First attempt at a wiring diagram for 48v system, opinions?

[HalfBaked]

I'm attempting to design and install an upgrade from my current, dying 12v offgrid system.
Sorry it's not very pretty to look at, and maybe oversimplified, but it's mine.
I need opinions, all are welcome.
Thanks for looking.

 

[Mattb4]

Without knowing all the particulars of the panel ratings, how you intend to connect them and length of run to your SSC (Nor its ratings), about the only opinion I can give is it looks OK.

Was there any question that you wanted answered?

 

[HalfBaked]

Thanks Mattb4!
I didn't include the paneling details because I am fairly confident in that side.
I was only wanting someone else to say it should not produce a fireball.
Thank you very much sir.

 

[HalfBaked]

Ok, I do have a question.
What's the best way to physically wire up a rack of 5 batteries in parallel? Straight, diagonal?

 

[MisterSandals]

Does your pv combiner box already have disconnect capabilities?
Perhaps just a drawing issue but connecting to the end battery of a parallel bank usually suboptimal balance-wise.

5 parallel:

Calculation of parallel string battery currents

Can your mathematical model confirm that wiring each battery to a common bus bar, using equal length cables to each battery, provides a balanced charge/discharge?

diysolarforum.com

 

[HalfBaked]

Thanks for your input MisterSandals. I'm still reading that link, but it seems to be referring to connecting the batteries directly to busbars running vertically on either side of the rack. The SOK rack doesn't have those. How would you proceed?

And yes, I can disconnect at the combiner box.

 

[MisterSandals]

referring to connecting the batteries directly to busbars running vertically on either side of the rack. The SOK rack doesn't have those. How would you proceed?

You need "something" connecting all 5 in parallel. Are you planning on using bars or wires?

If bars, as illustrated, connect to midpoints between 1 &2 and 4 & 5.
If wires where you cannot make midpoint connections, i would connect to cells 2 and 4 diagonally.

 

[MisterSandals]

Or using equal length wires to each battery and joining them:

Calculation of parallel string battery currents

My interpretation of all this: The goal is to have the exact same line resistance from each terminal to the common point where the load current is drawn. Is that correct? Andy For the "Posts" configuration, yes, the goal is to have the same cable resistance from each battery to the load points...

diysolarforum.com

 

[HalfBaked]

Or using equal length wires to each battery and joining them:

Calculation of parallel string battery currents

My interpretation of all this: The goal is to have the exact same line resistance from each terminal to the common point where the load current is drawn. Is that correct? Andy For the "Posts" configuration, yes, the goal is to have the same cable resistance from each battery to the load points...

diysolarforum.com

Ok, if this is the best route for my situation, I'm assuming those connection points would be something like 6-stud busbars?

 

[MisterSandals]

Ok, if this is the best route for my situation, I'm assuming those connection points would be something like 6-stud busbars?

Thats probably best.
In a pinch i might just bolt them all together with 2 on one end, main lead, then the other 3. Clean surfaces and nolox everywhere.

 

[HalfBaked]

Thank you very much for this.

 

[HalfBaked]

As per previous advice, here is an updated sketch.
Is this method correct, with 2 sets of bars?
Or would it be better to attach all the equipment to the same set, but larger, busbars?
Thanks!

 

[MisterSandals]

3kW array / 60A SCC = 50A
With a 50A breaker you may get nuisance trips.

1 set of bus bars or 2 sets kind of depends on physical layout and distances. With a single set of bus bars near the battery, what are the distances to the SCC and inverter? Are SCC and inverter close to eachother and a long distance to batteries?
Both will designs work but when pricing wires and the extra bus bars, maybe one design is a lot cheaper? Or significantly easier to implement?

For your TS-MPPT 60, you probably want the remote display as its the only way to know what's its doing. Not exactly cheap for what it is though. If did not buy this yet, i'd opt for a victron SCC that you can integrate with the MP-II.

 

[Brett V]

4/0 cables from the battery and 2/0 to the inverter is extreme overkill. With a 125 amp fuse, #2 is sufficient or go with 1/0 if its a really long run and you're leaving headroom for more solar.

 

[HalfBaked]

3kW array / 60A SCC = 50A
With a 50A breaker you may get nuisance trips.

Agreed. I was trying to stay within the battery manufacturer's charging limit, but I suppose that's not the purpose of the fuse, and that's the job of the SCC? What size and type is good for this breaker?

1 set of bus bars or 2 sets kind of depends on physical layout and distances. With a single set of bus bars near the battery, what are the distances to the SCC and inverter? Are SCC and inverter close to eachother and a long distance to batteries?
Both will designs work but when pricing wires and the extra bus bars, maybe one design is a lot cheaper? Or significantly easier to implement?

Ok, good to know. I will study the options, thanks.

For your TS-MPPT 60, you probably want the remote display as its the only way to know what's its doing. Not exactly cheap for what it is though. If did not buy this yet, i'd opt for a victron SCC that you can integrate with the MP-II

I already own the tsmppt60, and am happy with it. You can also get into its details from an onboard webpage it serves and change settings using MSview on a PC if you connect it to a router.

4/0 cables from the battery and 2/0 to the inverter is extreme overkill. With a 125 amp fuse, #2 is sufficient or go with 1/0 if its a really long run and you're leaving headroom for more solar.

Thanks for this, I certainly don't want to make things more expensive or difficult.