Nissan Leaf 48v Off-Grid Solar Project

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I had an idea, to avoid an mc4 connection point... I'll probably use 1/2 an empty mc4 plastic housing at the bottom of the combiner box (no metal pin/tube in it). I can feed the wire through it, and tighten the mc4 housing to seal the wire entry. (see pic below) The wire will have a ferrule at the end to go into that string's circuit breaker. (Probably only works with my 14awg, or 12awg as long as it's od--with insulation--is less than 5mm.)

Note: I checked that the locking mechanism for the pin doesn't damage my wire... I'm not sure if they're all designed the same or not, or if that might be a problem with 12awg... something to check if anyone decides to do this too.

I don't see any issues with my situation... just have to make sure to connect the circuit breaker end first, then the other end to the solar panel. 😜
I'm using ferrule collars (without a plastic guard), so the wire should still be able to be pulled through mc4 housing if I want to remove it later. Also, I'll be using conduit to go from the combiner box to underneath the solar panels. (It'll act as a guard to prevent the wire from being accidentally pulled, and provide extra UV protection. I guess silicone has natural UV resistance, but the wire I bought isn't specifically labelled as UV resistant so I need to use the conduit to be compliant.)

I may cut off part of the mc4 bottom part in the picture to... or better yet turn in upside down from how it is in the picture. That way no one would think i just have a pin stuffed in it without the housing.

The blue line is the metal bottom of the combiner box.
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Fukuokian said:
Did you do any continuity testing between the male and female mc4s when you first made the connections?
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As @Korishan says you handle the connectors when assembling the wire -> connectors and in this process I looked at them to ensure they 'looked' the right size - but that's all. I agree with @Korishan that all mine 'sort of snapped in' when assembling them.

And since then, I've not had any issues so I can only assume that the various random purchases on AMZ are compatible because they work OK.
 
Fukuokian said:
I had an idea, to avoid an mc4 connection point... I'll probably use 1/2 an empty mc4 plastic housing at the bottom of the combiner box (no metal pin/tube in it). I can feed the wire through it, and tighten the mc4 housing to seal the wire entry. (see pic below)
Click to expand...
I didn't bother with MC4s at my combiner boxes, I just ran the wires directly to the breakers within the box. At the ground array combiner box, used rubber grometts to protect wires as they enter the combiner box. For the roof array, it's conduit from roof to a metal trough to combiner boxes.
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TMI:
For the roof, I ran each 3s string down to it's own breaker in the combiner box - e.g. 4 breakers (8 wires) per combiner box. That's why there's 2 x combiner boxes for the 24 panels on the roof. This gives 'fine grain' control as I can turn each 3s string on/off while standing on the ground.

For the ground array, I used Y-MC4s and combined 3s strings into 3s2p before entering the combiner box - this results in 1/2 the wire-pairs + breakers compared to the roof array and I only needed 1 combiner box. I can easily reach everything (all panels/wires) on the ground array so less incentive to do individual breakers.
 
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OffGridInTheCity said:
it's conduit from roof to a metal trough to combiner boxes
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Thanks for posting the pics! 😃 (The conduit run is very useful for me, as I need to run mine over the roof edge in a similar way.)

Is that Rigid conduit in the 2nd pic? (not emt right?) It looks very beefy!

There's no mistaking your shutoff switches... wow, they're big! 😲 ...I like em! (y) Are they repurposed from something?
 
Fukuokian said:
Thanks for posting the pics! 😃 (The conduit run is very useful for me, as I need to run mine over the roof edge in a similar way.)

Is that Rigid conduit in the 2nd pic? (not emt right?) It looks very beefy!
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It's 'metal' conduit w/water-proof connectors, not sure about rigid vs emt. The conduit is affixed to the mounting rails to steady it on the roof end. Going over the gutters avoids roof penetration and doesn't interfere with the gutter.
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Fukuokian said:
There's no mistaking your shutoff switches... wow, they're big! 😲 ...I like em! (y) Are they repurposed from something?
Click to expand...
That's the standard Midnite 6 breaker combiner box with multi-breaker on/off handle - https://www.solar-electric.com/mndico.html It's really just a box with midnite combiner box with 'group breaker toggle handle' option as apposed to the regular flat metal cover. The red handle moves plastic on the inside that fits over the breaker toggle levers and lets you turn all the breakers on/off at the same time using the red handle.
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This provides the 'quick disconnect' at the arrays that is required by my jurisdiction - otherwise I would have just done a flat lid.

Here's a showing 'just the box' (with flat lid). They come in 3, 6, or 12 breaker sizes - https://www.currentconnected.com/product/midnite-solar-mnpv3-mnpv6-mnpv12-combiner-breaker-box/ It's only the 6 breaker size that has the 'red handle' option I think.
 
