MPPT and bus bars in steel cabinet?

[timselectric]

The sad part is I've realized my solar batteries will probably out live me.

It's ok.
A lot of us are in that age group. lol

 

[pda1]

But....the good part is I file for Social inSecurity next month.....

 

[OffGridForGood]

I just stopped having birthday's - so I don't get a year older each year.

 

[OffGridForGood]

The sad part is I've realized my solar batteries will probably out live me.

Don't feel bad, I plant trees that I likely will not see to maturity, but I do it anyway!

 

[timselectric]

I just stopped having birthday's - so I don't get a year older each year.

I just celebrated the same birthday, for a second time.
You know that you are getting old, when you forget how old you are.
But on a good note, I was wrong last year. So, I'm younger than I thought. lol

 

[webbbn]

There are always more levels of protection, that can be applied. But you have to weigh the likelihood against the cost and effort.
Enough Voltage can create a arc across a gap. And enough amperage can sustain the arc.
Too much amperage on a conductor will create excessive heat.
Both of these conditions can cause a fire.
My point is that a battery built in a wooden box or frame, isn't a problem. As long as it's done properly.
Can you build your system in an underground concrete bunker, and feel safe? Yes
Can I build my system in my bedroom and feel safe? Absolutely.
You don't have to be afraid of electricity, but you do have to respect it.

Fair enough, but I wasn't referring to wooden boxes, where there is significant distance from the connectors to wood, but busbars and whatnot screwed to wood, where (at least in some pictures) it seems that the contacts are very close to the wood. It's convenient to just screw a sheet of plywood to the wall and screw everything to it, but it doesn't cost much to put some form on non-flammable layer on top of it. At least it makes me feel safer.

 

[webbbn]

I just celebrated the same birthday, for a second time.
You know that you are getting old, when you forget how old you are.
But on a good note, I was wrong last year. So, I'm younger than I thought. lol

I lost track of the number of times that I have celebrated my 29th birthday a long time ago, but now I'm like a kid again, just counting in reverse to retirement.

 

[timselectric]

I lost track of the number of times that I have celebrated my 29th birthday a long time ago, but now I'm like a kid again, just counting in reverse to retirement.

That was the downside of my birthday mistake.
I'm one more extra year from retirement. lol

 

[JJJJ]

one more extra year from retirement

What’s that? Hope I never grow up

 

[JJJJ]

Common house wiring is attached to or fished through wooden structures. No fire risk.

Difference is that DC is constant aka direct current. Things that will cause trouble is taking shortcuts with wire size; fuses and allowing poor connections which can allow arcing.

Metal raceways allow for a clean look but will not protect from poorly constructed systems. Open wires actually permit spacing and airflow. Not better but certainly not a safety hazard.

 

[OffGridForGood]

Common house wiring is attached to or fished through wooden structures. No fire risk.

and it is safe because the wire sizes are large enough and the breaker sized to protect those wires from overheating if they do see excess currents (which they shouldn't see if sized properly for their use). so we should learn and do the same for our solar set ups. Size wires properly for the loads, use fuses and breakers to protect those wires from excess heat under load.

 

[webbbn]

and it is safe because the wire sizes are large enough and the breaker sized to protect those wires from overheating if they do see excess currents (which they shouldn't see if sized properly for their use). so we should learn and do the same for our solar set ups. Size wires properly for the loads, use fuses and breakers to protect those wires from excess heat under load.

Not to belabor the point, but it's relatively easy to size wires correctly, and the fuses and breakers will protect those, but fuses and breakers will likely not protect against a failing connection. At 200A, it only takes 0.025 ohms of resistance in a loose connector to produce 1kw of heat. It's even worse if it arcs.

 

[timselectric]

A failed connection falls under improper installation.
There are a lot of what if's that can happen. You just have to pick which ones you are more concerned about.
What if there were an earthquake.
If the battery fell over. I would much rather have the terminals contact wood, than metal.
I purposely avoided any conductive materials around my batteries. My biggest concern would be a short across one cell. But I'm not going to place a fuse on each individual cell.

 

[webbbn]

A failed connection falls under improper installation.
There are a lot of what if's that can happen. You just have to pick which ones you are more concerned about.
What if there were an earthquake.
If the battery fell over. I would much rather have the terminals contact wood, than metal.
I purposely avoided any conductive materials around my batteries. My biggest concern would be a short across one cell. But I'm not going to place a fuse on each individual cell.

A connection can fail for many reasons (faulty manufacturing, stress fractures, etc), but, yes, it is likely due to improper installation. That's not a reason to argue against it. There are many non-combustible materials other than metal. I wouldn't recommend metal either, for obvious reasons. A thin sheet of drywall, even though it's paper covered, would be better than wood.

I'm sorry, but I really don't understand why an electrician, of all people would be arguing against basic safety procedures that cost essentially nothing. I'm sure you're perfect and have never made a connection that's failed, but not everyone is so gifted, so avoiding easy and obvious safety concerns might help some.

Maybe I'm more sensitive to this because I live in a desert tinderbox. I suppose there are other places where wood don't catch fire if you blink at it.

FWIW, I almost had a house burn down due to a makeup mirror...

