Parallel wiring 600w

[Smtrill]

6 renogy 100w in parallel, wondering of my idea for wiring set up would be up to scratch. Would be fusing each panel with a 10amp fuse. Assuming they reach from panel to panel, can I use two three panel branch connectors to create two sets of +/- and then use a 2 panel branch connector to make the final two wires that go to solar extension cord (with 50amp circuit breaker before charge controller?) Thanks.

 

[exit8]

What are you connecting these panels to?

 

[sunshine]

Would be fusing each panel with a 10amp fuse.

Why?

 

[Smtrill]

What are you connecting these panels to?

The panels would connect to a 40a renogy mppt charge controller which feeds 2 200ah SOK lithium iron phosphate batteries. I know the battery bank is a bit big, I plan to wire an identical solar array through another charge controller if needed. For now my concern is if I am parallel wiring correctly and safely as renogy does not sell kits for bigger than 4 panels in parallel. Thanks for your reply.

 

[Smtrill]

Why?

Haha good question. I've seen people say that if a short circuit occurs in a panel the rest can backfeed and cause a thermal overload. Will briefly recommended this in a video for parallel connection so I was going by that. I believe the renogy kits come with these fuses. Id love to not buy them and save money if they are unnecessary. Thanks.

 

[chrisski]

For my six renogy 100 watt panels, I got a Midnite solar combiner. Because of DC wiring loss, I went with 3S2P instead of 6P, so both my strings have 10 amp circuit breakers. THe combiner box can take six separate strings.

On my four 100 watt portable panels, I made a combiner box out of a junction box, and a circuit breaker box out of a junction box.

The circuit breakers I got are built to be disconnected continuously under full load, so I can use them to trouble shoot strings, or if I store my RV, only turn one set of panels on. Becomes quite difficult to troubleshoot without some kind of switch.

I have the Roof Panel Combiner box with the breakers next to the battery, and I put the Portable panel combiner box and circuit breaker box on a fold out panel by the trailer. Makes set up and troubleshoot easy.

Why else? Could be code, but you’d have to spend $100s of dollars to get a current copy or search endlessly though google and hope its giving you the most current data.

Also just finished paying off my trailer, and the circuit breakers are not that much.

 

[Smtrill]

For my six renogy 100 watt panels, I got a Midnite solar combiner. Because of DC wiring loss, I went with 3S2P instead of 6P, so both my strings have 10 amp circuit breakers. THe combiner box can take six separate strings.

On my four 100 watt portable panels, I made a combiner box out of a junction box, and a circuit breaker box out of a junction box.

The circuit breakers I got are built to be disconnected continuously under full load, so I can use them to trouble shoot strings, or if I store my RV, only turn one set of panels on. Becomes quite difficult to troubleshoot without some kind of switch.

I have the Roof Panel Combiner box with the breakers next to the battery, and I put the Portable panel combiner box and circuit breaker box on a fold out panel by the trailer. Makes set up and troubleshoot easy.

Why else? Could be code, but you’d have to spend $100s of dollars to get a current copy or search endlessly though google and hope its giving you the most current data.

Also just finished paying off my trailer, and the circuit breakers are not that much.

Nice, for your 6 panel 3s2p what voltage does that get you? If I use your combiner box for my 6 panels in parallel that would mean 6 strings straight to the midnite combiner? I want a 12v array for my purposes since my panels will be just a few feet from the batteries, have shading issues and I already have a 12v inverter. Thanks for sharing your array that was helpful to see that as an option.

 

[Hedges]

Nice, for your 6 panel 3s2p what voltage does that get you? If I use your combiner box for my 6 panels in parallel that would mean 6 strings straight to the midnite combiner? I want a 12v array for my purposes since my panels will be just a few feet from the batteries, have shading issues and I already have a 12v inverter. Thanks for sharing your array that was helpful to see that as an option.

You can still do 3s2p or 6s1p. Just need an MPPT SCC that can handle the maximum Voc on a cold day.
No fuses needed for either of those, but disconnect is convenient. No combiner, just a "Y" cable for two strings.
Shading issues not a problem for 6s1p. Slight shading of one string probably not a problem for 3s2p, but if half of one string is shaded you lose the string.
If multiple orientations, all within one series string need to be same/similar orientation.
I like multiple strings of different orientations. When SCC (or grid-tie inverter in my case) is maxed out, this lowers the peak and spreads it out over time. If you have a battery, spreading out production reduces depth of cycling.

