1st off-grid adventure — need charge controller advice

AC/DC said:

will need to mount to something, otherwise lay on the shelf

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Just cut some cement board to place on top of the shelf. Bonus fire resistance.
I recently learned that concrete does conduct slightly but I think you would be fine at these voltages.

Zwy said:

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.

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Oh man, you're tempting me! I love me some simplicity.. only issue is that it's 48V only and I'm on 24V, ugh..

ScrotusGobbleBottom said:

Just cut some cement board to place on top of the shelf. Bonus fire resistance.
I recently learned that concrete does conduct slightly but I think you would be fine at these voltages.

https://www.lowes.com/pd/DUROCK-Brand-0-25-in-x-36-in-x-60-in-Cement-Backer-Board/1000383885

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Would this to drill into and securely mount, or just as an insulation between the rack and components, which will mostly lay there?

AC/DC said:

Would this to drill into and securely mount, or just as an insulation between the rack and components, which will mostly lay there?

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I would consider it able to keep things where you want with < 10lbs weight and horizontal.

Will had a video recomending wall mounting concrete board but I am thinking he drilled into a stud behind it for the heavy stuff.
The concrete board I have used I wouldnt hang something over 20 lbs on it, not even with robust dry wall anchors.

AC/DC said:

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,

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If you parallel strings of different orientation, you will get lower peak current, more hours of operation. That's more kWh from same charge controller, and fewer hours of relying on battery so more power available at night.

If you do over-panel and have some clipping, that's only during best days and hours. When you can probably afford to let some kWh escape. Panels are cheap (mounting no so much), so overpaneling is a way to get more power during off season, and more power per day.

AC/DC said:

Oh man, you're tempting me! I love me some simplicity.. only issue is that it's 48V only and I'm on 24V, ugh..

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I didn't catch the 24V system. If you're thinking 48V down the line, then I would move to 48V now and use the 3000W 24V inverter for something else like a portable system.

So much capability with 48V.

Zwy said:

I didn't catch the 24V system. If you're thinking 48V down the line, then I would move to 48V now and use the 3000W 24V inverter for something else like a portable system.

So much capability with 48V.

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Yea I'm looking hard at 48V it's just a safety thing for now. If/when I build a proper, cased battery I'll feel safer, but right now I'm making my own out of large individual 12V bats and I have 10 year olds around. Also want to keep it low voltage on the battery side (where I expect to work on most on an ongoing basis, whereas the PV stuff is mostly one time setup then just disconnect/move around) for the time being while I develop good habits.

Now, it would also require a lot of $ upfront to get to use these panels that are just sitting there in my backyard (not the least of which is an inverter, which I'd want to go with split-phase right away to be able to provide 240V so I can L2 charge the EVs). Theoretically, could I hook up the inverter directly to the CC and use power w/o a battery during the day? Cuz I don't have a 48V battery right now (and would wait for another sale from EcoWorthy to pick up 2 more 12.8V 150Ah units).

What affordable split-phase 48V inverters shall I be looking at? Of course I'd love a 6000XP, and if I didn't have to buy two to get 240V, I'd eat the $1.5k cost right now. Is WZRELB any good? What else should I look at? Is there an all-in-one like the 6000XP that has a CC but also does 240V?

AC/DC said:

Yea I'm looking hard at 48V it's just a safety thing for now. If/when I build a proper, cased battery I'll feel safer, but right now I'm making my own out of large individual 12V bats and I have 10 year olds around. Also want to keep it low voltage on the battery side (where I expect to work on most on an ongoing basis, whereas the PV stuff is mostly one time setup then just disconnect/move around) for the time being while I develop good habits.

Now, it would also require a lot of $ upfront to get to use these panels that are just sitting there in my backyard (not the least of which is an inverter, which I'd want to go with split-phase right away to be able to provide 240V so I can L2 charge the EVs). Theoretically, could I hook up the inverter directly to the CC and use power w/o a battery during the day? Cuz I don't have a 48V battery right now (and would wait for another sale from EcoWorthy to pick up 2 more 12.8V 150Ah units).

