Nissan Leaf 48v Off-Grid Solar Project

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Also, just noticed that starting at the midpoint you are running the conduit along the beam, effectively limiting some some airflow., and at the bend it is touching insulation? (Not sure by the angle). I have no idea if that would be enough to cause temperature variations... However, it's a variable, and food for thought.
 
Fukuokian said:
Also, just noticed that starting at the midpoint you are running the conduit along the beam, effectively limiting some some airflow., and at the bend it is touching insulation? (Not sure by the angle). I have no idea if that would be enough to cause temperature variations... However, it's a variable, and food for thought.
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I can't scientifically make a claim that things get hotter as the current flows - I just observe that in my particular case, it seems that way but as was pointed out - conduit along a wood beam is different thermally than conduit with insulation on top of it.

But... there's nothing like actual data instead of trying to put my personal spin on the data. The system went into float before I could get max power/heat readings for today. So I went with Classic #3 conduit to measure for today. This is 2 x 6awg in 1" conduit (31a @ 98v) carrying 2617 watts of PV to the charge controller. Ambient under the house is 21C/70F
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Midpoint along conduit - 25C/77F - conduit along side the wooden beams.
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Just past the bend - 27C/81F - conduit a bit into the insulation.
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Up to 30.4C/87F at the control box about 15ft further on - just below the insulation.
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Modest 5C/10F rise, but still a rise.

When overplanneled and doing 40a+ along each pair of wires instead of 30a the temps are more pronounced.

Also 4 x 6awg in 1" conduit is hotter than 2 x 6awg (duh), even though it appears to me to be US 'code compliant' to do 4 x 6awg wires in 1" conduit but maybe not with 60C rating. It was the 60C rated wire comment that started me down this rabbit hole :)
 
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My 14mm2 (>6awg) arrived 👌 (rated to 60C 😢). Luckily I need some grounding wire for the SPD, which is compliant :) to code if I put it in conduit or... I could strip the insulation and use the bare wire, which is also compliant if it meets continuity and resistance specs. (basically don't damage it in the stripping process)

Note to me: Once I get it installed, I need to do some resistance testing for safety and code compliance.

As I got a lot of the wire (10m), I'll use some for grounding the array... probably strip off the insulation too. It's compliant in my area if stripped correctly; re: continuity and resistance.)
 
Fukuokian said:
Almost finished charging about half of the modules to bring them up to the same voltage as the other half. (91 total) Then I'll recheck all cell voltages, and parallel them in 7 stacks of 13; this will be the final balance.

So this is where I'm experimenting a bit... 😉

To keep costs down, I'm using 16mm2 braided copper flat wire to do the main parallel connections (pic below) and plain flat iron washers with green barley paper stuck to one side. This is to prevent contact corrosion from dissimilar metals (re iron and copper).

Each terminal bolt will have a washer between its head and the braided flat wire. the bolt will pass between the braids, then through a 26mm piece of the original leafs copper flat bar and then into the terminal on the battery module. I didn't want to just connect the braided flat wire directly to the terminal because the braiding is slightly uneven; by sandwiching the flat wire beween the washer and the copper, I can get significantly more surface/electrical contact. Sorry if this is hard to follow, I'll update with pictures when I start making the connections.

Anyhow, here are some pics of how I'm making the washers. (A paper hole punch works perfectly, as it allow me to 'find' the center hole by pressing down lightly until its in position, then I can punch it out. I do have to frequently clean out the sticky centers.)

View attachment 32557View attachment 32558View attachment 32559View attachment 32560View attachment 32561


Total cost, is around $50 usd for everything (300 25mm washers, barley paper & 7m of braided copper flat wire.)
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Did you end up with sandwiching the braided copper flat wire beween the washer and the original leafs copper bar?
Was there enough original leafs copper bars?
 
kje said:
Did you end up with sandwiching the braided copper flat wire beween the washer and the original leafs copper bar?
Was there enough original leafs copper bars?
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Yep! --> https://secondlifestorage.com/index...f-48v-off-grid-solar-project.12890/post-92613 I did have to cut some of the long bars to have enough! (scroll down in the link to see how I cut them. *warning* If you do this, make sure you've got eye/skin protection, as it produces a lot of flying bits of copper.)

I haven't seen anyone else do this (braided wire bus bars like I'm doing), so it's experimental (I'll be monitoring it closely, mostly checking for heat); but I think the design makes sense. I was originally worried about losing contact surface area because the braiding is not perfectly flat; however using the copper (~8cm lengths,) instead of making smaller rectangular copper washers, gives it a lot more surface contact area.

