One more time, review my electrical plan?

[JDSquared]

Here's the plan with a couple of questions. I still need to label the wire sizes, I need to check the chart.

Question: Combiner box will actually be in the middle of the bus. Do I use the same wire chart for the wires from the panels to the box? Are there specific ires for the (is it MP4?) connections?

Question: Do I actually ground to chassis from the combiner box? The one I have saved shows three wires, but I thought I just went pos/neg to the controller

Question: Do I need more fuses? Is a cut off switch fine where I put it? What size fuse do I need at the Inverter? The docs say it has overcharge protection shutdown at 62.8V

Anything else look out of place?

I used a dash line for the shore power, because I am not 100% on what this inverter has. Says t can auto start a generator. So I am wau=iting to actually have it in my hands to finish that part.

Thank you all for helping

[JDSquared]

I am also unsure on the BMS. I ordered one, waiting I guess til mid July for it to show up. But it needs relays and a shunt and things. They were included, but not sure this will provide what I need. I am reexamining my options.

[dzl_]

What BMS did you purchase? And do you need one or two?

Originally Posted by JDSquared

Question: Combiner box will actually be in the middle of the bus. Do I use the same wire chart for the wires from the panels to the box? Are there specific wires for the (is it MP4?) connections?

I don't understand the question, can you rephrase it?

The connectors you are talking about are MC4 connectors.
There is special 'solar wire' I believe the only thing that makes it special is its UV resistance and rated for the harsh outdoors. Don't quote me on that though, there may be other differences.

Originally Posted by JDSquared

Question: Do I actually ground to chassis from the combiner box? The one I have saved shows three wires, but I thought I just went pos/neg to the controller

Sorry not sure. The documentation should clarify this.

Originally Posted by JDSquared

Question: Do I need more fuses? Is a cut off switch fine where I put it? What size fuse do I need at the Inverter? The docs say it has overcharge protection shutdown at 62.8V

Probably yes. I don't see a main battery fuse. I would have just a single + and single - connection going from your battery to your busbars and a main battery fuse on the + side, sized large enough to accommodate the maximum total current that will ever flow through it at one time, and small enough that it will blow before the rating of the wire is exceeded.

Then at every point (this is a generalization but mostly accurate) that you step down to a smaller size wire, you need a fuse near the beginning of the wire (the logical place is right off the + busbar). And again it needs to be sized larger than the max current that will flow through it, and smaller than the max current the wire can handle.

I hope this mostly makes sense, if it doesn't, or if I misunderstood anything, please let me know and I'll try to rephrase.

Here are a couple resources:
Fuse and Breaker Sizing and Placement
Intro to fuses and circuit breakers (video)

[JDSquared]

Originally Posted by dzl_

What BMS did you purchase? And do you need one or two?



I don't understand the question, can you rephrase it?

The connectors you are talking about are MC4 connectors.
There is special 'solar wire' I believe the only thing that makes it special is its UV resistance and rated for the harsh outdoors. Don't quote me on that though, there may be other differences.



Sorry not sure. The documentation should clarify this.



Probably yes. I don't see a main battery fuse. I would have just a single + and single - connection going from your battery to your busbars and a main battery fuse on the + side, sized large enough to accommodate the maximum total current that will ever flow through it at one time, and small enough that it will blow before the rating of the wire is exceeded.

Then at every point (this is a generalization but mostly accurate) that you step down to a smaller size wire, you need a fuse near the beginning of the wire (the logical place is right off the + busbar). And again it needs to be sized larger than the max current that will flow through it, and smaller than the max current the wire can handle.

I hope this mostly makes sense, if it doesn't, or if I misunderstood anything, please let me know and I'll try to rephrase.

Here are a couple resources:
Fuse and Breaker Sizing and Placement
Intro to fuses and circuit breakers (video)

I remembered about the mc4 after I posted. Added some wire to my cart.

And I forgot to add a fuse between the battery and the bus bar. Thank you. I guess I should add one before the DC converters as well. That would fuse everything.