 

[chrisski]

I put my Midnight Combiner Box inside the RV

With the midnight solar combiner box, it’s designed to be placed outside in the vertical position. I did not like the idea of placing it horizontal on top of the roof, so I ran both strings inside. If you use the midnight solar combiner box, I recommend mounting it vertical outside if possible or inside. Inside might require you to run all six strings through the roof.

I made a combiner box and circuit breaker box out of IP65 or IP67 junction boxes, DIN Rails, a 60 amp solar combiner Gang Box that mounts on DIN Rails, and 10 amp circuit breakers. I have that mounted on a board for my portable panels. It’d be fine on a roof, except needing to go up on the roof to turn the circuit breaker on or off.

 

[sunshine]

renogy does not sell kits for bigger than 4 panels in parallel

The reason for this would be to limit the amps going through the pwm cc.
By limiting the amps Renogy reduces the failure rate of CCs
In renogy's case you can parallel as many kits as you like with each set of panels having its own pwm cc.
Or you can add more panels by pointing them so that they get the sun at different times so the amps through the CC is still low,

MPPT CCs are sold with Renogy's series kits. probably the one you are looking at, Best to follow the other posts and stay in series.
However there are numerous benefits in going with a 12v parallel setup but not with the MPPT CC from the Renogy series kit.

 

[Smtrill]

MPPT CCs are sold with Renogy's series kits. probably the one you are looking at, Best to follow the other posts and stay in series.
However there are numerous benefits in going with a 12v parallel setup but not with the MPPT CC from the Renogy series kit.

Why is that? My renogy 40amp mppt cc is rated for 100voc and should be able to handle the max amps of my panels (36ish combined in parallel) or so I thought. Even if it is slightly overpaneled I am very unlikely to get full current on my roof with shade issues, and am ok with some losses as long as it isn't dangerous.

I put my Midnight Combiner Box inside the RV
Inside might require you to run all six strings through

Six strings as in my 6s1p where every panel hooks a + and - wire to the combiner box? Just trying to visualize the wiring this way.

You can still do 3s2p or 6s1p. Just need an MPPT SCC that can handle the maximum Voc on a cold day.
No fuses needed for either of those, but disconnect is convenient. No combiner, just a "Y" cable for two strings.

I believe my 40a mppt renogy charge controller can more than handle the voc from the 6 100w panels in parallel? I thought voltage doesn't stack with parallel connection. No fuses or combiner, huh? When in your opinion do they become necessary? For a larger system?

You all rock I appreciate the help, beginner here in case it wasn't extremely obvious.

 

[Hedges]

I believe my 40a mppt renogy charge controller can more than handle the voc from the 6 100w panels in parallel? I thought voltage doesn't stack with parallel connection. No fuses or combiner, huh? When in your opinion do they become necessary? For a larger system?

I was referring to one series string of 6 panels, or parallel connection of two strings, each 3 panels in series. If only 1 or 2 in parallel, no need for fuses.
3 or more panels (or series strings) in parallel, then each needs a fuse or breaker. The reason is, if one string had a short circuit, or failed bypass diodes, the other two strings would both feed their current into it, exceeding it's capacity to carry the current.

Correct, voltage doesn't add when connected in parallel, just in series.

 

[chrisski]

You can look at the “max series fuse rating.” Renogy publishes that.
My panels are 15 amps max series.

Because they are around 6 amps each, anytime I have more than 2 I need a fuse.

My roof panels have two strings, which does not exceed 15 amps, so I don’t need a fuse. I chose to add a circuit breaker to each string because I want the SCC not powered up when I am away. My Victron SCC goes into bulk charge when the battery is disconnected but the panels are still attached.

 

[Smtrill]

Chrisski / Hedges that alleviated so much confusion for me. I have read through so many forums and could not distill that information. Renogy panels are also 15a max series fuse rating and around 6 amps. So in my case I will do a single breaker for convenient disconnect before the SCC and a fuse at each panel if doing 6s1p. 3s2p gives the same overall voltage as 6s1p, correct? I'm not accidentally doubling or tripling the voltage for a 12v battery bank if I do that? It seems like the voltage should triple under that connection per panel, still well under Voc max for my SCC but suited for 24v or even higher?

