Complete beginner here | Would like some feedback regarding a schematic before I purchase the components

[ThatCoolNerd]

I posted a schematic a couple of weeks ago and received some feedback. I've since made some adjustments and would like some feedback on this new one.

Basically I just want a little mobile power station that can power some stuff around the house and yard. Nothing crazy, maybe some fans and a computer in the summer. A small heater in the winter. An amplifier, periodically.

I understand I don't need OCP from the array to the solar charge controller if I don't have my panels in series, but I was still going to install a circuit breaker between them functionally as an "on-off" switch for my array. Does that work?

Are shunts necessary?

I'm going to purchase pre-made cables. I'd like to have mc4 quick-disconnects for my pv array, but we'll see.

I welcome any comments or concerns! Does this look safe?

I'm a little worried about the terminals breaking on the Victron charge controller. I've heard they're very flimsy and are easy to break for beginners like me. I kind of want to spend the extra $100 to get a 60A HQST charge controller just for the terminals, but I'm unsure.

P.S. I forgot to put it on the diagram but I was going to add a 40A T-class fuse on the positive wire from battery to inverter. Is that okay?

 

[Madco]

It looks fine.

A couple of points:

Per the NEC, you need to multiply your required conductor ampacities by 1.25 but your selected wire sizes are fine. It looks like you rounded to the next larger wire size!

Place your OCP devices as close to the battey as possible.

Be sure and use DC rated breakers.

The 40A MCB feeding the inverter may be too small to handle surges. Breakers are normally sized larger but it depends on the trip curves.

The class T fuse would be a nice addition but again, it might need to be larger given surge loads.

Hope this helps!

 

[Madco]

BTW, no shunts are necessary unless you want to measure power/energy.

 

[ThatCoolNerd]

Per the NEC, you need to multiply your required conductor ampacities by 1.25 but your selected wire sizes are fine. It looks like you rounded to the next larger wire size!

I thought I had already done that. Did I do it wrong? This is what I used:

600W / 48V = 12.5A
12.5A * 1.5 = 18.75A, rounded up for 20A DC-rated MCB

1200W / 48V = 25A
25A * 1.5 = 37.5A, rounded up for 40A DC-rated MCB (EDIT: See below realization, I think I'll need 70A DC-rated MCB)

Place your OCP devices as close to the battey as possible.

Will do. I'm assuming this is to minimize losses and have the OCPs trip more "accurately?"

The 40A MCB feeding the inverter may be too small to handle surges. Breakers are normally sized larger but it depends on the trip curves.

The class T fuse would be a nice addition but again, it might need to be larger given surge loads.

Good point! I had forgotten about that since I don't plan on pushing this little thing too hard.

Since the inverter I'm planning on purchasing has a 2200W surge, would the following be correct?

2200W / 48V = 45.833A
45.833A * 1.5 = 68.75A, rounded up for 70A DC-rated MCB?

Hope this helps!

It has, thank you!

 

[vallesj]

You need to consider the distances in order to select the cable. Drop voltage calculator online helps with that

 

[Madco]

YeA, it looks like you did factor in the 1.25. Guess I hadn't had my coffee yet!

The OCP location just protects as much wire as possible - doesn't impact trip accuracy.

I think the 70A MCB will be fine.

 

[Hedges]

The 40A MCB feeding the inverter may be too small to handle surges. Breakers are normally sized larger but it depends on the trip curves.

Surges fall within the time/current curve of fuse or breaker. No need to oversize for surge.

What is efficiency of inverter at full load? I'll assume 90%
What is low-voltage cutout? I'll assume 48V

1200W / 48V / 90% = 27.8A

Is circuit breaker thermal/magnetic (subject to nuisance trips) not magnetic hydraulic? Use standard 25% margin

27.8 x 1.25 = 34.7A

Current drawn from battery ripples with rectified 60 Hz sine wave, RMS current causing heating is 12% higher than mean current delivering power

34.7 x 1.12 = 38.9A

40A is perfect, with above assumptions.

 

[ThatCoolNerd]

You need to consider the distances in order to select the cable. Drop voltage calculator online helps with that

I'm planning on having this be a small mobile system. Everything will be very close together.

Surges fall within the time/current curve of fuse or breaker. No need to oversize for surge.

Gotcha.

Is circuit breaker thermal/magnetic (subject to nuisance trips) not magnetic hydraulic? Use standard 25% margin

How does one tell? Is it on the breaker itself? Or will it be in the specs on the manufacturer's website?

Current drawn from battery ripples with rectified 60 Hz sine wave, RMS current causing heating is 12% higher than mean current delivering power

Interesting! I will look into this.

 

[Hedges]

Specs will say what type breaker, and what trip curve which you can then find in additional manufacturer documentation.

The Square-D ones I use are thermal-magnetic.
Midnight/CBI and Midnight/Carling are magnetic-hydraulic.

Ripple Factor is my contribution to the art (that label may have been adopted to mean something slightly different in industry.)

