diy solar

diy solar

1st off-grid adventure — need charge controller advice

A

AC/DC

New Member
Joined
Feb 23, 2024
Messages
59
Location
Dallas
I just purchased 6 x Q.PEAK DUO BLK ML-G10+/t [data sheet] and am a bit confused on what charge controller to get and how to configure them. If I'm reading things correctly, VOC is 45.20, with "at MPP" specs being 37.68V @ 10.48A. Right now I have a tiny 24.8V 150Ah battery and a 3000W inverter which is just my proof of concept setup, but I do have two long range Teslas which will be more than happy to store the energy produced during the day (although, in a highly inefficient manner at the moment thru a DC->120V conversion — end game is split phase 240V, but that's down the line).

Strings are how many are in series right? Most decent charge controllers want 100V+ correct? So 3 in series would would be 113V "at MPP", is this okay to be over (as long as you're not under, I'm assuming)? How would I use all 6? What charge controllers?

Considering that I'm very likely going to 48V as my next battery build, ideally a charge controller that would work at both 24V and 48V would be nice. BUT, if there is something cheap (read: not Victron prices) that will work now for my 24V system, and if y'all recommend the 48V charge controller be a dedicated 48V unit, I will consider something that is 24V only too. Reason I'm thinking this is because sometimes dedicated units (for my future 48V in particular, that is the one I care the most about, and where I will spend top dollar) are much better than units that support dual modes/voltages.

Hit me with some suggestions! I am not opposed to Victron from the getgo. What should I be looking at? What configuration for these panels? This will be ground mount while I play around with things for the time being. Ideally, minimizing wire gauge by doing series vs parallel as much as safely possible would be preferable as I have a longish run and since this is all mostly proof of concept, I don't want to spend a ton on cabling I may not use down the line.
 
AC/DC said:
I just purchased 6 x Q.PEAK DUO BLK ML-G10+/t [data sheet] and am a bit confused on what charge controller to get and how to configure them. If I'm reading things correctly, VOC is 45.20, with "at MPP" specs being 37.68V @ 10.48A. Right now I have a tiny 24.8V 150Ah battery and a 3000W inverter which is just my proof of concept setup, but I do have two long range Teslas which will be more than happy to store the energy produced during the day (although, in a highly inefficient manner at the moment thru a DC->120V conversion — end game is split phase 240V, but that's down the line).
Click to expand...

6x 395W = 2370W

2370W / 29V = 82A

So you'll want at least a 70-80A controller to prevent leaving much on the table.

AC/DC said:
Strings are how many are in series right? Most decent charge controllers want 100V+ correct? So 3 in series would would be 113V "at MPP", is this okay to be over (as long as you're not under, I'm assuming)? How would I use all 6? What charge controllers?
Click to expand...

Voc must be used, and there must be sufficient temperature margin as panel voltage INCREASES with lower temperature. You must NEVER exceed the controller Voltage limit under any circumstances.

A 2S3P array on a Victron 150/85 or a Outback FM-80 would be a good configuration.

AC/DC said:
Considering that I'm very likely going to 48V as my next battery build, ideally a charge controller that would work at both 24V and 48V would be nice. BUT, if there is something cheap (read: not Victron prices) that will work now for my 24V system, and if y'all recommend the 48V charge controller be a dedicated 48V unit, I will consider something that is 24V only too.
Click to expand...

Any that handle 48V will handle 24V. Check Victron prices. They cut prices recently and are reasonably competitive with Renogy, etc., when you consider the better warranty and product.

The controller @ 48V will be able to handle 2X the power than it did at 24V.
 
150/100 or 250/100 would give you max output in a silent passively cooled form factor. About $100 more for the 250V version but may let you run an additional panel or two per string and save you some on wiring.
 
sunshine_eggo said:
IMHO, these are a small step down from Victron, but I've been pretty impressed with my neighbor's FM-80's. If my giblets weren't already so deep into Victron (or are their giblets deep into me :unsure:?), I'd seriously consider FM-80s.
Click to expand...
Yes, slightly dated design (kinda like the Midnite Classics), but right now for the price... very attractive.

A 150/85 Victron is about $100 more, plus the $35 plug in display (if you want a display)

As @Brucey pointed out, you could jump to the 100A version. I think if already paying extra for the Victron, this makes sense.
 