What affordable split-phase 48V inverters shall I be looking at? Of course I'd love a 6000XP, and if I didn't have to buy two to get 240V, I'd eat the $1.5k cost right now. Is WZRELB any good? What else should I look at? Is there an all-in-one like the 6000XP that has a CC but also does 240V?

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6000XP is split phase with single unit

Brucey said:

6000XP is split phase with single unit

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So weird, I could have sworn that I saw that you needed two for 240 split. Thanks! Now there's some serious internal debating to be had.. Just a shame those panels are just sitting outside doing nothing while I contemplate a 48V system.

AC/DC said:

Yea I'm looking hard at 48V it's just a safety thing for now. If/when I build a proper, cased battery I'll feel safer, but right now I'm making my own out of large individual 12V bats and I have 10 year olds around. Also want to keep it low voltage on the battery side (where I expect to work on most on an ongoing basis, whereas the PV stuff is mostly one time setup then just disconnect/move around) for the time being while I develop good habits.

Now, it would also require a lot of $ upfront to get to use these panels that are just sitting there in my backyard (not the least of which is an inverter, which I'd want to go with split-phase right away to be able to provide 240V so I can L2 charge the EVs). Theoretically, could I hook up the inverter directly to the CC and use power w/o a battery during the day? Cuz I don't have a 48V battery right now (and would wait for another sale from EcoWorthy to pick up 2 more 12.8V 150Ah units).

What affordable split-phase 48V inverters shall I be looking at? Of course I'd love a 6000XP, and if I didn't have to buy two to get 240V, I'd eat the $1.5k cost right now. Is WZRELB any good? What else should I look at? Is there an all-in-one like the 6000XP that has a CC but also does 240V?

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The 10 Kw SRNE does split phase 240V. About the same price as the 6000XP, but it much larger and some members run the whole house off it.

The latest from Watts247, the NHX hybrid series might be a good choice. Some members have been testing this unit, it may have the glitches fixed from the previous Megarevo built inverters. The NHX is different hardware/software and interface.

ScrotusGobbleBottom said:

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

https://www.amazon.com/Circuit-Distribution-Protection-Waterproof-Way/dp/B09XJZR51G?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&psc=1&smid=AOAWBY89MKXUL

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What breaker do you recommend? I'm having a tough time finding one, HD/Lowes don't seem to have DC stuff and on Amazon I'm not finding UL-listed ones, just some that say CE. Hard to discern quality, money is not a huge factor at this stage, it's for safety so I'd rather get a good one that people here recommend.

While at it, what Class-T fuse do y'all recommend? Right now I'd probably be good with 200-300A (my bat is 150Ah but wouldn't mind having the ability to discharge above 1C for special surge situations).

ScrotusGobbleBottom said:

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.

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To be perfectly clear in my mind, this would only happen when positive is close to negative, correct? Such as when the wires in a circuit breaker, or the CC, are close, but not when I'm plugging/unplugging an MC4 that is energized anywhere in the system, as that would be on the same polarity.

AC/DC said:

What breaker do you recommend? I'm having a tough time finding one, HD/Lowes don't seem to have DC stuff and on Amazon I'm not finding UL-listed ones, just some that say CE. Hard to discern quality, money is not a huge factor at this stage, it's for safety so I'd rather get a good one that people here recommend.

While at it, what Class-T fuse do y'all recommend? Right now I'd probably be good with 200-300A (my bat is 150Ah but wouldn't mind having the ability to discharge above 1C for special surge situations).


To be perfectly clear in my mind, this would only happen when positive is close to negative, correct? Such as when the wires in a circuit breaker, or the CC, are close, but not when I'm plugging/unplugging an MC4 that is energized anywhere in the system, as that would be on the same polarity.