But your 1.5 multiple was close to mine, which come to 1.4

Battery ripple current

After reading of someone tripping battery breakers at well below rating, I realized that could be due to pulses of current drawn by the inverter. Ideally capacitors would smooth out current draw so high frequency switching pulses and 60 Hz draw all came from the caps, and current from batteries...

diysolarforum.com

 

[ThatCoolNerd]

Specs will say what type breaker, and what trip curve which you can then find in additional manufacturer documentation.

The Square-D ones I use are thermal-magnetic.
Midnight/CBI and Midnight/Carling are magnetic-hydraulic.

I'm having trouble finding the distinction in any documentation.

I've been looking at CHINT and NADER brand DC MCBs, specifically, because that's what I've been seeing coming pre-installed with some of these server rack batteries. If I'm not mistaken, I think a NADER MCB comes installed on those massive EG4 PowerPro batteries. I figure if the companies manufacturing those server rack batteries trust those circuit breakers, then I do, too.

NB1-63 Miniature Circuit Breaker| chint global | CHINT

Functionprotection of circuits against short-circuit currents,protection of circuits against overload currents,switch,isolation.NB1 circuit-breakers are used in domestic installation, as well as in c...

chintglobal.com

NDB1-63 Series Miniature Circuit Breaker | Nader Circuit Breaker

I don't see any clear indication whether these products are thermal-magnetic or magnetic-hydraulic. I even dug into their respective user manuals.

Am I just looking in the wrong place?

I don't live in an area with too massive of a temperature differential, so in terms of performance they would probably both work similarly. I just need to tell which type they are so I can size them appropriately.

 

[Hedges]

The documents under your Chint link don't say what type.



Wire and connection resistance causing heating that affects thermal breakers.

These Midnight units are UL 1077 Supplementary Protectors

https://www.midnitesolar.com/productPhoto.php?product_ID=191&productCat_ID=16&sortOrder=9&act=p

Under [Documents] are some that say "Magnetic-Hydraulic"

https://www.midnitesolar.com/pdfs/cbi_MCB_QZ_specification.pdf

They're not UL 489 circuit breakers, which provide some greater level of protection (greater separation between input & output, not sure what else.)

https://library.e.abb.com/public/f866cb46b60143f29b1722c8a08c83f5/ABB%20Leaflet%20-%20UL489%20vs%20UL1077.pdf

This document says which CBI models are UL 489

https://www.midnitesolar.com/pdfs/Q-Series(1).pdf

Note the delay curves have a line for 105%, guaranteed not to trip below that. So can be used continuously at 100%.

 

[ThatCoolNerd]

Okay, I'm sorry for all the questions, but where the fuck can I actually buy these things?

It seems like the only MCBs that are readily available are ones that are popular DC-rated MCBs or just any random AC-rated MCB. I can find product specifications, but I can't find an actual SELLER.

I'm trying to find a 2-pole, 20A, hydraulic-magnetic, short-to-medium delay, up-to 100VDC, UL489-listed circuit breaker.

This is actually annoying the hell out of me. I've been looking for nearly an hour. No wonder so many layman blow their systems up or injure themselves. Even if a layman/hobbyist were to put the time and effort in to research all of these things, manufacturers do not make it easy for them to find or purchase their products.

EDIT: I think I've found a distributor. This shit is bonkers. I'm surprised they don't set up their own webstores for this. What a headache.

 

[Hedges]

CBI and Carling seem to be more difficult to find retail, except those relabeled by Midnight.

This might be what you're looking for.
Note that it is polarized, can't be relied on to interrupt higher currents at full voltage in reverse direction.

Product - MidNite Solar

MidNite Solar Product Page.

www.midnitesolar.com

 

[ThatCoolNerd]

CBI and Carling seem to be more difficult to find retail, except those relabeled by Midnight.

This might be what you're looking for.
Note that it is polarized, can't be relied on to interrupt higher currents at full voltage in reverse direction.

Product - MidNite Solar

MidNite Solar Product Page.

www.midnitesolar.com

That appears to be exactly what I need, but I still can't find a way to "add to cart" on that item. Does that website not actually SELL the circuit breakers? I'm appreciative that it lists a price, but I don't see where to click to actually BUY IT.

EDIT: Is this normal? Needing to buy shit to put in your system but not actually being able to source it?

 

[Hedges]

Hmm, a few things Midnight sells direct, but in quantity. Like surge arrestors by the dozen.

Current Connected and Stella Volta are a couple resellers. I found Stella Volta through their eBay listings.
I also Google part numbers together with the word "price"

Stellavolta.com

Stellavolta.com is an online superstore and authorized distributor for solar energy, wind power, portable power, and outdoor equipment. We help DIYers, solar installers, and preppers with their renewable energy systems.

www.stellavolta.com

MidNite Solar MNEPV Circuit Breakers – 600Vdc 15A~20A ~ Current Connected

The MidNite MNEPV 600V Breaker is good for high-voltage systems that need a two-pole breaker. With two versions, the 15A and 20A, these are ideal for any 600VDC system. Specifications: Width: 1 inch (26mm) Environmental Rating: Type 1 (Indoor) Listed for US & Canada Din Rail Mount 2-pole

www.currentconnected.com

"MNEPV20-600-2PP" price at DuckDuckGo

DuckDuckGo. Privacy, Simplified.

duckduckgo.com