Thanks guys! Followup questions:
1. Where can that deal be had on the FM-80? Will probably still go Victron, but would like to see it. NEVERMIND THIS, FOUND IT. Darn it, little blue box, you're so appealing! :)
1.1a Followup, I know the Victron system has some nice user interface. Does this have a decent one too? I really enjoy products which look at least somewhat modern, if not physically, in software (web/apps).

2. If I spend that type of money I might as well go 250/100.

3. Is MC4 or Terminals preferred, what is the consensus these days?

4. I have very little battery right now, just shy of 4kWh (probably a lot less usable — two EcoWorthy 12.8V 150Ah in series). I do have a 3000W (6kW surge) 24V inverter and big loads (Teslas), I would like to use most of the production during the day directly into the loads. I can currently only pull at about 1450W, plus losses that should be closer to 1550W, hopefully soon I'll be able to pull closer to 1900W, with losses that should be close to the output of the array under optimal conditions. [My very basic] Question is, if I hook MPPT to battery and inverter to battery, for lack of a better way of putting it, when inverter draws while MPPT charges, it will draw directly from MPPT and "bypass" the battery in a sense right?

Ideally I'd want to start the day with battery @ something like 20%, charge the Teslas (bypass battery as much as possible) while sun is out with extra energy being banked into battery, then when sun goes down drain the battery down to 15% or so (and let the low solar output bring it back to 20-30% ready for the next day).

sunshine_eggo said:
6x 395W = 2370W

2370W / 29V = 82A

So you'll want at least a 70-80A controller to prevent leaving much on the table.
Click to expand...
Got it, so amps on CC are amps out to battery, so my bat platform voltage is relevant (in this case, 24V platform). Therefore when I go to 48V, I will double my poWer, and ability to add more panels. Is there an amps in limit? Is it basically the amp spec at maximum voltage (48V platform)?

sunshine_eggo said:
Voc must be used, and there must be sufficient temperature margin as panel voltage INCREASES with lower temperature. You must NEVER exceed the controller Voltage limit under any circumstances.
Click to expand...
Got it, thanks.
sunshine_eggo said:
A 2S3P array on a Victron 150/85 or a Outback FM-80 would be a good configuration.
Click to expand...
In Solar Speak™, S=Series (just like in Battery Speak™) but String = Parallel, right? So in Solar Speak (as exemplified in Victron calculator), Series: 3 Strings: 2 would mean 3S2P right? Since I may consider the 250/100, no reason not to go higher voltage right? Any gotchas with "very high voltage"? The Victron calculator does indeed have my panels and, for fun, it looks like I could do a 5S with the 250/100, which would be 246.4V "PV max. voltage @ min. temperature" (thanks for bringing up the temperature tip!). Not that I would, but easily 3S, so 3S2P would be easy to do.

I wish the calculator would calculate Amps and cable gauge (yes, I can do by hand, but it already has the data..).

sunshine_eggo said:
Any that handle 48V will handle 24V. Check Victron prices. They cut prices recently and are reasonably competitive with Renogy, etc., when you consider the better warranty and product.
Click to expand...
Where shall I get one, Amazon or..? When possible I do prefer Amazon for initial issues/ease of return/replacement, but for longer term, for specialized equipment, I'd prefer someone who provides actual service. Or does it not matter? I know Victron is made in China just like all the others.
 
Last edited:
Current Connected is highly recommended by many and offer a 10 year warranty on Victron gear (double the regular 5 year).
 
Keep in mind, if you jump all the way to the Victron 250/100 youll end up spending close to double that Outback unit. I believe they go for around $615 vs $336.
 
AC/DC said:
Thanks guys! Followup questions:
1. Where can that deal be had on the FM-80? Will probably still go Victron, but would like to see it. NEVERMIND THIS, FOUND IT. Darn it, little blue box, you're so appealing! :)
1.1a Followup, I know the Victron system has some nice user interface. Does this have a decent one too? I really enjoy products which look at least somewhat modern, if not physically, in software (web/apps).

