Designing a Solar System for a Buddy who almost burned his place down

[ADDvanced]

So my off grid neighbor built a small cabin, and on the roof he mounted 4 200w Eco-Worthy panels in series, specs are:

Rated Power: 195W	Solar Cell: Monocrystalline
Maximum/Peak Voltage(Vmp): 18V	Open Circuit Voltage(Voc): 21.6V
Short circuit current: 10.83A	Maximum current: 11.89A

His cabin is more wooded than my shed, and gets a lot of partial shade, it might get full sun for maybe 2 hours a day, and he was running a SHITTY charger, I don't know what, but he said it was like $25 on ebay, charging a pair of lead acid batteries.

Well, today he called me, he went back to his place in early afternoon, it was filled with smoke, the chinese charge controller had BURNED UP and melted itself to the wall, melted his battery cables, and melted both his batteries. He did not have a breaker/fuse in between the panels and the charger, but I think what really screwed the pooch was most likely the voltage, as in series that would be 72V, and I'm guessing his cheap ass controller had a max input voltage of 24 or 50volts, I'm not sure.

In any event, everyone is okay, and I said I'd help him design a system that would be a lot safer. So after dealing with Renogy's bullshit, I'm going to push him towards a Victron system since I'm happy with mine, and the app/control has proved extremely beneficial in figuring out what was going on with my batteries, configuring things, monitoring them, etc. So, I mocked up 3 ways to use his panels, keep in mind, most of the time it is partially shaded:



He has no problem adding more wiring, so I was thinking his best bet was probably to run them all in parallel to combat the partial shade. However, he is running a 12v system, so maybe there's more of a benefit to run the hybrid/2 panels in series/parallel approach purely to get the voltage up about 12v earlier/later in the day?

Either way, it seems like a Victron smart charger with a 100V input would work for any of these, I was thinking a 100/30 or 100/50. Would a 100/30 really be limiting him that much? Also, what size breaker would he need going into the charger?

Thank you guys so much for the advice, I am definitely learning a lot and happy to report my system is still online and has been working great.

 

[sunshine_eggo]

I would attribute the downfall more likely to the installation or the device itself rather than the lack of fuses.

He has no problem adding more wiring, so I was thinking his best bet was probably to run them all in parallel to combat the partial shade. However, he is running a 12v system, so maybe there's more of a benefit to run the hybrid/2 panels in series/parallel approach purely to get the voltage up about 12v earlier/later in the day?

4P is probably best. Shading is ass. Downside is those are high current panels, and he'd need a combiner box with a fuse or breaker on each panel circuit as MC4 splitters are only good for 30A.

If a combiner box isn't an option, then 2S2P.

Either way, it seems like a Victron smart charger with a 100V input would work for any of these, I was thinking a 100/30 or 100/50. Would a 100/30 really be limiting him that much?

800W/14.5V = 55A, i.e., that's the minimum current needed to deliver 800W to the battery. 67A at 12V.


The 30 might be fine, but that's a 40%+ penalty. Given the conditions, I wouldn't risk missing out on any available power. 100/50 would be my preference.

Also, what size breaker would he need going into the charger?

1.25X the rating of the wire.

If he goes 4P, he needs a fuse/breaker on each panel in a combiner box. The panels have a maximum fuse size on the back. Use that.

If he goes 2S2P, he doesn't need anything between the PV and MPPT. The panels are essentially the fuses. You can put one on each string if you like.

There should be a fuse or breaker between the MPPT and the battery. Use 6awg minimum and fuse/breaker for 70A.

 

[SamDeleted]

I'm going to push him towards a Victron system since I'm happy with mine

Let's hope he has deep pockets lol.

There is plenty of good quality equipment out there that's doesn't come in a fancy blue box

 

[ShaneC]

Let's hope he has deep pockets lol.

There is plenty of good quality equipment out there that's doesn't come in a fancy blue box

Epever is highly rated and quite a bit cheaper. Remote monitoring can be DIYed if necessary but shouldn't really be needed once everything is up and running.

 

[Mattb4]

Your voltages should be Voc for panel arrangement consideration and not Vmp. Fro 12vDC battery system you most likely would be best with a 2S2P arrangement which will give some shading compensation.

 

[SamDeleted]

Epever is highly rated and quite a bit cheaper. Remote monitoring can be DIYed if necessary but shouldn't really be needed once everything is up and running.

Yea that's what I'd be going for if I was doing a little solar project like this guys cabin.... the monitoring software is more for fun than it is vital to making solar power

plus EPever MPPTs can take the mt50 monitor that costs £30~ .