Also, I'll have at least three cross stack (serial) connections between each stack of 20 modules to help spread the load. Plus if one were to fail, there's still enough amp carrying capacity with just 2. (Note to self: need to double-check that I've accounted for the extra leaf battery I bought. <-- Duh! realized that the important thing is what the inverter will be pulling & what the charger will be pushing... 5000w inverter, but need to think about peak handling too. ).

However, there's probably about 800amps of potential for a free ride across the rainbow bridge if I touch the wrong things! (https://www.freepik.com/premium-vec...0-4278-b7b9-a59a959e6cf6&query=Electric+shock)
 
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Well I think I got my battery box sorted! 😁 I could find a refrigerated truck box (not the truck) that should do the trick. I was originally planning to build something, maybe cinderblock or concrete... however, I realized it will be cheaper and quicker in the long run to find something I can just drop in place. It's similar to the ones in the pictures... I'll pay about $230 usd, plus I need to rent a truck to haul it to it's final destination. +$50 and gas.

I want it outside, and not directly next to the house for safety(fire) purposes. It's aluminum, and already insulated. (I'm not expecting the cooling unit to work, but who knows. (There's also a side siding door on the left.)
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That would work great. And you could add backerboard for added fire protection. That's what it's called here in the US. Basically it's concrete sheets used a lot for showers and bathrooms. About 1-2cm thick or so and reinforced with fiber mesh to make strong enough to move around and secure stuff to it.
And/Or you could also line with plywood. Oddly wood can be an excellent fire retardant when treated properly. Notice, Plywood not OSB or particle board. Basically in extreme heat conditions the wood would char rapidly creating a protective layer of graphite that protects the rest of the structure. A battery fire would be very hot very quickly, so it would work in this situation. You could also pretreat the plywood with a blowtorch to give it a boost right off.

Getting premade structures for dirt cheap is always the way to go :)
 
Fukuokian said:
Well I think I got my battery box sorted! 😁 I could find a refrigerated truck box (not the truck) that should do the trick. I was originally planning to build something, maybe cinderblock or concrete... however, I realized it will be cheaper and quicker in the long run to find something I can just drop in place. It's similar to the ones in the pictures... I'll pay about $230 usd, plus I need to rent a truck to haul it to it's final destination. +$50 and gas.

I want it outside, and not directly next to the house for safety(fire) purposes. It's aluminum, and already insulated. (I'm not expecting the cooling unit to work, but who knows. (There's also a side siding door on the left.)
View attachment 33642View attachment 33643
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And... you can take it with you if you move or even use it for off-grid camping (for a month)!
 
It was an adventure, but managed to unload this, heavier than expected, refrigerated box. Pushed half of it off the truck then pondered how to get it out completely without scraping the other end or damaging the rental truck. 🤔💡

Ended up pushing it completely upright, then moved the truck and I could lower it. I still need to prep a flat base for it. Probably gravel and pavers.
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I was trying to decide the layout for connecting my 12 panels in 4 strings of 3. Physically the panels will be in 2 rows, with 7 in the top row, and under that, 5 panels. I want to optimize it so as to use the least amount of cable to run to the combiner box. Asking Grok, (Ai) the optimal layout, came up with an almost identical layout to my first guess. However, more importantly, I also asked for how much additional cable I'd need (extensions).

I'm not relying on its answer---I've ordered extra, cuz I know I'll use it somewhere down the line anyway. But, it's kinda cool that I could just give a simple description, along with a link to my panel specs to get an answer that should be 'in the ballpark.'

After getting an answer to my initial result, I realized that my (first) description of the combiner box being 2 meters below panel 9 might be misinterpretted. I was correct, I had to specify "from the bottom of the panel" as Grok used the middle of the panel, reducing the total wire requirements.

Anyhow, I've ordered 30m of black and 30m of red, and some mc4 connectors. Plus, it was cool that I could as for a graphical representation of the system with connection information... It gave me an ascii version, but that's fine (though my font shifted the connection to the CB to the left...
If I'd used a unispace font, it should be aligned.)
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Warning: Ideally, the wires (+ and - ), or at least the total circuit length for each of the 4 strings should be the same length to avoid having different voltages (from voltage drop). However, my string total circuit lengths are relatively short, so any voltage drop with having a slightly longer string circuit length will be negligible. YMMV, I've added this in case someone is planning their own system. If you've got longer runs, and/or significantly different lengths, you may have a problem with voltage drop. (i.e. My research says that an industry standard is <3% voltage drop for PV s is acceptable)
 
My arrays are about 30 & 50 feet to combiner boxs and from there about 150 feet to charge controllers. Array to combiners are 10awg and combiner to charge controllers are 6 awg (40a max). Have not tried to measure voltage drop but all seems to function well - I get reasonable power readings at the controllers consistent with panel specs.