2. If I spend that type of money I might as well go 250/100.

3. Is MC4 or Terminals preferred, what is the consensus these days?

4. I have very little battery right now, just shy of 4kWh (probably a lot less usable — two EcoWorthy 12.8V 150Ah in series). I do have a 3000W (6kW surge) 24V inverter and big loads (Teslas), I would like to use most of the production during the day directly into the loads. I can currently only pull at about 1450W, plus losses that should be closer to 1550W, hopefully soon I'll be able to pull closer to 1900W, with losses that should be close to the output of the array under optimal conditions. [My very basic] Question is, if I hook MPPT to battery and inverter to battery, for lack of a better way of putting it, when inverter draws while MPPT charges, it will draw directly from MPPT and "bypass" the battery in a sense right?

Ideally I'd want to start the day with battery @ something like 20%, charge the Teslas (bypass battery as much as possible) while sun is out with extra energy being banked into battery, then when sun goes down drain the battery down to 15% or so (and let the low solar output bring it back to 20-30% ready for the next day).


Got it, so amps on CC are amps out to battery, so my bat platform voltage is relevant (in this case, 24V platform). Therefore when I go to 48V, I will double my poWer, and ability to add more panels. Is there an amps in limit? Is it basically the amp spec at maximum voltage (48V platform)?


Got it, thanks.

In Solar Speak™, S=Series (just like in Battery Speak™) but String = Parallel, right? So in Solar Speak (as exemplified in Victron calculator), Series: 3 Strings: 2 would mean 3S2P right? Since I may consider the 250/100, no reason not to go higher voltage right? Any gotchas with "very high voltage"? The Victron calculator does indeed have my panels and, for fun, it looks like I could do a 5S with the 250/100, which would be 246.4V "PV max. voltage @ min. temperature" (thanks for bringing up the temperature tip!). Not that I would, but easily 3S, so 3S2P would be easy to do.

I wish the calculator would calculate Amps and cable gauge (yes, I can do by hand, but it already has the data..).


Where shall I get one, Amazon or..? When possible I do prefer Amazon for initial issues/ease of return/replacement, but for longer term, for specialized equipment, I'd prefer someone who provides actual service. Or does it not matter? I know Victron is made in China just like all the others.
Click to expand...
Mc4 is generally limited to 30A, it's more common to see the "tr" (bare wire models)

Yes, power basically goes from solar to load, with excess going to battery (or pulling from battery if solar isn't sufficient).

Going to 48V does double your effective wattage per A of SCC output versus 24V.
 
AC/DC said:
Got it, so amps on CC are amps out to battery, so my bat platform voltage is relevant (in this case, 24V platform). Therefore when I go to 48V, I will double my poWer, and ability to add more panels. Is there an amps in limit? Is it basically the amp spec at maximum voltage (48V platform)?
Click to expand...

100A out, yes.

The input limit is squishy. The units have reverse polarity protection that shorts the PV input if you connect the panels backwards to protect the unit. This relay is good to 70A, so your array Isc must not exceed 70A (observed) UNLESS you never hook your array up backwards. If you're willing to forego reverse polarity protection, you can go apeshit!

Just NEVER exceed 250Voc and use your record low temperature to confirm you'll never get there.


AC/DC said:
Got it, thanks.

In Solar Speak™, S=Series (just like in Battery Speak™) but String = Parallel, right?
Click to expand...

S = series. A string is the single series of panels.
2S3P = three parallel strings of 2 panels in series.



AC/DC said:
So in Solar Speak (as exemplified in Victron calculator), Series: 3 Strings: 2 would mean 3S2P right? Since I may consider the 250/100, no reason not to go higher voltage right? Any gotchas with "very high voltage"? The Victron calculator does indeed have my panels and, for fun, it looks like I could do a 5S with the 250/100, which would be 246.4V "PV max. voltage @ min. temperature" (thanks for bringing up the temperature tip!). Not that I would, but easily 3S, so 3S2P would be easy to do.
Click to expand...

5S is too high. 4S with 45-50Voc panels. Since you have 6, 3S2P. I borked this my first time out and put 45Voc panels 3S on a 150V controller. Fortunately, I caught it before we got too cold and upgraded to the 250/100.
 