 

[chrisski]

. 3s2p gives the same overall voltage as 6s1p, correct? I'm not accidentally doubling or tripling the voltage for a 12v battery bank if I do that? I

3S2P does triple the voltage; however, i you look at the max input for your charge controller, if that is not exceeded, it will step it down to the 12 volt charging/float voltage Automatically. In my case, it’s 100 volts, so I could not hook all six panels up. In a cold environment, voltage out in the panels goes up, so my 18 VMP may actually put out more than 20, so that would exceed the VMP.

So in my case I will do a single breaker for convenient disconnect before the SCC and a fuse at each panel if doing 6s1p.

I think you meant all six in parallel, not all six in series. For parallel, a fuse for each panel would work with a properly rated breaker that can take constant on and off, like a 150 VDC midnitesolar breaker. If your charge controller is 100 volts VOC, than you’d not want to hook more than 4 panels to it if these panels put out around 18 volts.

The MPPT charge controller I have can take a max of 720 watts 12 volt or 1440 watts 24 volts. Doesn’t matter if its a 20 volt input at 36 amps, or 80 volt input at 9 amps, the charge controller will still put out 720 watts. It may be a little more efficient at 20 volts, than 80 volts, but not a lot.

 

[Smtrill]

3S2P does triple the voltage; however, i you look at the max input for your charge controller, if that is not exceeded, it will step it down to the 12 volt charging/float voltage Automatically. In my case, it’s 100 volts, so I could not hook all six panels up. In a cold environment, voltage out in the panels goes up, so my 18 VMP may actually put out more than 20, so that would exceed the VMP.

I think you meant all six in parallel, not all six in series. For parallel, a fuse for each panel would work with a properly rated breaker that can take constant on and off, like a 150 VDC midnitesolar breaker. If your charge controller is 100 volts VOC, than you’d not want to hook more than 4 panels to it if these panels put out around 18 volts.

The MPPT charge controller I have can take a max of 720 watts 12 volt or 1440 watts 24 volts. Doesn’t matter if its a 20 volt input at 36 amps, or 80 volt input at 9 amps, the charge controller will still put out 720 watts. It may be a little more efficient at 20 volts, than 80 volts, but not a lot.

Gotcha. Wow, I think I'm wrapping my head around it. So 3s2p I wouldn't need fuses or breaker box, just my disconnect before the controller for convenience. 22.5 Voc per panel is 67.5 for 3s2p, SCC can do 100v so I'd be good. Amps would be 5.29 per panel, so 10.6 total. As Hedges mentioned I can lower the peak current by angling each series array differently to avoid maxing out my 40amp controller and spread out the charging. (SCC rated 550w 12v or 1100 24v). Am I having delusions of grandeur or is this looking legit? Much gratitude.

 

[Hedges]

One or two strings, 6s1p or 3s2p, could just use a single switch or breaker to disconnect.

3 strings in parallel it is supposed to have 3 individual breakers/fuses. But with 6A from each string and 15A fuse rating according to the panel, if I was going to ignore code I wouldn't worry about it. One shorted panel would get 6 + 6 = 12A from the other two, which is less than 15A by enough that even 25% extra for unusual illumination conditions wouldn't exceed it.

Looking good, there is a madness to my method. I'm in the process of doing that with 600 Voc max strings having different orientations (several of them so all fused). They typically sit at 480 Voc under nominal conditions, 380 Vmp, and 2500W or so per string. The objective is to deliver more kWh/day under net-metering without exceeding maximum watts. AM Wh aren't worth any less than 2:00 PM Wh, so that's what I'm doing to get credits for 6:00 PM and later consumption at higher rates when I can't make much power.

 

[Smtrill]

I think I have learned what I needed for this part of the project, and so much more from you all. Can't thank you enough.

 

[Hedges]

22.5 Voc per panel is 67.5 for 3s2p, SCC can do 100v so I'd be good.

Yes, that's safe.
Enough headroom from 67.5V at 25C that it won't get as high as 100V even during a Siberian winter.
I add 16% to Voc for my location's record cold, and the temperature coefficient of my panels.
If your Voc had been 85V or higher, then maybe not enough margin for locations that freeze occasionally.
So your 3 panels in series is fine; 4 in series would not have been.

 

[Smtrill]

Thank you very much Hedges that is great to know. Best of luck with your enormous system, if you haven't finished it already! You must be using multiple large SCC/inverters?