Solar Component Selection 1120W System

[MNtal]

I'm go to start out by saying that I am going about this the wrong way, or at least in a manner that is different than most folks would approach choosing a solar system. If that bothers you, you have been warned, continue into my thread at your own risk.
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With the disclaimer out of the way I am looking for advice on selecting some of the system components, my budget is not unlimited but I understand larger systems come with larger price tags. I try and invest in quality components because I believe "Quality is usually remembered long after the price", and "I hate cheap crap".
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This is all going to end up on my MDT Freightliner Ambulance Project "THE RAMBULANCE" and be used boon docking 50-100 days a year and I would like to be able to tend the truck batteries off the system, run my AC and Refrigerators, or tie in when parked at home to take advantage of the system.
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Truck has a 270 Amp alternator
50 Amp Shoreline Power
4KW Onan Emerald Generator
2500W Vanner Inverter
3 Deka Starting Batteries in a separate 12V system
It also has a pretty robust Solid State Control System in the Horton box with an in Cab Control Panel unfortunately its kind of a pain in the buttocks.
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I currently have quantity four 280W solar panels that I was able to get at a fraction of the price they would normally go for. It was kind of a rite place rite time type of deal
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SolarWorld SunModule Mono 280W panels
MC4 Connectors
Pretty standard Commercial grade 24V Panels
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Panels are rated at:
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V = 31.2 VMP
A = 9.07 IMP
W = 282.984 PMAX
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Which means in series I am looking at a peak system capacity:
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1120W @ 124.8V @ 46.66A 24V system
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[video]http://www.youtube.com/embed/M6v2lDa8Hos[/video]
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I am looking for advice on selecting,
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50-60 AMP MPPT Charge Controller
- Thermal compensating
- Programmable
- Remote mount controller
- Low Voltage Disconnect
- Generator Startup Capability
- Blue Tooth or Rs232
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I am trying to decide between two possible candidates but I am open to other options as I am new to Solar. Each has their advantages and room to upgrade if I so choose, though the 100/50 is kind of at its peak capacity.
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Victron Blue Solar 100/50 MPPT @ $314
Victron BMV-702 Battery Monitor @ $191 or Victron MPPT Controller @ $79
VE Cable @ $16
= $414 or $520
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Best Prices I have Found have been @ Bay Marine Supply
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Outback FlexMax 60 MPPT @ $497
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Best Prices I have Found have been @ AltEstore.com
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DC Deep Cycle Batteries to run in a 24 Volt Cell
-Amp Hours TBD
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Right now I've looked at Discover batteries @$400 but I would like to be max around the $800 into the battery bank with the ability to add capacity down the road.
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DC/DC 24-12 Converter
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Victron 24/12 IP20 12-30A @ $50-130
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http://www.invertersupply.com/images/victron/fdssfd33.jpg
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All right that's enough from me how about it Guys and Gals?

 

[IdaSHO]

Looks like you are on the right track.

Component selection looks good. For controller, I would simply by the one that has the features you want.


One question though,

Is there any particular reason you want your battery bank to be 24V ?

 

[calicamper]

My LG 285s rated at 18% easily return about 200 watts on cool July Peak solar hour. Typical range is about 160-240 watts. Temps can impact production also. 15-30% hit when temps are pushing 90+. I see micro inverters reporting 140 degrees often at the panel. They sit with about 4inch air flow gap over spanish S tile.

Just to give you some general ideas on typical power output on the larger panels.

My big system is 8.2kwh 29 285watt LG panels running micro inverters. On a cool july day we hit 50kwh generated by sun set.

I think your on the right track but I wouldn't expect much more than 200 watts out of each panel on a typical day at peak gen.

 

[dwh]

Have a look at Midnite Solar. The Classic has a ton of features and since it's designed for either solar or wind, I can think of some nifty tricks to use the dump load relay for (since you dont need a dump load with solar, it's a spare relay).

Just one example..battery bank is full but solar can still produce? Use the dump load relay to turn on a heating element in the hot water tank. Or UV in the freshwater tank.