Brucey said:
Current Connected is highly recommended by many and offer a 10 year warranty on Victron gear (double the regular 5 year).
Click to expand...
CC doesn't seem to carry the 250/100, what's my next go-to? Shall I just get it from Amazon? UPDATE: I found it on the CC site. Looking at various other combinations that may work.

seneysolar said:
Keep in mind, if you jump all the way to the Victron 250/100 youll end up spending close to double that Outback unit. I believe they go for around $615 vs $336.
Click to expand...
That is a hard pill to swallow.. endgame I will eventually see myself going with something like a 6000XP or a 18kPV if I decide to stick with it, which makes me wonder if it's worth dropping so much on a Victron 250/100 (tho the FM-80 is not an apples-to-apples at only 150/80).

sunshine_eggo said:
100A out, yes.

The input limit is squishy. The units have reverse polarity protection that shorts the PV input if you connect the panels backwards to protect the unit. This relay is good to 70A, so your array Isc must not exceed 70A (observed) UNLESS you never hook your array up backwards. If you're willing to forego reverse polarity protection, you can go apeshit!
Click to expand...
Got it. Although, unless my solar Voltage would be lower than my battery Voltage when I eventually get to 48V bats, there wouldn't really be a case when there'd be higher amps coming in, right? And I wouldn't want to run it low voltage anyway, I hate thick cables.

sunshine_eggo said:
5S is too high. 4S with 45-50Voc panels. Since you have 6, 3S2P. I borked this my first time out and put 45Voc panels 3S on a 150V controller. Fortunately, I caught it before we got too cold and upgraded to the 250/100.
Click to expand...
5S 45.2Voc (my particular pane's spec) is only 226V, should be plenty of headroom on 250V CC, no? It seems like I'd be wasting quite a bit of headroom on the MPPT voltage limit. As a percentage tho it's no different than 45.2x3S=135.6V on a 150V CC, so I guess if you advise against it I should take notice. That's why you recommended 2S3P earlier right (for the 150/80 or FM-80 CC)?

I'm seeing the temperature as a potential factor. With these panels, using the Victron calculator I could run 5S to -15C/5F. It doesn't normally get that cold in Dallas, although Feb 16, 2021 is tied for 2nd all time low with -19C/-2F (that wasn't pretty, we had our power go out). So I guess that explains it.

Because I have 6 panels I'd def want to do 2 groups of 3 right now; down the line maybe 4S2P.

For my education, what does Vmpp mean and why is Voc used for CC V limit? I'm not debating it I just want to better understand it.

Another question — can you mix panels? Like if I add something else (since for 4S2P I need 8 panels and I only have 6 right now), as long as the Vmax is within the limit @ lowest recorded temp? Or do they need to be the same?

Cabling
So according to my calculations, these panels have an Isc of 11.02A, am I right that a 3S2P would be 135.6V@22.04A, requiring 10 AWG cables, which are rated to 30A? Any particular kind of cable? I saw some cheap ones on Amazon which are "tinned copper", <$80 for 100 ft 1 pair. Not looking to save a ton here, just want to know what the general wisdom is.

Since I'll be looking at a terminals MPPT, do I cut one end off? Just regular cut then strip as usual, and maybe twist? I know I also need to snug and fondle them.

How do I combine the two strings, are the combiners? How close do I need to obsess with the quality of such combiners before I send the power downstream over the long haul cable?

Thanks again guys!
 
Last edited:
AC/DC said:
only 226V, should be plenty of headroom on 250V CC, no?
Click to expand...
I would say that is too close. It is certainly not worth it given you probably wont lose anything besides another run of 10 awg
AC/DC said:
2 groups of 3 right now; down the line maybe 4S2P.
Click to expand...
Smart plan.
AC/DC said:
why is Voc used for CC V limit
Click to expand...
Because you will hit it on a cold mid morning and every single time your batteries are full with the sun out. Over voltage is the WORST thing you can do to a charge controller
AC/DC said:
Or do they need to be the same?
Click to expand...
I am pretty sure that them all being the same is the only way you wont be losing watts.
This is a long discussion and its late. If someone doesnt chime in, I let you know tomorrow.
AC/DC said:
I saw some cheap ones on Amazon which are "tinned copper"
Click to expand...
Just make sure they are solar rated 10awg. Solar rated means UV protected. If you are burying cable it might make sense to NOT use solar cable only in the buried part. Im sure that some here would disagree with me so there is that, just an option.