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If the solar circuit isn't interrupted you could get an arc when you disconnect the mc4 connector. So you would close the breaker/DC disconnect prior to doing work.

home depot wont be a good source for anything rated DC.

AC/DC said:

To be perfectly clear in my mind, this would only happen when positive is close to negative, correct?

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Not only then, also when disconnecting under load.

AC/DC said:

What breaker do you recommend?

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Hoping someone else can help here. Mine came with my combiner box.

AC/DC said:

but not when I'm plugging/unplugging an MC4 that is energized anywhere in the system, as that would be on the same polarity.

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It absolutely can when you disconnect a circuit under load aka charging you batteries.
MC4s would be energized by the sun OR panels wired in parallel. the solar charge controller would be the load.

If you have a pv disconnect switched off, then there is no load on the panels, and no arc will happen with a same polarity mc4

AC/DC said:

What breaker do you recommend? I'm having a tough time finding one, HD/Lowes don't seem to have DC stuff and on Amazon I'm not finding UL-listed ones, just some that say CE. Hard to discern quality, money is not a huge factor at this stage, it's for safety so I'd rather get a good one that people here recommend.

While at it, what Class-T fuse do y'all recommend? Right now I'd probably be good with 200-300A (my bat is 150Ah but wouldn't mind having the ability to discharge above 1C for special surge situations).


To be perfectly clear in my mind, this would only happen when positive is close to negative, correct? Such as when the wires in a circuit breaker, or the CC, are close, but not when I'm plugging/unplugging an MC4 that is energized anywhere in the system, as that would be on the same polarity.

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Stellavolta.com have many of the Midnite breakers and you can use Amazon pay to checkout.

AC/DC said:

What breaker do you recommend?

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Here is the line I used for my DC breakers


They are only CE rated not UL, but CE is not bad, just might not be as strict of abuse testing as UL. And I went with the 400 volt DC rated and my system will never see over 150 volt. They also have a 1,000 volt rated line if you go to a 400 volt series array. I was very surprised to see these fairly small breakers rated to 400 volts of DC while not being polarity sensitive. Many DC rated breakers wan the current going a specific direction as they use magnets to help blow any arc out of the switch gap. Since these don't car about polarity, they must use distance and a barrier to break the arc. I have only tried them out to 100 volts so far, and they turn off clean with no issue. I intentionally wanted ones that did not care about polarity for the 125 amps battery breakers as the current could be flowing either direction depending on if it is charging or discharging. I have 2 batteries and a breaker on each one. If the current is perfectly balance, that would be 250 amps, but my inverter will only ever pull about 140 amps and my max charge current only hits about 90 amps.

AC/DC said:

Yea I'm looking hard at 48V it's just a safety thing for now.

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There is not really much of a safety difference here. Yes, you can get a shock a little more easily at 48 volts, and I did get one off my system, but you really should be taking the same safety precautions. I got shocked while fixing a balance lead in my battery bank, my sweaty arm brushed a bus bar and I felt my whole arm tingle pretty hard. I always wear low voltage rubber gloves now when I am inside the battery cabinet. Had I been wearing long sleeves or the gloves I never would have felt a thing. With 24 volts, you are dealing with double the current, and that can be as big of an issue.

My dumb, basic rule of thumb is simple. Keep the normal steady long term current under 100 amps. So a 12 volt system is good up to 1,200 watts, 24 volts to 2,400 watts, and 48 volts to 4,800 watts. A short term load to double those is okay. Many people do push far higher, but for me, this works well. My system is "48 volts" but really 50 to 58 volts at the battery. I run all my house loads on it and I still rarely see it hit 100 amps. Right now my whole house is only using about 850 watts from the battery bank, and that's only about 15 amps with the battery at 56.4 volts. But when my Central A/C kicks on, I will see another 4,000 watts. If the microwave is also running, that is another 1,800 watts. It can add up fast.

Brucey said:

If the solar circuit isn't interrupted you could get an arc when you disconnect the mc4 connector. So you would close the breaker/DC disconnect prior to doing work.