I bought a chargery 16s BMS. I should only need the one. It should work but it looks like a pain to set up and program now that I watched a few videos of people doing that.

[JDSquared]

I'm on the road all day. I forgot to put bus bars on my shopping list I just. I'm just here reminding myself to do that when I get home.

[Doktari]

I would want a disconnect and overcurrent protection on the charge controller input. As it’s a 48 volt system you cannot use my favorite and inexpensive panel and breaker ( Sq. D Type QO) which would work great on a 12 or 24 system. The Midnite sola panels like the Quad or Baby are rated for higher voltage. One is a panel mount style breaker and the other a DIN mount style breaker.
I agree, I would add fuses to the DC converters.
PV wire is often double insulated.

[dzl_]

Originally Posted by JDSquared

And I forgot to add a fuse between the battery and the bus bar. Thank you. I guess I should add one before the DC converters as well. That would fuse everything.

I bought a chargery 16s BMS. I should only need the one. It should work but it looks like a pain to set up and program now that I watched a few videos of people doing that.

Yes, fuse the DC-DC converter circuits, and the inverter circuit if its smaller wire size than your main battery cable.


Chargery looks like a good BMS once you've got it all setup

[Doktari]

I’m curious about the Chargery BMS. I just ordered the Electrodacus BMS. I hope it comes with the right connectors, temp sensors, etc.
Let us know how the Chargery works for you.

[JDSquared]

Originally Posted by Doktari

I’m curious about the Chargery BMS. I just ordered the Electrodacus BMS. I hope it comes with the right connectors, temp sensors, etc.

Let us know how the Chargery works for you.

If I use it lol. I can get a different one before this finally shows up in July. I get impatient.

[JDSquared]

Originally Posted by dzl_

Yes, fuse the DC-DC converter circuits, and the inverter circuit if its smaller wire size than your main battery cable.


Chargery looks like a good BMS once you've got it all setup

Yeah I looked and the converter I ordered includes an online fuse. I think that's why I forgot it on my drawing.

[JDSquared]

Originally Posted by Doktari

I would want a disconnect and overcurrent protection on the charge controller input. As it’s a 48 volt system you cannot use my favorite and inexpensive panel and breaker ( Sq. D Type QO) which would work great on a 12 or 24 system. The Midnite sola panels like the Quad or Baby are rated for higher voltage. One is a panel mount style breaker and the other a DIN mount style breaker.
I agree, I would add fuses to the DC converters.
PV wire is often double insulated.

I worked all day and now my brain is tired. But you're talking about a cut off switch between the panels and the charge controller? I put one on my drawing between the controller and the battery.

I am trying to remember though, the charge controller needs to send the voltage somewhere right? So I should not cut it off after the controller.
And in my plan, each panel has a 12A breaker in the combiner box, I thought that would cover the controller.


But now I am all mixed up again about my cut off switch

[dzl_]

Originally Posted by JDSquared

Yeah I looked and the converter I ordered includes an online fuse. I think that's why I forgot it on my drawing.

This is good but still, the primary role of the fuse is to protect the wire, so even with a built in fuse (if this is what you meant by online fuse) in the inverter/charger, you'll want the wire to be protected either by your main battery fuse or by a fuse at the start of the inverter circuit. Does this make sense?

Originally Posted by JDSquared

I put one on my drawing between the controller and the battery.

I am trying to remember though, the charge controller needs to send the voltage somewhere right? So I should not cut it off after the controller.
And in my plan, each panel has a 12A breaker in the combiner box, I thought that would cover the controller.

A breaker is overcurrent protection and a disconnect switch all in one, so if you have breakers in the combiner box I think you are satisfying what Doktari is recommending.


As for your question about the disconnect switch between the battery and the charge controller. This is fine for a Victron Controller, there is no risk (it was once thought there was, but Victron has clarified that its not a problem) but I would switch out the disconnect switch for a circuit breaker (or keep the switch and add a fuse).

[JDSquared]

Originally Posted by dzl_

This is good but still, the primary role of the fuse is to protect the wire, so even with a built in fuse (if this is what you meant by online fuse) in the inverter/charger, you'll want the wire to be protected either by your main battery fuse or by a fuse at the start of the inverter circuit. Does this make sense?