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I needed to make custom solar mounting brackets for my Japanese tile roof. You might be able to buy them if your roof allows it, but in my case the rise between my roof decking and the space between the tiles is too small. Here's an example of some of the ones you can buy:

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Also, they're expensive (at least here). ($13-16 usd each) I need 20 so I put on my Macgyver hat and bought a bunch of these standard 90deg brackets (bottom of this picture below) and figured out how to bend them without an expensive brake press.

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The top metal strapping is the template I made by pulling off a tile and bending it to the dimensions I need. Then I made a bulky, poorly designed bender (🫣 which I'm not too proud of, but it worked for bending the 4 brackets I needed for my orginal 2 solar panels.)

Here's my new and improved diy brake press build... 🥳

1st, I repurposed a bench press adjustable safety catcher.

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Then off to the hardware store for < $6 usd in metal parts and screws. Using some scrap wood I built this guillotine looking contraption. The flat metal is sandwiched and bolted between two pieces of scrap angle iron I had. I ran the side pieces of wood through a table saw to make cuts to act as guides. I made the bottom piece of wood with two 45degree cuts on the table saw and fitted the 90degree metal piece and screwed it in.


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I added two guides and a spacer to hold the bracket for the first bend.

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Then a 5Ton bottle jack does all the work.

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I can turn the bracket around and do the second bend from the opposite side.
 
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I missed the timing for a smooth control joint and cutting the edges. But, it's good enough for who/what it's for. 😜
(Most of it is covered by the box.)
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Now I'm just waiting for the pad to finish curing, then it's time to install the battery box and batteries.

It's only my second cement pour, but I've learned a lot. This time I pre-measured the cement/sand/gravel and water.
Highly recommend doing this, as it saves time and possible mistakes.
 
Fukuokian said:
I needed to make custom solar mounting brackets for my Japanese tile roof. You might be able to buy them if your roof allows it, but in my case the rise between my roof decking and the space between the tiles is too small. Here's an example of some of the ones you can buy:

View attachment 33707View attachment 33706
Also, they're expensive (at least here). ($13-16 usd each) I need 20 so I put on my Macgyver hat and bought a bunch of these standard 90deg brackets (bottom of this picture below) and figured out how to bend them without an expensive brake press.

I can turn the bracket around and do the second bend from the opposite side.
Click to expand...
Fantastic work! I have a flat cement tile roof and used the Solar Roof hooks - https://unirac.com/product/solarhooks/ - this one in particular
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The bottom part lets one slide left or right to hit the truss but yet keep the upper part where you want it - was useful in a one or 2 placements.

What I love about this type of system (buy or build) with tiles is: there's no penetration of the roof material like you get in shingles and even replacing tiles (if needed) won't require taking these up. They can truly be a one and done.

I'm sure you don't need my tips :) just to share details... I used 3 5/8 LedgerLOK screws (thru felt -> truss) and was advised to screw them at an angle toward the truss instead of straight down as it increases the chances of biting into the stud. Used a grinder to cut shallow grooves under the tiles where they overlap so they lay flat over the horizontal part of the roof hook.
 
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Fukuokian said:
View attachment 33715


View attachment 33716

I missed the timing for a smooth control joint and cutting the edges. But, it's good enough for who/what it's for. 😜
(Most of it is covered by the box.)
View attachment 33717

Now I'm just waiting for the pad to finish curing, then it's time to install the battery box and batteries.

It's only my second cement pour, but I've learned a lot. This time I pre-measured the cement/sand/gravel and water.
Highly recommend doing this, as it saves time and possible mistakes.
Click to expand...
Very good work! 😊

I buildt the brackets from angle brackets in the hardware store:

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Necessity is the mother of invention 😎
 
OffGridInTheCity said:
I used 3 5/8 LedgerLOK screws (thru felt -> truss) and was advised to screw them at an angle toward the truss instead of straight down as it increases the chances of biting into the stud. Used a grinder to cut shallow grooves under the tiles where they overlap so they lay flat over the horizontal part of the roof hook.
Click to expand...
Yes, the 'screw angle' tip is good!

One other extra tip is to put a bead of silicone or roofing tar on the underside of the top tile, especially if you're in a windy or hurricane area. (Probably really only need to do the lower brackets that have more exposure.
 
Ok... kje is looking into heating his battery modules using the pads included with some leaf packs. I'm basically in the same boat and thinking about how I'll handle heating my batteries in cold weather. From my research 26 degrees is the optimal temperature for these gen2 leaf modules. So, in a perfect world if you can keep the batteries at that temperature (heating in the winter and cooling in the summer) you'll optimize your powerwall/bank longevity.