 

[MichaelK]

What is your location's weather like? Wiring all four in series, the Voc at room temp is 86.4Voc. Just a few degrees below freezing, and the voltage will bump up past 100V. Use Midnight's string calculator if you want to find out exactly. https://www.midnitesolar.com/sizingTool/index.php

Most likely, with a 25$ price tag, the controller was a fake MPPT, or maybe just a PWM which he didn't know how to apply properly. As Matt mentions, 2S2P will be a safer configuration then redoing 4S1P. Otherwise, get a 150V charge controller.

Since the roof only gets 2 hours of clean sun per day, it might be more advantages to get even more panels, wire 5 or 6 in series, and then position them away from the cabin in the sunniest location you can get to. At 120+VDC, you can go 100+ feet with little or no voltage drop with 10 gauge solar cable. You will however, have to upgrade to a higher, 150V or 200V controller, which will cost more, but not extravagantly more. Here is another link to a voltage drop calculator, which will help you fine-tune your design. https://www.calculator.net/voltage-drop-calculator.html

 

[ADDvanced]

Let's hope he has deep pockets lol.

There is plenty of good quality equipment out there that's doesn't come in a fancy blue box

Like what? I'll consider anything except renogy.

 

[SamDeleted]

Like what? I'll consider anything except renogy.

Yes couldn't agree more

I am not in the US , I'm in Europe so not 100% on what's available over there. Hopefully someone more knowledgeable than me can help

But Epever make passable kit for the money. Also guessing he needs an inverter, not just DC loads , so how about a reasonably priced 'all in one' like this 24v MPP solar

2500w 24v MPP Solar inverter 80A MPPT solar charger high PV450V batteryless | eBay

Find many great new & used options and get the best deals for 2500w 24v MPP Solar inverter 80A MPPT solar charger high PV450V batteryless at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Edit: this is an EU model no good for you , but US version are available

 

[sunshine_eggo]

Yes couldn't agree more

I am not in the US , I'm in Europe so not 100% on what's available over there. Hopefully someone more knowledgeable than me can help

But Epever make passable kit for the money. Also guessing he needs an inverter, not just DC loads , so how about a reasonably priced 'all in one' like this 24v MPP solar

2500w 24v MPP Solar inverter 80A MPPT solar charger high PV450V batteryless | eBay

Find many great new & used options and get the best deals for 2500w 24v MPP Solar inverter 80A MPPT solar charger high PV450V batteryless at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Huge "BOOO!" on this recommendation. First, it's EU spec. Second, who wants their inverter gobbling 40W continuously?

 

[SamDeleted]

Huge "BOOO!" on this recommendation. First, it's EU spec. Second, who wants their inverter gobbling 40W continuously?

Hey like I said don't know much about electrics in the states but thank you for pointing that out .. what would you recommend?

 

[ADDvanced]

If he goes 4P, what size fuses need to be in the combiner box? How do you know this? I've searched everywhere on ecoworthy's site and no "max fuse rating" is shown anywhere which is annoying AF. Real lost about this, and the more I read the more I am amazed that this infromation is not available.

Because the combiner box is an added expense, I'm thinking about suggesting he go to 2S2P, just using a pair of splitters. But no fuses required at all? Really? He should at least get a breaker disconnect between the panels and the charger for safety of installing it and whatnot. What size would be appropriate?

 

[sunshine_eggo]

If he goes 4P, what size fuses need to be in the combiner box? How do you know this? I've searched everywhere on ecoworthy's site and no "max fuse rating" is shown anywhere which is annoying AF.

It's usually on the label on the panel.

If not, typically about 1.25X the Isc rating rounding up to the next convenient size (15A given the panel current is good).

Real lost about this, and the more I read the more I am amazed that this infromation is not available.

Because the combiner box is an added expense, I'm thinking about suggesting he go to 2S2P, just using a pair of splitters. But no fuses required at all? Really? He should at least get a breaker disconnect between the panels and the charger for safety of installing it and whatnot. What size would be appropriate?

Could use individual breakers in the combiner box, 15A.

 

[Rednecktek]

Huge "BOOO!" on this recommendation. First, it's EU spec. Second, who wants their inverter gobbling 40W continuously?

More panels and battery is a better value to me than the blue plastic. It's like the Apple Tax, I just refuse to pay more for the name.

 

[jamiegreen]

More panels and battery is a better value to me than the blue plastic. It's like the Apple Tax, I just refuse to pay more for the name.

More batteries and panels which would probably end up costing the same if not more than just buying some tidy equipment in the first place, just doesn't seem that logical to me.

As for Renogy.. they are a joke if you ask me, they aren't even cheap. I mean its literally just rebranded Alibaba junk with a huge mark-up.