A breaker is overcurrent protection and a disconnect switch all in one, so if you have breakers in the combiner box I think you are satisfying what Doktari is recommending.


As for your question about the disconnect switch between the battery and the charge controller. This is fine for a Victron Controller, there is no risk (it was once thought there was, but Victron has clarified that its not a problem) but I would switch out the disconnect switch for a circuit breaker (or keep the switch and add a fuse).

Online was a typo. Should be an IN-line fuse, in the positive wire. Can't see the size in the listing but I assume for now it's sized right, or documented what I need.

I am adding a breaker instead of a cut off switch. What I am trying to accomplish is just shutting everything off from the panels if something goes wrong so I have no new power coming in. If I want to work on something, or replace a panel etc. As I type it I think it needs to be between the panels and the controller. Maybe I should add one between the bus bar and the battery as well? I listed a fuse on my drawing, but a breaker might be better.

And my eyes aren't glazing over going through this stuff anymore lol.

[dzl_]

Originally Posted by JDSquared

Online was a typo. Should be an IN-line fuse, in the positive wire. Can't see the size in the listing but I assume for now it's sized right, or documented what I need.

I am adding a breaker instead of a cut off switch. What I am trying to accomplish is just shutting everything off from the panels if something goes wrong so I have no new power coming in. If I want to work on something, or replace a panel etc. As I type it I think it needs to be between the panels and the controller. Maybe I should add one between the bus bar and the battery as well? I listed a fuse on my drawing, but a breaker might be better.

And my eyes aren't glazing over going through this stuff anymore lol.

It sounds like you are on the right track, I'm having a hard time keeping track of the changes and additions/subtractions, I'll chime back in next time you update your diagram or if you have specifics you want to mull over

[Doktari]

If there’s plenty of space I like to have: 1). 15 amp breaker in combiner box for each panel, or 15 amp breaker in combiner box for each string of panels; 2). Input breaker for wire going to charge controller from combiner; 3). Output breaker for wire going from charge controller to battery.
This gives complete control and protection. But it’s a lot of panels and breakers. It’s how I learned from reading the Trace Engineering manual over and over. And vehicles dont always have the space.

[JDSquared]

My questions have to do with wire sizing. Or Amperage actually. Using the calculator is easy enough.

I added my disconnects to both sides of the charge controller.
I added my fuses at the battery terminal and before the Inverter and DC converter.

Started calculating wire sizes. I don't want to make this complicated, but I need to use enough words here to describe it and understand it.

A 72v from the panels to the controller 40amps max
B is the same but a shorter run.

No questions on these two. Unless this is wrong?

C and D from the battery to the inverter and DC step down

How many amps will my battery produce? These are used so I won't actually know the capacity until I test them and discharge them? Based on other reviews these should have between 3.2 and up to 4K of available storage each.

Dividing 8K by 48v is 166 Amps. Is that the number I use for a max? That jumps me up to a 2 AWG wire size, and that seems high based on all the others.

Also in regards to my DC step down. It's listed as 30A max. That's output right? 166 amps into this converter won't kill it if I understand this correctly.

So E seems easy. Adding the fuses gets me to 55 amps, but I won't get that even running everything. And the output from the converter is only 30A.


F is obvious as well, but I have one last question. If this is a 4000W inverter, at 120V, without accounting for losses, is that a maximum of 33.3 Amps output I can use at once? Might be less than I was planning. I would have to watch using the washer and AC and fridge all at once.

*Note. I plan to run AC on shore or generator, but in the off chance I am inside walmart and my dog needs the AC running while I am washing clothes and the fridge decides to cycle, this might become a problem?

Thanks for all your patience and input!

[JDSquared]

Oh and one more comment; I got my combiner box in the mail, and the ground wire is supposed to go to a high voltage lightning arrester. I hadn't even considered lightning to be a problem. But that's not a bad idea. Why have I not seen that discussed before?