As far as cable, I am very glad that I purchased an MC4 crimper and the connectors/inserts. If you catch the solar bug like the rest of us here, you will be glad you bought it. Its not expensive. It enables you to have water tight splices with PV cable. Just got to make up some ends with the crimper.

I cant really imagine that you wont need a jumper at some point. Just get the crimper.
AC/DC said:
I know I also need to snug and fondle them.
Click to expand...
Excellent! Dont forget to snug again after some use. The heat from the first week of sun seems to loosen them up.


AC/DC said:
How do I combine the two strings, are the combiners? How close do I need to obsess with the quality of such combiners before I send the power downstream over the long haul cable?
Click to expand...
There are combiner boxes. Watts247.com has some good ones.

PV Combiner Boxes – Watts247 Wholesale

watts247.com watts247.com

I use one. I have 3 strings that I combine. Do not use those MC4 Y connectors that is usually trouble. Quality wise, I think the main thing to ensure is that it includes a properly rated DC mains breaker. That is simply the most important part. You will be using it to troubleshoot and for safety you dont want it to arc flash when you are trying to turn it off. :) You can also get a combiner box with a SPD or lightning arrest. These only work when properly grounded. Other than that they will have string fuses and probably some diodes to prevent backfeeding.
.
 
AC/DC said:
It seems like I'd be wasting quite a bit of headroom on the MPPT voltage limit. As a percentage tho it's no different than 45.2x3S=135.6V on a 150V CC, so I guess if you advise against it I should take notice.
Click to expand...

Learn from my mistakes.

AC/DC said:
That's why you recommended 2S3P earlier right (for the 150/80 or FM-80 CC)?
Click to expand...

Yes.

AC/DC said:
Because I have 6 panels I'd def want to do 2 groups of 3 right now; down the line maybe 4S2P.

For my education, what does Vmpp mean and why is Voc used for CC V limit? I'm not debating it I just want to better understand it.
Click to expand...

Voc is the voltage the array hits if there is no load. You might imagine this can never happen... until it does.

Vmp is the max power voltage...about 80% of Voc.

AC/DC said:
Another question — can you mix panels? Like if I add something else (since for 4S2P I need 8 panels and I only have 6 right now), as long as the Vmax is within the limit @ lowest recorded temp? Or do they need to be the same?
Click to expand...

For strings in parallel, Vmp needs to be close. Within about 10% should be okay. You will see a 5-10% penalty on your entire array.
For panels in a single string, they will operate at the current of the lowest rated panel. Put 2 10A panels in series with a 5A panel, and all three panels will be limited to 5A.
 
AC/DC said:
That is a hard pill to swallow.. endgame I will eventually see myself going with something like a 6000XP or a 18kPV if I decide to stick with it, which makes me wonder if it's worth dropping so much on a Victron 250/100 (tho the FM-80 is not an apples-to-apples at only 150/80)
Click to expand...
If that's your end goal/direction doesn't make sense to buy a 250/100 when that's nearly halfway to a 6000XP.
 
ScrotusGobbleBottom said:
I would say that is too close. It is certainly not worth it given you probably wont lose anything besides another run of 10 awg
Click to expand...
Been doing a ton of research since I typed that message (that's the problem when something becomes an obsession, I can't even sleep sometimes w/o getting the info to clarify things I'm not clear on!) and am now crystal clear. It's a shame that the panels I got are can exceed 50V at the lowest temperature in my location, but it is what it is.

ScrotusGobbleBottom said:
I am pretty sure that them all being the same is the only way you wont be losing watts.
This is a long discussion and its late. If someone doesnt chime in, I let you know tomorrow.
Click to expand...
I think I got it, and it's something I will deal with down the line at this point.