Click to expand...

ScrotusGobbleBottom said:

Not only then, also when disconnecting under load.

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ScrotusGobbleBottom said:

It absolutely can when you disconnect a circuit under load aka charging you batteries.
MC4s would be energized by the sun OR panels wired in parallel. the solar charge controller would be the load.

If you have a pv disconnect switched off, then there is no load on the panels, and no arc will happen with a same polarity mc4

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Whoa, I'm so glad I asked. I am not 100% clear on how it happens, thanks guys! Def going for a breaker.

To confirm my understanding, while I'm 100% going for a breaker (hoping to order tonight), turning the CC off would be another way to disconnect the load, correct?

I guess I should also practice pulling those MC4s apart quick!

seneysolar said:

home depot wont be a good source for anything rated DC.

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Unfortunate. Any local chains (ha!) that carry DC stuff?

Brucey said:

Stellavolta.com have many of the Midnite breakers and you can use Amazon pay to checkout.

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Thanks, checking them out and adding them to my list of specialized, quality parts suppliers.

GXMnow said:

Here is the line I used for my DC breakers

https://www.amazon.com/12V-400V-Miniature-Circuit-Breakers-Optional/dp/B0B256HF2P

They are only CE rated not UL, but CE is not bad, just might not be as strict of abuse testing as UL. And I went with the 400 volt DC rated and my system will never see over 150 volt. They also have a 1,000 volt rated line if you go to a 400 volt series array. I was very surprised to see these fairly small breakers rated to 400 volts of DC while not being polarity sensitive. Many DC rated breakers wan the current going a specific direction as they use magnets to help blow any arc out of the switch gap. Since these don't car about polarity, they must use distance and a barrier to break the arc. I have only tried them out to 100 volts so far, and they turn off clean with no issue. I intentionally wanted ones that did not care about polarity for the 125 amps battery breakers as the current could be flowing either direction depending on if it is charging or discharging. I have 2 batteries and a breaker on each one. If the current is perfectly balance, that would be 250 amps, but my inverter will only ever pull about 140 amps and my max charge current only hits about 90 amps.

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Thanks, that's what I was actually eyeing — I was actually thinking of picking one of these up so it comes in a box already:
Tho it will require me to start putting my MC4 crimping to the test

I was looking at the 1000V/30A because I'm assuming it's overbuilt compared to the 400V/30A. Am I right in assuming that this, if ever tripped, would be tripped on current and not voltage? With the 6000XP, which pretty much looks like it will happen, I will string all my panels in 6S and push over 300V at min temp. For the time being, I'm getting a "starter" CC and will run my existing 24V system till all the other parts are in place, but it will allow to lay all the groundwork so when the 48V system is ready it's pretty much just reconfiguring the panels from 3S2P to 6S and not much else than switch input to new CC. Should I get the 400V/30A instead?

GXMnow said:

There is not really much of a safety difference here. Yes, you can get a shock a little more easily at 48 volts, and I did get one off my system, but you really should be taking the same safety precautions. I got shocked while fixing a balance lead in my battery bank, my sweaty arm brushed a bus bar and I felt my whole arm tingle pretty hard. I always wear low voltage rubber gloves now when I am inside the battery cabinet. Had I been wearing long sleeves or the gloves I never would have felt a thing. With 24 volts, you are dealing with double the current, and that can be as big of an issue.

My dumb, basic rule of thumb is simple. Keep the normal steady long term current under 100 amps. So a 12 volt system is good up to 1,200 watts, 24 volts to 2,400 watts, and 48 volts to 4,800 watts. A short term load to double those is okay. Many people do push far higher, but for me, this works well. My system is "48 volts" but really 50 to 58 volts at the battery. I run all my house loads on it and I still rarely see it hit 100 amps. Right now my whole house is only using about 850 watts from the battery bank, and that's only about 15 amps with the battery at 56.4 volts. But when my Central A/C kicks on, I will see another 4,000 watts. If the microwave is also running, that is another 1,800 watts. It can add up fast.