I was thinking about using a sand battery to store heat via a heating element powered by solar panels during the day, and then letting the sand release the heat during the night. I was running calculation through AI to see if this would be practical, and came across a ready-made, better solution called vehicle-mounted solar TES (Thermal Energy Storage.) Flower-Delivery trucks in Hokkaido (Northern Japan) use this and it's a well-proven system using +18 °C or +25 °C PCM (phase change material) panels. A similar system is used for tropical-fish & coral transport vans from Okinawa to Honshu (Main Japanese 'island') using +25–28 °C PCM.

So basically solar heat is collected during the day which melts the +18 °C or +25 °C PCM, these keep the refrigerated box at between15–28 °C all night without any grid power. This is an ideal solution for me, as I already have the insulated refrigerated box (minus the hvac unit). However, I have to see if it's economically feasible, as the pcm can be expensive. Next step is to see if I can source them in bulk cheap enough to warrant this system. Based on estimates, I'd need 250-300kg of the PCM at $2/kg for industrial bulk purchases would be $500-600usd.

So is it worth it? As I already have a couple of solar panels, mppt, wiring and even extra 24v batteries (from my soon to be upgraded solar power system) it looks like it's a yes for me, especially if I can source the PCM cheaper (used material, etc...)
 
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Also found a cheap diy way to make the pcm yourself, using 70% paraffin and 30% coconut oil... this brings the paraffin to a final melting point of 24.5 - 26 °C. I put in a RFQ (request for quote) to see what a bulk purchase (250-300kg) of paraffin will cost from a supplier.

Using this paraffin/coconut oil recipe:
Hokkaido flower-delivery kei-truck owners (2022–2025, daily winter use) 1,200 – 1,800 cycles 3–5 winters, still working perfectly, no visible separation.

Japanese university lab test (Nagoya Institute of Technology, 2023) 2,100 cycles (accelerated 3× daily)DSC showed only 4 % drop in latent heat after 2,100 cycles

Years Until Significant Degradation
10 – 15 years (I lost part of this post somehow... but this was referencing using this system only for the winters Dec - Mar 120 cycles per year)

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Addition: It looks like straight Palm Kernel Oil (Note: not palm oil) , sealed in vacuum sealer pouches (7-layer PA/EVOH/PE structure Thickness ≥ 100 µm) will be a cheapert! It's melting point is not as exact as the paraffin/coconut oil, but it doesn't need to be exactly 25degrees. (something like 23-27degrees)


Ultra-simple version that already gives ~5,000cycles (most Japanese users do this)​


  1. Buy normal food-grade refined palm kernel oil (Amazon.co.jp 5 kg pails).
  2. Mix in 10% expanded graphite + 0.2% mixed tocopherols (Â¥500 worth). $3usd
  3. Vacuum-seal into normal LDPE pouches twice (double bag) with a vacuum sealer.
  4. Never heat above 40 °C.

→ Real fleets in Hokkaido and Okinawa are past 4–6 years onthis exact method with zero failures.
 
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Korishan said:
Virtually instantaneous.
Under heavy loads it is possible to have cells closer to the bus bars deliver more Amps than those further away. But their voltages will be the same.

This is why it's good practice to have Neg and Pos either on opposite ends of the pack or opposite corners to force current to flow through all cells equally
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Nice info. Thanks @Korishan
 
Don't overcomplicate it. Just a space heater and a temp controller and you'll be fine. My shed also houses the inverter and mppt controllers so it keeps the temp at above 10C. It's only when the temp outside drops below -10C then my space heater kicks in for short periods of time. My shed is insulated.

Here's the space heater I use, it only draws 200w. Any temp controller works.

I thought about sand batteries and stuff but never followed through. Mostly because I don't have excess solar power during the winters. And building the enclosures to make it safer would be more expensive than buying a space heater.
 
not2bme said:
Don't overcomplicate it. Just a space heater and a temp controller and you'll be fine. My shed also houses the inverter and mppt controllers so it keeps the temp at above 10C. It's only when the temp outside drops below -10C then my space heater kicks in for short periods of time. My shed is insulated.

Here's the space heater I use, it only draws 200w. Any temp controller works.

I thought about sand batteries and stuff but never followed through. Mostly because I don't have excess solar power during the winters. And building the enclosures to make it safer would be more expensive than buying a space heater.
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Yep, you could go this route for simplicity; but I'm interested in optimizing my system, especially for battery longevity.

Even Nissan has invested into active temperature management with the newest leaf's liquid battery management system. It's designed to maintain the battery pack within an optimal range.

If you can maintain your battery at least 15degrees or higher in the winter, you're going to get more efficient charging and improved longevity of the battery.

Check out how the internal resistance of different battery chemistries is affected by temperature here. https://www.researchgate.net/profil...rature-for-lithium-based-batteries-LiFePO.ppm.
 
I don't think not2bme was arguing against active temperature management, he is just using a space heater and a temp controller for simplicity. 🙂
 
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