ScrotusGobbleBottom said:
Just make sure they are solar rated 10awg. Solar rated means UV protected. If you are burying cable it might make sense to NOT use solar cable only in the buried part. Im sure that some here would disagree with me so there is that, just an option.
Click to expand...
Won't be burying anything right now, as a matter of fact it will be strung up around the top of my wooden fence to my garage, for all to see! :)

ScrotusGobbleBottom said:
As far as cable, I am very glad that I purchased an MC4 crimper and the connectors/inserts. If you catch the solar bug like the rest of us here, you will be glad you bought it. Its not expensive. It enables you to have water tight splices with PV cable. Just got to make up some ends with the crimper.
Click to expand...
Can you link some crimpers/kits that work well, pref Amazon? I understand "the real" tool is like $700, def not looking to spend even 10% of that if possible. I saw some stuff super cheap like $20, just need some good recommendations. And connector kits too. Should I just order from Bogue and wait or is there quality to be found in Prime Shipping form?

ScrotusGobbleBottom said:
I cant really imagine that you wont need a jumper at some point. Just get the crimper.
Click to expand...
Yea, that's my thinking too.

ScrotusGobbleBottom said:
Excellent! Dont forget to snug again after some use. The heat from the first week of sun seems to loosen them up.
Click to expand...
So I kinda thought you were half joking. What exactly to you mean?

ALSO. In some video, I actually think it was Will's but forget which in particular, I saw him take the end that plugs into a unit like the CC I will get (with terminals), strip it, then.. do something like put some sort of end cap that seemed to bunch the end together very nicely. Then that crimped on tightly, and that was then inserter into the terminal. What was that, is it recommended? I would not at all mind that as an extra step as it both looked and seemed like a very pro thing to do.

ScrotusGobbleBottom said:
There are combiner boxes. Watts247.com has some good ones.
Click to expand...
Not seeing a simple 2-to-1 there, and the prices!

ScrotusGobbleBottom said:
I use one. I have 3 strings that I combine. Do not use those MC4 Y connectors that is usually trouble.
Click to expand...
Any reason for this? Since I'll only be doing 2P and the Isc on these is 11.02A, that'll be 22.04A, well under even 80% of a regular MC4 connector's 30A rating (and understand that there are MC4 connectors rated for more than 30A too). I was totally planning on keeping it simply on the strings side with 2 Y connectors and just run my 10 AWG back to the garage where all the magic will happen. THERE I need some proper stuff, what would I put there (to cover all the safety points) if I were to go this route? I'm not super clear on fuses and disconnects, I understand what each component does but am confused as to how to set it up, ideally if there's a product in a small box that I can just pass thru to have fuses and a disconnect, that would rock. Kinda like those combiner boxes, but not combining anything, just adding fuses in line and providing a disconnect.

ScrotusGobbleBottom said:
Quality wise, I think the main thing to ensure is that it includes a properly rated DC mains breaker. That is simply the most important part.
Click to expand...
Is this what I'm talking about above? Quick calculation, my 3S2P would be 150V (min temp-adjusted) 22.04A, what would I need for this?

ScrotusGobbleBottom said:
You will be using it to troubleshoot and for safety you dont want it to arc flash when you are trying to turn it off. :)
Click to expand...
Yea, I totally don't want that — when/how "would an arc flash when I turn it off" happen? Are you talking about just throwing the disconnect breaker off causing an arc flash? That is no bueno and now I'm scared.

ScrotusGobbleBottom said:
You can also get a combiner box with a SPD or lightning arrest. These only work when properly grounded. Other than that they will have string fuses and probably some diodes to prevent backfeeding.
Click to expand...
I won't have a ground available for this project, all I have is the house ground in/around the garage.

sunshine_eggo said:
For strings in parallel, Vmp needs to be close. Within about 10% should be okay. You will see a 5-10% penalty on your entire array.
For panels in a single string, they will operate at the current of the lowest rated panel. Put 2 10A panels in series with a 5A panel, and all three panels will be limited to 5A.
Click to expand...
Got it, so if/when, just make sure it's real close. Will cross that bridge when I get to it I guess, should be solid for now with 3S2P.

