good sense.

[earlvillestu]

One thing to bear in mind....if there is a voltage sense line from the controller to the battery bank then the controller "may" be able to compensate for voltage drop across that connection, since it can sense endpoint voltage and automatically boost it. That depends on the controller and how much loss there is.....

It may be able to step up the voltage, but it cannot compensate for the power lost in the wiring.

[Jim Gell]

It may be able to step up the voltage, but it cannot compensate for the power lost in the wiring.

I don't know much about electricity, but I was thinking if energy was lost to resistance, resulting in heating the cable, that energy is gone.

[Mark and Dale Bruss]

What Jack was referring to is when the controller changes what it feeds into the batteries. For example, if the voltage loss was .1 volts, and the controller was going to feed the batteries until they reached 13.7 volts, the batteries would only get 13.6, not the desired target. (These are reference numbers). By reading the batteries by a secondary sense circuit, the controller can allow more voltage.

 

Power (volts x amps) lost to resistance is gone for ever. The controller takes what power is generated by the panels and tries to put as much of it as possible within the limits of what the batteries can handle.

[Jim Gell]

Like I said, I don't know much about electricity. Some may say I know just enough to be dangerous. But I think I actually understand what we are talking about here. With the right equipment you could get the right charging voltage at the battery by increasing the voltage leaving the charger to compensate for what is lost to resistance on the way.

[Jack Mayer]

You got it Jim....

[oldjohnt]

From an engineers prospective, even though were dealing with 12 or 24 or 36 or even 48 or more volts DC, I still use Voltage Drop charts or calculators for 120 to 480 volt AC wiring systems. To best harvest all the energy my solar panels are providing, I prefer to deliver as much as reasonably possible (Id call using 500 MCM cables a bit extreme lol) it into my solar charge controller versus wasting it as I Squared R heat energy in the wire from panels to controller. To agree with something posted somewhere above, if youre spending big bucks on panels and controller etc DONT SCRIMP ON WIRE FROM PANELS TO CONTROLLER. If the wire is too small that's heat energy into the ambient versus electrical energy into your charge controller. Of course, higher operating voltages at your net panel output means you can get by with smaller wire to your controller and the input voltage ranges of your controller determines that maximum. Subject to shading concerns and your charge controller and panel matching problems I prefer higher operating voltages such as 24 or 36 or 48 etc versus only 12 (talkin nominal here). Although I prefer matched panels, mis matched in series concerns me less then in parallel.

 

John T From Bishop California

[Dale P]

the panels are all 17.7 volts there is no problem

[Retiredin1993]

Well today is the first day from out under the trees sense my install and my set up was producing 26 amps out. The sun was partially covered by clouds, so I don't think I was getting full advantage of my system. It was a quick looks as I had other things going on. I think I will see an improvement this winter when we will be doondocking for the winter.