 

[JJJJ]

I also prefer installing in a non conductive setting. I do have doors that can be closed and locked if needed to protect from young curious minds if needed.

 

[timselectric]

That is very well a possibility.
It takes a bit of effort to burn wood, around here.
You have to either be trying or really screwing up.

 

[SilverbackMP]

I also prefer installing in a non conductive setting. I do have doors that can be closed and locked if needed to protect from young curious minds if needed.

My DIY battery boxes (3/4 inch birch ply) are lined with 1/4 inch rubber floor material (also serves as a bit of cell compression relief). The floor of my shed also has the same rubber sheet flooring.

Could also use it on the top and bottom of metal shelves and perhaps coat other metal bits with flex seal.

Also, also metal shelving, boxes, server racks (I have a small server area in there too) are properly grounded.

 

[JJJJ]

takes a bit of effort to burn wood, around here

I spent five years in southern Indiana along the Ohio River. Humidity there was very high. Don’t recall any forest fire alerts during those days.

 

[timselectric]

I spent five years in southern Indiana along the Ohio River. Humidity there was very high. Don’t recall any forest fire alerts during those days.

I'm across the river from there.

 

[OffGridForGood]

My DIY battery boxes (3/4 inch birch ply) are lined with 1/4 inch rubber floor material

I can see the rubber for electrical isolation - but if it were to catch fire, rubber burns/makes smoke - I think this is why they use the fiberglass sheets between the cells typically: electrical isolation without being a smoke/combustion supporting material.
Fire Marshal told me once: "Smoke kills far more people than fire"

Humidity there was very high

Dry wood is a fantastic electrical isolation material, wet wood not so much.
on the flip side, dry wood can burn easily, but wet wood not so much.

I built my DIY cells into packs in birch ply boxes too, and like @timselectric I was mostly concerned about the isolation of the cell cases so used fiberglass sheets in some, and the stuff they call 'fish paper' (you see this in electronics; kinda green stiff paper stuff) in the others, since it was thinner and cheaper than the fiberglass sheets. I like the physical protection of the birch boxes, using a non-conducting material instead of metal, lets' me sleep better.

 

[SilverbackMP]

I can see the rubber for electrical isolation - but if it were to catch fire, rubber burns/makes smoke - I think this is why they use the fiberglass sheets between the cells typically: electrical isolation without being a smoke/combustion supporting material.
Fire Marshal told me once: "Smoke kills far more people than fire"

Dry wood is a fantastic electrical isolation material, wet wood not so much.
on the flip side, dry wood can burn easily, but wet wood not so much.

I built my DIY cells into packs in birch ply boxes too, and like @timselectric I was mostly concerned about the isolation of the cell cases so used fiberglass sheets in some, and the stuff they call 'fish paper' (you see this in electronics; kinda green stiff paper stuff) in the others, since it was thinner and cheaper than the fiberglass sheets. I like the physical protection of the birch boxes, using a non-conducting material instead of metal, lets' me sleep better.

That’s why it’s in a shed. It’s not a EV. Besides, the spray foam in the walls, floors and ceiling would likely release worse stuff. At some point, more and more risk mitigation starts running into the of law diminishing returns.

 

[JJJJ]

lets' me sleep better.

Ah yes. The true reason we are here and bounce our ideas off of others.

 

[OffGridForGood]

That’s why it’s in a shed. It’s not a EV. Besides, the spray foam in the walls, floors and ceiling would likely release worse stuff. At some point, more and more risk mitigation starts running into the of law diminishing returns.

I agree,
I put my entire solar set up next door in a steel building, concrete floor.
I make sure all the connections are tight, check them on occation, properly sized wire, MC for the PV DC as required around here, fuses and breakers in sensible locations. In the early days of my set up I ran around with a lazer temperature probe and checked what temps the wires and components got on a bright sunny day, or while my Official Solar Tester (wife) was pushing the system to the limits. That gave me a lot of confidence in the system seeing the wires stay at low temps even under high load.
One of the best parts of the DIY solar forum is reading the Up-in-Smoke postings and the safetey check to see what others may have discovered and we can learn from the easy way, before it is a problem.
I have learned a lot about the electrical code from members here on the forum.

 

[SilverbackMP]

My other issue was that I was under a time crunch. But I don’t think I would build the boxes much differently. The cells are individually wrapped in 2-3 layers kapton tape. Most of them anyway. I ran out for the last box and some are separated by flexible cutting board material.

 

[Zwy]

I'm inclined to put all of the solar controls into a steel cabinet and run the #2 wires to my multiplus 24 2000 which will be mounted next to the steel cabinet (with a door on it)
Put some fans in there to cool the equipment.

Why? I want to contain a fire in the event something bad happens.

Any opinions?

I would not do what you plan on a house system. On my truck camper, I mounted a toolbox to the rear and installed the Growatt AIO inside. It does get quite warm in there even with the inverter off and just the MPPT charging the battery. Yes, it does have a fan and outlet that is thermostatically controlled.




What are you afraid of? I prefer wires in conduit. I do have my Batrium K9's for my house system outside the battery box as these generate heat when balancing. Common sense should prevail.

Build a system like this where wires are protected, the battery is contained in a heavy steel box. You can look at the links in my signature if you want to see how I put things together.