Plus it's got Ethernet and on board web server. I bugged them years ago when they were developing the Classic to add SNMP so it could be polled via single board computer like a Raspberry Pi and then use MRTG to make graphs. Dunno if they ever did though. Pretty sure they have different firmwares for specific situations.

 

[MNtal]

Is there any particular reason you want your battery bank to be 24V ?

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The Panels to my understanding, and I could be wrong, are better utilized at 24V vs 12V. ???
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Both of my refrigerators an Edgstar 66Qt Cooler chest Freezer (85W@2.5A), and a very small Norrcold (_____) are capable of running off 12/24DC or 115V AC and to my understanding 24V DC is the most efficient.
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My AC unit will need to run off an Inverter, I purchased a Frigidaire Window Unit 5000 Btu (410W@3.8A w/ EER12.2) it was $167:sombrero:.
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I think your on the right track but I wouldn't expect much more than 200 watts out of each panel on a typical day at peak gen.

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That's kind of what I was expecting hence the reason I was looking at the Victron 100/50 Controller, the price point is definitely appealing.
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Have a look at Midnite Solar. The Classic has a ton of features and since it's designed for either solar or wind, I can think of some nifty tricks to use the dump load relay for (since you dont need a dump load with solar, it's a spare relay).

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the Midnite Solar Classic 150-SL or 200-SL look like decent Units, I especially like the MADE IN USA.
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150V/96A @$515 or 200V/79A @ $528
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Can anyone explain ARC Fault Protection to me?
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Does anyone Know if the Midnite units can be setup to turn the Genset on with a low voltage function?

 

[carbon60]

This fellow has a ton of rants/information:

https://handybobsolar.wordpress.com

Very worthwhile reading.

A.

 

[dwh]

If you are running an MPPT controller then you can run your PV array at 24v (or whatever) but still have your battery at 12v.

Arcfault...

Well, breakers are there to protect the wire, but they actually aren't very sensitive and it usually takes a pretty hefty overload to trip a breaker. Of course, a dead short will always do it, but a partial short (or leak) might be enough to generate enough heat to start a fire, but without generating enough over current to trip a normal breaker. An arcfault device is like a breaker with a very sensitive, fast acting bit added on that detects a specific condition. Similar to a ground fault circuit interrupter.

I'm 99.9% certain that the Classic has a programmable relay for generator start, but they've got a few variations of the Classic these days and who knows...they might not all have it. Check with them.

 

[dwh]

Splitting hairs here, I suppose how one defines "partial"... But leakage or partial short without arcing is viewed as simply added load.

Split hairs all you want. On a phone, thumb typing, I stick to KISS principle and leave it to others (with real keyboards) to fill in the blanks.

I like to think of it as "load shifting".

 

[IdaSHO]

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The Panels to my understanding, and I could be wrong, are better utilized at 24V vs 12V. ???

Ah, thats what you meant.

Yes, far better to run 24V panels on a 12V system.

MPPT will make perfect sense of it, and it translates into a very efficient system.

 

[rossvtaylor]

Have a look at Midnite Solar.

Yes, this! We just made the same selection decisions you did, for our Freightliner ambulance, and we got a Midnite Classic. A quick bit of background... my primary career, for the moment anyway, is in renewable energy. Granted, I'm primarily a wind guy but I've had enough experience with solar and hybrid systems that I've used a lot of different equipment. I've put Outback stuff in pretty harsh environments... it's tough stuff. The Trace/Schneider/Xantrex controllers are tough, too (but pretty basic). But, I think the Midnite stuff is heads above those. The company owner actually started Outback... he's a genius and a damned nice guy, who cares about quality. US made, bulletproof quality, accessible and knowledgable support, and great features for the price. BTW, check out their surge suppression devices (SPDs) too! For $100, every home should have one.

Good call, DWH.

 

[MNtal]

If you are running an MPPT controller then you can run your PV array at 24v (or whatever) but still have your battery at 12v.