Brucey said:
If that's your end goal/direction doesn't make sense to buy a 250/100 when that's nearly halfway to a 6000XP.
Click to expand...
Well, mostly because the 6000XP is 48V only and I don't have any 48V gear right now, and even if I got one unit, it can't do 240V need 2 units for split phase, and that's $3k+ already. But yes, 240V will greatly increase my EV charging efficiency, even if at a relatively low power — low power L2 charging is max L1 power.. For the time being, L1 it will be, if I get a 5-20 connector I'll be able to do 16A, right now I can only do 12A :(

But the 250/100 is a pretty penny, thinking if something lesser would work. Because my array can technically put out 82A at 24V charge voltage (~29V), there's not a ton of choice.. unless I go to 48V and cut those charge amps in half, but then again I hit my head against the high per-panel voltage which is greater than 50V at min temp, and because Victron doesn't make a 200V unit, 150V could only handle 2S, while the 250V at least gives me the flexibility of up to 4S (although with my 6 panels it only makes sense to do 3S in 2P config). But yea, the price tag is hard to swallow. Still eyeballing that Outback hard 😳
 
AC/DC said:
What exactly to you mean?
Click to expand...
My experience: I ran 4 solar strings of 12 Ah to a combiner box. Used 8 awg to carry the 48 amps inside to my victron SCC. I tighten and pulled 4x and called it good.... Fast forward 3 months I was installing my 6000xp. I found the 8 awg wire was almost falling out of the pv input. This was probably moreso the heat coming from the SCC more so that the wire heating up but still, it happened. The SCC pv input had slight visible damage from arcing. The daily heating and cooling of the SCC or wire loosened up the connection.
AC/DC said:
sort of end cap
Click to expand...
Those are called ferrules. That are handy with stranded wire into compression fittings. My opinion is that I should be using them, since I have them, But I have not installed them yet.
AC/DC said:
disconnect breaker off causing an arc flash
Click to expand...
Can and does happen. DC arcing potential is much more persistent than AC. It is definitely something to consider when choosing breakers. It absolutely needs to clearly be DC rated. and rated past your PV highest voltage
ARCS are not just "fire" they are plasma. Some very hot stuff.
Per the video, it seems as if the DC arc at 100V has no problem sustaining an acr at 3/4 of an inch. Guess what? Most switches dont have 3/4 of an inch of separation. They have specific designs to quench the arc in a smaller space at a specific voltage.
AC/DC said:
when/how
Click to expand...
If you pulled 200 A DC thru a 100A AC rated switch, Bad things could happen. Im not sure of the specific thresholds for angry breakers or switches. Just make sure its properly rated.
AC/DC said:
small box that I can just pass thru to have fuses and a disconnect
Click to expand...
Thats what a combiner box does.
AC/DC said:
how "would an arc flash when I turn it off" happen
Click to expand...
Interrupting the travel of electrons of any nature has arc potential. Some tiny, some huge and everything in between.
AC/DC said:
2P
Click to expand...
You would be fine for 2P actually. Its just that 3P needs a fuse. Those Y connectors are handy for 2P but I wouldn't use them everywhere. I guess Im not sure why I feel so strongly against them. Perhaps I forgot something!
 
Last edited:
ScrotusGobbleBottom said:
You would be fine for 2P actually. Its just that 3P needs a fuse. Those Y connectors are handy for 2P but I wouldn't use them everywhere. I guess Im not sure why I feel so strongly against them. Perhaps I forgot something!
Click to expand...
Great info, thanks. To recap, are you saying that for 2P which will put me at 22A I'm good to just Y combine at the panels and send it to my "shack" (what's the term used here, where your equipment is?), which is my garage, and I don't need a fuse until I go 3P or above?

ScrotusGobbleBottom said:
Those are called ferrules. That are handy with stranded wire into compression fittings. My opinion is that I should be using them, since I have them, But I have not installed them yet.
Click to expand...
I'll research. Is standard solar-rated wire stranded or not? Def interested in these, looked really nice in the vid.

ScrotusGobbleBottom said:
Thats what a combiner box does.
Click to expand...
Right, but I'm trying not to use a combiner box since I'm gonna use Y connectors to combine the two strings at the panel end. I still want to get a disconnect, ideally in a little box, and if going thru all that trouble, if one were to come with a fuse, why not. So something just with disconnect and, optionally, fuses but no combining, does something like that exist or does it need to be DIY? Fuse optional but 100% want a disconnect.

Mounting Equipment to .. what?
I'm not an electrician and have never done anything to this level with electrical stuff. I have an engineering mindset and am not intimidated by the project, I just get stuck on some of the physical things. Like what do I mount all of these to, the MPPT, the disconnects, stuff from my battery? I see a lot of people using planks of wood? I don't have a truck (just a Model Y SUV), I can't carry very large board. Where do I learn about the physical part of building this stuff out somewhat neatly, and functionally sound?