Sounds like your distances are less than mine so I’m guessing you’ll be pleased!
 
OffGridInTheCity said:
My arrays are about 30 & 50 feet to combiner boxs and from there about 150 feet to charge controllers. Array to combiners are 10awg and combiner to charge controllers are 6 awg (40a max). Have not tried to measure voltage drop but all seems to function well - I get reasonable power readings at the controllers consistent with panel specs.

Sounds like your distances are less than mine so I’m guessing you’ll be pleased!
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Yeah, I'm trying to minimize wiring as much as possible. Copper prices have gone up a lot. 💸 I got a good deal on some 22mm2 (4awg) wire to run from the CB to my charger/inverter. My last purchase was wire for making the extensions from the panels to the CB. I can get away with 14awg (because it's silicone wire)... (It meets my specs with the required safety headroom)

Next thing is to finish the battery box... pouring a cement slab maybe at the end of this month. 😄
 
This video highlights a danger when using mc4 connectors (or clones thereof) from different manufacurers.

View: https://www.youtube.com/watch?v=43dh2M_hNJo

I'm doing continuity/resistance checks with my own connections, but am wondering how to check the panel to extension connections.

I could: - be aware of the force needed to make the connection... There should be resistance when they mate.
- check for heat at those connections when put in service.
- my cable connections are sealed on the panel side of the solar panel. (I respect this level of quality with my Aiko panels... makes them a waterproof and corrosion resistant connection.) So I would have to open the mc4 connector at the end of the panel supplied cable, use a multimeter at the wire to crimp end with the extension wire plugged in, and check continuity to the end of the extension. (I'd do this with the panel covered, and probably indoors too.)

I'm leaning towards testing 1 or two panels this last way, as general proof they work together. (...and do the previous things in the list with all the panels/connections.)

What would you do?
 
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Over the last 7 years, I've purchased MC4(s) about 5 times from AMZ mostly (I think). I used them built my own cables using 10AWG "PV wire" to run from panels to combiner boxes. I crimped "and soldered" the wires to the connectors. No trouble to date.

For problem detection....
I have 4 x 12panel arrays (48 panels total) and I have I have a good amount of baseline data over several years. Thus, I believe I could tell if one of the 12panel sub-arrays was underperforming as it would show significantly less power than the others - indicating a problem. It's unlikely they would all fail at the same time but even so, I have baseline data to compare current power levels vs the past.

Also, I use Midnite Classic 150s which have arc fault detection/protection on the PV wiring coming in which adds a bit of assurance that I'll have some notification if arcing starts.

Bottom line...
Things (including MC4s) have worked smoothly heading into year 8... so I've become 'at ease' over this topic but again, I did solder as well as crimp.
 
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OffGridInTheCity said:
Over the last 7 years, I've purchased MC4(s) about 5 times from AMZ mostly (I think). I used them built my own cables using 10AWG "PV wire" to run from panels to combiner boxes. I crimped "and soldered" the wires to the connectors. No trouble to date.

For problem detection....
I have 4 x 12panel arrays (48 panels total) and I have I have a good amount of baseline data over several years. Thus, I believe I could tell if one of the 12panel sub-arrays was underperforming as it would show significantly less power than the others - indicating a problem. It's unlikely they would all fail at the same time but even so, I have baseline data to compare current power levels vs the past.

Also, I use Midnite Classic 150s which have arc fault detection/protection on the PV wiring coming in which adds a bit of assurance that I'll have some notification if arcing starts.

Bottom line...
Things (including MC4s) have worked smoothly heading into year 8... so I've become 'at ease' over this topic but again, I did solder as well as crimp.
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Your mc4 connections have definitely passed the test of time. 👌

Around 3/4 into the video he talks about different mc4 manufacturers sometimes being incompatible... Or not able to make good connections. Which made me wonder 🤔 how to confirm my mc4 connections.

In your case your connections are solid, and the soldering adds stronger connectivity at the crimp. 👍. Did you do any continuity testing between the male and female mc4s when you first made the connections?
 
Fukuokian said:
Which made me wonder 🤔 how to confirm my mc4 connections.
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If you are making the terminal connections, you take the metal pins and slide them into the existing connectors. If it takes a little bit of force, you're good. If not, then probably don't use that connector. This is how I test mine to make sure they are good for mating. Too bad there aren't baby connectors born from this union so I didn't have to buy more.
 
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