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Totally, and I also understand more now, I am already practicing "single hand"/"one hand behind back" so that in the event of a mistake, it doesn't go thru my entire body just thru a hand/etc.

What gloves are you using?

I found that the 1000V/30A seems to have some advantages:

It is DC-only and the Internal Spatial spec is listed as Bigger. Gonna pick one up.

There's also this
Which includes SPDs — is that something I need at this point? In the diagram there is a ground connection from the SPD, I don't currently have a ground for this project (unless connecting to the house ground would work — I'm assuming no, and I don't understand the implications).

AC/DC said:

What gloves are you using?

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Mine are over 20 years old. They are below the "Class 0" electricians gloves. Mine are probably rated to just 500 volts, but thy bend easy fo working on small stuff. These are about as close as I could find.


Those are for working on up to 750 volt DC and 300 volt AC

I just found these on Amazon. They would probably be great for what we do under 100 volts.

AC/DC said:

What breaker do you recommend? I'm having a tough time finding one, HD/Lowes don't seem to have DC stuff and on Amazon I'm not finding UL-listed ones, just some that say CE. Hard to discern quality, money is not a huge factor at this stage, it's for safety so I'd rather get a good one that people here recommend.

While at it, what Class-T fuse do y'all recommend? Right now I'd probably be good with 200-300A (my bat is 150Ah but wouldn't mind having the ability to discharge above 1C for special surge situations).

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I get mine with holder from Don Rowe. A larger bank such as 4 48V batteries in parallel, I use a 175A T Class on each battery.

AC/DC said:

To be perfectly clear in my mind, this would only happen when positive is close to negative, correct? Such as when the wires in a circuit breaker, or the CC, are close, but not when I'm plugging/unplugging an MC4 that is energized anywhere in the system, as that would be on the same polarity.

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To disconnect PV, use an IMO disconnect.

Zwy said:

To disconnect PV, use an IMO disconnect.

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Thanks, these look amazing! There is a highly educational video on the product page which I unfortunately can’t link (at least on mobile, will try on my workstation).

I’m having trouble reading the diagrams, here’s what I’m looking at:

I don’t understand the 1 & 2 versions, assuming the breaker is the part my arrow is pointing to in each diagram, I’m only seeing 2 poles. And I’m not understanding why they’re calling it 4 Poles. #1 looks like it’s connected in series, #2 is not clear to me from the diagram how that’s a drawing of a parallel setup. I’m just not getting where the 4 poles are when it shows 2 connections to the breaker, just like in the unlabeled 2 Pole version and the top? And then Max Number of Strings is 1 for all of them anyway..

I’ll be running 3S2P, the top “2 Poles” versions should be fine right? I’d just like to understand what I’m looking at in those diagrams, what I’m missing.

AC/DC said:

Thanks, these look amazing! There is a highly educational video on the product page which I unfortunately can’t link (at least on mobile, will try on my workstation).

I’m having trouble reading the diagrams, here’s what I’m looking at:
View attachment 207235
I don’t understand the 1 & 2 versions, assuming the breaker is the part my arrow is pointing to in each diagram, I’m only seeing 2 poles. And I’m not understanding why they’re calling it 4 Poles. #1 looks like it’s connected in series, #2 is not clear to me from the diagram how that’s a drawing of a parallel setup. I’m just not getting where the 4 poles are when it shows 2 connections to the breaker, just like in the unlabeled 2 Pole version and the top? And then Max Number of Strings is 1 for all of them anyway..

I’ll be running 3S2P, the top “2 Poles” versions should be fine right? I’d just like to understand what I’m looking at in those diagrams, what I’m missing.

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So for a single string you'd want the two pole version, for two strings the four pole version etc. I have a 4 pole clone version so I can disconnect two strings to two different sccs.

It may be simpler for you to get an mc4 version here: