does this look reasonable?

[justchillin]

Based on input/recommendations from members here in this forum, this is how I've layed out the DC side of things for my home build.

---four battery banks consisting of 4 x 12v/100ah Power Queen LifePo batteries = 48v/400ah each bank. Edit: 48v/100ah each bank (48v/400ah combined)
---1/0 welding wire tying batteries together in series, then through disconnects and 150a fuses, then to the 600a buss bars.
----from the two 600a buss bars, using 2/0 wire, all the way to the two 6000w inverters (EG4 6k XP)

--Victron Energy BMV712 shunt
---Victron isolation switches

Battery balancer on each bank, yes
Next time I will use 48v batteries, yes.
Plan system BEFORE buying material, yes.
I appreciate the lead on the Draw.IO program, yes.

Inverters are mounted and AC side of everything is finished.
Can I get this blessed?
TIA

 

[12VoltInstalls]

battery banks consisting of 4 x 12v/100ah Power Queen LifePo batteries = 48v/400ah each bank

That’s 48V = 100Ah

Also think you want 250A instead of 320A fuses.

 

[timselectric]

Why are the battery disconnects on the negative side?
Normally they are on the positive side, or preferably open both, positive and negative.

 

[justchillin]

Why are the battery disconnects on the negative side?
Normally they are on the positive side, or preferably open both, positive and negative.

An EE regular here said to install on the negative side.

 

[timselectric]

An EE regular here said to install on the negative side.

That would be odd.

 

[justchillin]

That’s 48V = 100Ah

Also think you want 250A instead of 320A fuses.

original post edited, you're correct, thanks.

On the fuses, the holders are rated for 320a, hence the mix up. I will use 250a fuses

 

[timselectric]

If you are only going to disconnect one side, it's better to do the positive.
This way, between the disconnect and the BMS, you can still actually completely isolate a battery from the system.

 

[justchillin]

That would be odd.

I had never seen it on the negative side but here's what he wrote: A cutoff switch per string would go on the negative side of the battery between it and the bus bar.
Perhaps I misunderstood

 

[rodrick]

I’ve seen it done in ag and auto and a big downfall is when someone installs something like a 2 way radio and grounds it directly to the frame and then try’s to start with the switch off those ground wire don’t work well cranking a engine

 

[Drizzt321]

You don't need fuses on the NEG side, just the POS side. I suppose it doesn't hurt?

Also you'll need a pre-charge circuit. Not sure if 1 per inverter, or 1 for the system is better.

You also probably should do a cut-off switch for each inverter, so you can take it out of service but still have the other one active if you need to do maintenance, replace it, whatever. And probably means each inverter is on it's own AC breaker for it's output.

Why have a 500A bus bar after the shunt? Shouldn't you get another 600a, to make everything in the system matching? You'd then be limited by that bus bar if you wanted to add a 3rd inverter.

The 320a fuse for each inverter, is that the manufacturer recommended size? If so good to go.

And yeah, I've never seen a disconnect on the NEG, always on the POS. Ultimately, in theory, it doesn't matter, since you need a complete circuit.

Also try as best you can to have same cable lengths going from NEG & POS to the inverters. Doesn't have to be down to the fraction of an inch, but it's best practice to get them as closely matched as is reasonable.

Also which shunt? Make sure it'll handle the current and any growth, so if it's a 500a shunt, know that you can't grow above that (including surge capacity), since you have 600a bus bars.

While Victron is pricier, their Lynx set of power in, combiners, etc can be kinda nice for organizing and wiring, to at least get all of the battery in all together, and then branch off from there. Plus they're 1000a so tons of headroom.

 

[justchillin]

Also you'll need a pre-charge circuit. Not sure if 1 per inverter, or 1 for the system is better.

this is new to me.......is that the lead pencil trick?

You also probably should do a cut-off switch for each inverter, so you can take it out of service but still have the other one active if you need to do maintenance, replace it, whatever. And probably means each inverter is on it's own AC breaker for it's output.

just ordered 2 disconnect switches, good call

Why have a 500A bus bar after the shunt? Shouldn't you get another 600a, to make everything in the system matching? You'd then be limited by that bus bar if you wanted to add a 3rd inverter.

500a should be more than enough. The 600s were just stupid cheap on EBay, overkill tho

Also try as best you can to have same cable lengths going from NEG & POS to the inverters. Doesn't have to be down to the fraction of an inch, but it's best practice to get them as closely matched as is reasonable.

yeah, I am being very particular on this one

Also which shunt? Make sure it'll handle the current and any growth, so if it's a 500a shunt, know that you can't grow above that (including surge capacity), since you have 600a bus bars.

Victron 712. It's rated for 500a

While Victron is pricier, their Lynx set of power in, combiners, etc can be kinda nice for organizing and wiring, to at least get all of the battery in all together, and then branch off from there. Plus they're 1000a so tons of headroom.

As anal as I am, I researched the shit outta the Lynx system ........for weeks to try to make it work. They are tidy and good looking. I just could not make it work in the end

And yeah, I've never seen a disconnect on the NEG, always on the POS. Ultimately, in theory, it doesn't matter, since you need a complete circuit.

this I'm still trying to understand. A disconnect stops a loop from completing so where it's placed shouldn't matter. Others have tried to explain but I can't wrap my head around it....yet

 

[Drizzt321]

this is new to me.......is that the lead pencil trick?

Probably? I don't know that exactly, but I can guess.

What is pre-charge and how it works

Sep 13, 2021

Easy way to pre-charge capacitive loads using the TAO BMS

• Philtao
• Beginners' Resources

Inverter Disconnect Switch with Precharge

Jun 4, 2020

Inverter Disconnect with Precharge

• FilterGuy
• Inverter's

As anal as I am, I researched the shit outta the Lynx system ........for weeks to try to make it work. They are tidy and good looking. I just could not make it work in the end

Yeah, Lynx as busbars are nice, or potentially using the Class-T version (you'd need 2 then, only 2 inputs) could be useful, but they do make for a pretty specific physical layout requirement.

 

[timselectric]

I had never seen it on the negative side but here's what he wrote: A cutoff switch per string would go on the negative side of the battery between it and the bus bar.
Perhaps I misunderstood

It's just odd. Which brings into question all of their advice.
While it's true that you can stop the flow of current from anywhere in the circuit.
You are going to spend the rest of your systems life explaining why you went that way. lol

 

[justchillin]

It's just odd. Which brings into question all of their advice.
While it's true that you can stop the flow of current from anywhere in the circuit.
You are going to spend the rest of your systems life explaining why you went that way. lol

fair enough. I signed up here to help me with my build. Not unlike the entirety of the dubyadubyadubya, opinions abound.
As to the explaining part, ain't my focus. Safety/function is.

Edit to add: my original post was to garnish insight. I'm not here to counter. Sometimes need to hear things twice to grasp, but hey, have our wives not already taught us that?

 

[timselectric]

fair enough. I signed up here to help me with my build. Not unlike the entirety of the dubyadubyadubya, opinions abound.
As to the explaining part, ain't my focus. Safety/function is.

Edit to add: my original post was to garnish insight. I'm not here to counter. Sometimes need to hear things twice to grasp, but hey, have our wives not already taught us that?

Understand completely.
My recommendation is always to disconnect all non grounded conductors. (Also a NEC requirement)
But many people do only switch the positive. (Definitely better than nothing)
Switching the negative will turn off the current flow. Even though it's not the standard. But, as long as you are the only person who will be working on your system, then I don't see any problem with it.

 

[12VoltInstalls]

Switching the negative will turn off the current flow. Even though it's not the standard. But, as long as you are the only person who will be working on your system, then I don't see any problem with it.

Obviously there is no argument against this statement.
Just for an example, however, of why disconnects on the pos(+) side are a better solution is my water heater circuit. Sometime ago but recently I was doing some work on the water system. I wanted to purge any air from the tankless system and I tried to pull the spade connector of the DC feeding the ignitor transformer. My fingers were wet/slippery and I couldn’t get the pos(-) so I just yanked the negative(-). I turned on the water and the flow switch still kicked on the burner.
Somewhere there is/was a second path to ground in the plumbing or propane lines- if I’d pulled(switched) the pos(+) it wouldn’t have ignited.
No harm was done but it was interesting.

But with batteries and solar cables etc. with so much potential- imagine if your were thinking you were disconnected and some equipment ground or something could still provide a path to ground and you crossed a contact with “a thousand amps” resulting over a 12ga wire or whatever- or a circuit board that runs on milliamps! - you just are better of keeping your pos(+) circuits exclusive and holy.

Just an observation. Murphy’s Law is real.

 

[Backyard]

How are you guys making out the wires with his black on black drawing? No contrast and it's so difficult to read anything

 

[timselectric]

How are you guys making out the wires with his black on black drawing? No contrast and it's so difficult to read anything

I see black and red, on white background.

 

[Backyard]

I see black and red, on white background.

I wonder if darkode on the website is messing with it for me

This is what I see

 

[Backyard]

I see black and red, on white background.

I wonder if darkode on the website is messing with it

This is what I see

 

[timselectric]

I wonder if darkode on the website is messing with it

This is what I see
View attachment 288122

Maybe

 

[doing it different]

I’ve seen it done in ag and auto and a big downfall is when someone installs something like a 2 way radio and grounds it directly to the frame and then try’s to start with the switch off those ground wire don’t work well cranking a engine

Belarus tractors use ground switch on the negative from the battery, as well as Cat equipment. I think JD excavators have a positive shutoff, that's controlled by the key.
Negative switching is not uncommon.
Most electronic circuits switch the negative side.

It probably has to do with what the engineer was trained with
conventional current flow theory or
electron flow theory.
Either way I naturally flip my brain back and forth. But do perfer switching positive. If you have a frame ground

 

[12VoltInstalls]

Most electronic circuits switch the negative side.

It probably has to do with what the engineer was trained with
conventional current flow theory or
electron flow theory

Probably because they use electronics ‘chassis’ as common negative(-) cuz it’s simple safe and easy
An observation I have made over the years- and it’s not a ‘rule,’ that I know of- is that two ‘conventions’ in boats, vehicles, RV’s, and motorcycles are frequently seen:
1) whatever means of wiring a circuit that allows using less wire/labor to manufacture the harness is what “they” use
2) in the negative ground DC systems I mentioned, things like ‘courtesy lights,’ certain older RV 12V lighting, etc., “they” switch the neg(-) because “they” use larger awg for the pos(+) and run short-length smaller awg to whatever neg(-) they can pick up or chain together (sounds like point 1 but it’s not specifically a ‘harness’)

This is why utility trailers, livestock trailers, and to a slightly lesser extent boats, older motorcycles and older RV trailers always seem to have impossible to figure out lighting failures- hardwired homeruns of neg(-) conductors on the ‘expensive’ trailers never have troubles.

Neither of it is a problem- switching pos(+) or neg(-) - as long as the source end of the non-common conductor is fused.

 

[doing it different]

Probably because they use electronics ‘chassis’ as common negative(-) cuz it’s simple safe and easy
An observation I have made over the years- and it’s not a ‘rule,’ that I know of- is that two ‘conventions’ in boats, vehicles, RV’s, and motorcycles are frequently seen:
1) whatever means of wiring a circuit that allows using less wire/labor to manufacture the harness is what “they” use
2) in the negative ground DC systems I mentioned, things like ‘courtesy lights,’ certain older RV 12V lighting, etc., “they” switch the neg(-) because “they” use larger awg for the pos(+) and run short-length smaller awg to whatever neg(-) they can pick up or chain together (sounds like point 1 but it’s not specifically a ‘harness’)

This is why utility trailers, livestock trailers, and to a slightly lesser extent boats, older motorcycles and older RV trailers always seem to have impossible to figure out lighting failures- hardwired homeruns of neg(-) conductors on the ‘expensive’ trailers never have troubles.

Neither of it is a problem- switching pos(+) or neg(-) - as long as the source end of the non-common conductor is fused.

I may be wrong. But I believe its because its easier or cheaper to make negative switching components....

Trailer lighting, always run a dedicated ground wire to your light, do not rely on frame ground. Solves alot of problems.
Also where ever possible use transport trailer lights with the rubber grommet style
Pack the plugs with grease and it will be trouble free.

 

[12VoltInstalls]

Trailer lighting, always run a dedicated ground wire to your light, do not rely on frame ground.

I spent a year employed at a utility trailer company. If it did anything for me it verified ideas I came up with over my 40+ year working/career life. You are 100%

Pack the plugs with grease and it will be trouble free

here in Vermont that merely delays the inevitable. #roadsaltinwinter

But I believe its because its easier or cheaper to make negative switching components....

I have seen evidence of that.
Manufacturing considers labor and materials costs, but switches are switches and wire is cost per length.