[Doktari]

It’s shaping up. I wouldn’t use 2 gauge on a 4000 watt inverter even if it is 48 volt. But that’s just me. I oversize the wiring and cable. What does the manual say to use? Also I make both inverter cables the same length and twist them together.
I would not leave the washer going unattended. All three of those loads running would kill my batteries anyway.

[JDSquared]

Originally Posted by Doktari

It’s shaping up. I wouldn’t use 2 gauge on a 4000 watt inverter even if it is 48 volt. But that’s just me. I oversize the wiring and cable. What does the manual say to use? Also I make both inverter cables the same length and twist them together.

I would not leave the washer going unattended. All three of those loads running would kill my batteries anyway.

I didn't look to hard for a manual online yet. Should be here this week. Probably use the largest wire that fits.

Why twist the cables? I don't think I will have 13 inches of run from my battery so not much to twist together.

[dzl_]

Originally Posted by JDSquared

A 72v from the panels to the controller 40amps max
B is the same but a shorter run.

No questions on these two. Unless this is wrong?

I believe B is incorrect. B goes between the battery and the charger controller, it would be at the voltage of the battery and a higher current than A (max of 45A based on your charge controller).

C and D from the battery to the inverter and DC step down
How many amps will my battery produce?

The oversimplified answer is that the battery will produce only what the electrical device/circuit 'asks for' (this is technically incorrect, but conceptually useful I hope).

Batteries can push a shitload of amps, but they won't, unless there is a short circuit. Amps are a measure of current (flow rate), voltage is a measure of electrical pressure (a pushing force), pressure causes electricity to flow in a circuit. Resistance is what slows it down. This can be represented as Current = Voltage / Resistance. A battery is a voltage source, your batteries have 48 Volts of electrical pressure, the resistance comes from (1) the electrical devices/appliances (2) a tiny bit of resistance in the wire and the fuses and connectors. So amps are determined by the electrical pressure of the battery divided by the resistance of the devices being powered.

In short, don't worry about how many amps your batteries can produce, pay attention to how many amps your circuits require.

(Also, disregard battery capacity (amp-hours and watt-hours) when thinking about fuse sizes and wire size, its irrelevant).

Dividing 8K by 48v is 166 Amps. Is that the number I use for a max? That jumps me up to a 2 AWG wire size, and that seems high based on all the others.

Are we talking about C here? If so, its the max current (amps) in one direction (in or out) at a given time. In your situation that would be AC loads (4000W / 0.85 / battery voltage) + DC loads (30A).

Also I agree with Doktari, be conservative on wire and fuse size for C and D.

As for D, your inverter manual should have a recommendation for wire gauge and fuse size. I would follow that.

Also in regards to my DC step down. It's listed as 30A max. That's output right? 166 amps into this converter won't kill it if I understand this correctly.

Probably, but I would double check.
I'm not positive but I think 166A in would murder it if its not current limiting, but I think the above explanation illustrates why it won't actually have 166A as an input, unless you are using it wrong (by this I mean, its on you to make sure the devices on the 12v side never 'ask' for more than 30A combined, and if they do that you have properly sized fuses or breakers that will blow).

F is obvious as well, but I have one last question. If this is a 4000W inverter, at 120V, without accounting for losses, is that a maximum of 33.3 Amps output I can use at once?

Yes, I think you are thinking of this correctly here.

Might be less than I was planning. I would have to watch using the washer and AC and fridge all at once.

*Note. I plan to run AC on shore or generator, but in the off chance I am inside walmart and my dog needs the AC running while I am washing clothes and the fridge decides to cycle, this might become a problem?

The highly technical solution to this is, just don't do all that at once . Much easier and cheaper to adapt your habits/routine, than to oversize the system for off-chances that probably won't take much effort to avoid. So long as your inverter can handle the fridge + A/C simultaneously, it shouldn't be too hard to plan your clothes washing for times when you won't be running your A/C. That is my 2c at least.

I'm not an expert, and i make mistakes all the time, so if you or anyone else sees something that seems incorrect, unclear, or misleading bring it up.