MPP's are a little hefty on the consumption, I don't think they are bad units though, but I sure wouldn't want to rely on one too heavily, they have their places.

And honestly I don't think Victron is THAT expensive, but I think maybe this is a bit of a US/EU issue, I mean sure your paying a bit more than the usual Chinese stuff, but I never found it overly pricey, but then again I'm in the UK and paying EU prices. What I do know is my blue plastic (well aluminium actually) has been running for 10 years without fault. And the new Multiplus II's are pretty damn cheap for what they are.

 

[sunshine_eggo]

More panels and battery is a better value to me than the blue plastic. It's like the Apple Tax, I just refuse to pay more for the name.

I find that a little funny as this forum is rife with folks struggling with EG4, growatt and MPP Solar issues, oddities and inconsistent support.

It's way more than a name. I can call or text my dealer with questions. When he doesn't know, he reaches directly to Victron to get an answer. It's a 5 year warranty that actually means something. It's an obligation by the seller to provide competent support OR they're not a seller anymore. There's also an entire community that readily supports its users (not DIY Solar). Lastly, these devices are in active development and refinement with regular and easy firmware updates to fix issues and introduce new features by a company that gives a shit.

Last thing I want is to rely on equipment with a mediocre reputation while in a remote area.

Will I ever own a cheap AiO system? Probably for some fun project or something. Would I ever use it for something I count on? Nope. I'll take an expensive thing I can count on vs. a cheap thing that's a crapshoot any day.

 

[SamDeleted]

And the new Multiplus II's are pretty damn cheap for what they are.

£1500 for an inverter charger talk about cost of living crisis lol !

 

[JWLV]

If he got a charge controller off Ebay for $25, it is definitely NOT an MPPT controller no matter what the seller says. With PWM controllers, what you put into it is what you get out of it. So if he put in 4 panels in series, the controller is putting up to 72-volts out to the battery. That assumes the PWM controller can even handle 72 volts in the first place. And you are probably right that the controller burned up because he exceeded its max input voltage.

In regards to setting up a new system, I think any decent MPPT controller is all he needs. It doesn't have to be Victron. If this was for my own cabin, I'd wire the 4 panels in series and let the MPPT controller handle the rest. 2 hours of full sun isn't much any way. No matter how you wire it in series or parallel, you're not going to get much out of it.

 

[jamiegreen]

£1500 for an inverter charger talk about cost of living crisis lol !

Once you've bought 3 replacement knockoff MPP units in the same 10 years my Victron has been running it won't seem so bad

On a serious note though, energy bills in this country are so ridiculous, spending these amounts of money off grid don't take too long to "payback" in the sense of what it would have cost you in leccy bills.

 

[Rednecktek]

Paying a little more for a better quality is one thing, but when I can buy complete spares AND have money left over for lunch it just feels like a rip off.

Especially when there are other Tier-1 products that are just as tried and trued for less money.

Like I said, Apple Tax.

In other news, being used makes it a possibility, but I'd still want to see the specs on it before believing it. Although, I do have an EPEver 20a SCC that I'd sell cheap because I'm so disappointed in it. ?

 

[sunshine_eggo]

Paying a little more for a better quality is one thing, but when I can buy complete spares AND have money left over for lunch it just feels like a rip off.

Especially when there are other Tier-1 products that are just as tried and trued for less money.

Like?

 

[Rednecktek]

I'm very drunk right now but Samlex and Midnite come to mind.

*Dealing with ex-wife...

 

[SamDeleted]

Once you've bought 3 replacement knockoff MPP units in the same 10 years my Victron has been running it won't seem so bad

Yea it is true , there's a reason victron has such a good reputation. And if you've got the money at the time i can see why people would go for it

but for me on the other hand , I'm from up north so I'm tight as a ducks arse lol ... £1500 is a LOT of money.. Also not every project requires top notch kit

 

[OzSolar]

Dare I offer that building and maintaining your own off grid power system is pretty serious business and should be treated as such. A healthy budget can help overcome a lack of expertise but I'm not sure the converse is true. Poorly documented, cheap equipment with no support is pretty difficult to safely overcome for very long.

FWIW: I don't think you'll find a lot of people living off grid with no name 3rd tier equipment for more than 5 years. Buy once, cry once.

 

[jamiegreen]

but for me on the other hand , I'm right as a ducks arse lol ... £1500 is a LOT of money.. Also not every project requires top notch kit

I agree, not every project I'd want to spend that sort of money either. Project in the shed? AIO will do, power in the cabin (assuming its not lived in too often), or something to run alongside the grid, something cheaper will do, but not cheap enough that it'll burn it down! Off grid only source of power, no. And trust me, it hurt me to spend it ?