Here's what I have RIGHT NOW which will be going in the garage:
  • a garage with some space; house panel is near location I plan to start this project, let's call it the "you may end up sleeping on the couch, or worse" project
  • two (2) EcoWorthy 12.8V 150Ah batteries, connected in series for 25.6V 150Ah
  • a 3000W 24V inverter
  • a bunch of AC chargers that do not need to live in the garage
  • a DEWALT 3-Tier Steel Storage Unit (50" x 48" x 18") — Will showcased this unit in at least one video
So, already, I'm rather concerned that the Dewalt is made out of steel and I have .. electrical components with exposed terminals. The batteries are fine, they are blocky and heavy and terminals are toward the top. Inverter is fine too, posts are covered, but.. it will be resting on the steel shelving.. is this an issue?

Stuff to come and for me to figure out:
  • battery disconnect — have the switch, haven't yet installed. it is the type of switch that can mount in a hole
  • battery monitor — already have it, it has a shunt, ideally this is not hanging in the air? what/how do I mount it..
  • CC, either Victron 250/100 or Outback or something. with the Victron at least, looking at it, I'd be VERY uncomfortable having it on the steel shelf, as the terminals are at the bottom and according to what @ScrotusGobbleBottom said about 8 awg wires almost falling out, BIG BOOM could happen.
  • PV disconnect box/mechanism, will need to mount to something, otherwise lay on the shelf? hopefully I can buy a kit which comes as an insulated plastic box, so while not pretty, laying on the steel shelf would at least be an option, at least to start
  • stuff that I'm missing
So I want to at least have a gameplan in my mind as to how to set this up. Because I haven't done this kind of stuff before, it's a big stumbling block, I need to figure out what I need to source and how it will go together, if not exactly at least the overall idea.
 
I would just use the EG4 MPPT, all panels in series, 10AWG wire and watch the watts roll in. I run a pair with 8 530W panels on each one.

This would easily handle your 6 panels. Cost is $399 plus shipping.
 
AC/DC said:
don't need a fuse until I go 3P or above
Click to expand...
Correct Think of it this way. A solar panel can take a short circuit of its own power all day and not complain. In 2P it would take double its own, and in 3P it could take triple. Thats my understanding. Solar panels get angry with triple their rated short circuit current.
AC/DC said:
Is standard solar-rated wire stranded or not
Click to expand...
PV wire is always stranded "out in the wind" Any time a conductor has high frequency of moving, you use stranded.
AC/DC said:
So something just with disconnect and, optionally, fuses but no combining, does something like that exist or does it need to be DIY
Click to expand...

yes, a properly rated DC circuit breaker would be your "fuse" and disconnect. You can mount it to a din rail on the wall all by itself. or in a din box

AC/DC said:
physical part of building this stuff out somewhat neatly, and functionally sound?
Click to expand...
This very much depends on what your are mounting too and the weights of everything. I mounted my 6000xp on my basement wall, all other things are mounted in a wood cabinet with some of my batteries. I have positive and negative bus separated by a full wood divider in the cabinet with my shunt. This is where the 6000xps inclusion of breakers really shines. No extra wire, no extra mounts.
AC/DC said:
according to what @ScrotusGobbleBottom said about 8 awg wires almost falling out, BIG BOOM could happen
Click to expand...
and remember, the pv line CANT be fused to trip on overcurrent because your always aiming for max. Its the wrong place for a fuse.
You could put a DC AFCI on there to detect arcs tho.
 
You must log in or register to reply here.

Similar threads

T
Total novice, need some guidance for small system
Replies
8
Views
207
TFoil
T
driftin_crone
Charge controller help
Replies
1
Views
90
sunshine_eggo
sunshine_eggo
C
Newbie alert simple question about Voc on PVs.
Replies
7
Views
421
cyberfed
C
O
Solar Charge Controller Question
Replies
8
Views
460
pollenface
pollenface
5
Can charge my battery bank with 24v and use with 12v old inverter?
Replies
11
Views
263
mikefitz
mikefitz

diy solar

diy solar
Back
Top