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If 4 of My panels (1120W) are in series, I'm theoretically running them PEAK (Magic Land) 124.8V@9.06A to the controller.
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The controller takes that 124.8V and drops it down to 24V for the battery bank but in doing so increases the amperage by the same factor so it doesn't lose any power. (MPPT vs. PWM)
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124.8V / 24V = a factor of 5.2
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5.2 x 9.06A = 24V@47.A = 1120W
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(Please excuse the rounding errors)
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But more realistically in the (Real World), where we live, breath, and things don't always work out exactly as planned. I'm looking at 55%-85% output @62.4V-106.V going to the controller.
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Doesn't it make more sense to run a 24 Volt system? Forgive me, I'm from the North where kinda slow up-der-ya-know. (serious question, I really don't know)
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Where I live and where the System will be primarily used it has a potential for 4.0-6.0 kilowatt hours (Kw/H) per day, depending on which pretty picture you look at. I'm basing that estimate off of the pretty pictures on Google images, and the experience of the friend that sold me the panels.
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@ 55% Efficiency
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(1120W x .55 = 616W@25.67A)
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4.0 x 616W = 2464W
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2464W = 2.464 KW/H per day of charge produced by the panels at 55% efficiency.
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@85% = 3.808 KW/H per day of charge produced by the Panels.
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What are the down sides to running a system in 24V vs. 12V?.
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[IdaSHO]

There is no down size to running a higher voltage array.
On the other side of things, there is little benefit to run at HIGHER voltage than 24V on a 12V system.


Ultimately, it will most certainly come down to the max input voltage of your charge controller.

Id choose your controller, then wire the panels in such a way to provide input voltage no higher than the stated max for the controller.


Or just make is stupid simple, run 24V panels, and keep them in parallel

 

[MNtal]

There is no down size to running a higher voltage array. On the other side of things, there is little benefit to run at HIGHER voltage than 24V on a 12V system.

I guess what I was asking is there a reason not to run my batteries in 24V?

Yes, this! We just made the same selection decisions you did, for our Freightliner ambulance, and we got a Midnite Classic.

BTW, check out their surge suppression devices (SPDs) too! For $100, every home should have one.

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Which Model did you purchase? 150-SL or 200-SL or other
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Their naming convention kinda erks me.
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I will check into the SPD systems thanks.

 

[dwh]

The MPPT is going to operate the array at the array's Vmp. The Vmp will change a bit based on temperature and the angle that the photons are hitting the PV. So the MPPT will adjust the voltage that the array operates at to keep the array in the sweet spot to get the max watts out of the array based on whatever the current conditions are.

That's gonna happen no matter if you rig your array in series or parallel or two series strings paralled.

But the array voltage isn't going to change all that much. If your array is only putting out at 50% efficiency, that will show up as 50% less current (amps), not 50% less voltage.

Then the buck converter will lower the voltage to battery charging voltage and then feed that through a PWM circuit to charge the battery.

By lowering the voltage, amps is increased. But watts is watts. 1100w into the controller is gonna be 1100w out of the controller.

Of course, the PV always has to have a Vmp higher than the battery voltage or it can't charge the battery. But even a "12v nominal" PV will have a Vmp of at least 15v.

Your modules, in parallel, could charge either a 12v or 24v battery bank. To charge a higher voltage bank, you would be required to rig in series to raise the array voltage.

It doesn't matter if you rig the PV in parallel or series, and it doesn't matter if you run your battery bank at 12v or 24v...the MPPT is gonna stuff the same watt*hours into your battery either way.

The only real advantage to going to higher voltages is that you can use skinnier wire, which is something that starts to really add up on a 5kw or 10kw home system but doesn't matter all that much on a small mobile system.

If your truck has a 12v chassis electrical system, then I'd rig the house battery bank to 12v so it could charge off the trucks alternator. If the chassis is 24v I'd rig the house bank to 24v, same reason.

I'd rig the PV array in parallel because either way, the Vmp is high enough for battery charging, and rigged in parallel is redundant. Use a 4 breaker disconnect/combiner from Midnite and if one module craps out or eats a tree branch and gets broken, just flip the disconnect for that one module and keep on truckin' with 3 modules.

 

[calicamper]

I think all the smart modules detect if your system is 12v or 24 and handle the battery side as such. The solar side as long as its within the top max input limit your fine. My cheap O $30 controller does this. Its max input is 20amps then its crispy fried. But my little set up is only 2 10watt panels charging a 18ah battery.