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PowerWall - cabinet. Solar in steel cabinet?

SunnyPerth

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Jan 5, 2021
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Hi Team,

finally getting my act together and started my offgrid powerwall build; although not completely used off grid, it won’t feed back into the grid, and will run my appliances that need power 24/7 and an aircon for few hours in the evening.
I’m playing with the idea to fit everything into a steel workshop cabinet. See picture.

System will include 16x280ah batteries, MPP 5kw inverter. likely will put the PV breakers and some of the other breakers on the outside. Between batteries and inverter will be a divider, and fans on the left letting air out on top right.

Have looked if people have done similar, can’t find.. what are people thoughts ?
Note - all items in picture are to scale.

cheers!
 

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Seems like a good idea and reasonable...

The first thing that came to my mind is, if this is in a dusty environment, could put foam filters or furnace style filter cartridge on the cabinet inlets and foam or rubber-style gaskets to seal the door to door jams so air can only come in through the inlet vents filtered... Even in 'cleaner' kinds of areas, dust usually builds up a lot after awhile, so since you'd already have the enclosed cabinet thing going on, then you might as well use it to your further advantage and clean the air you run through it so you don't have to blow all your devices boards off as often or ever...

Also could add in remote cabinet temperature monitoring as well if you wanted to get fancy?
 
Yes, although I don’t expect a lot of dust, the filter idea is in the plan ;)
Don’t think I need to seal the doors, cabinet will be under pressure because of the fan(s), but could add if needed.

anyone here that has experience with the MPP’s in a smaller space like a cabinet ?
 
Yes, although I don’t expect a lot of dust, the filter idea is in the plan ;)
Don’t think I need to seal the doors, cabinet will be under pressure because of the fan(s), but could add if needed.

anyone here that has experience with the MPP’s in a smaller space like a cabinet ?

If you look in the MPP manual they give a spec about how much space should be around the unit (top, sides, bottom), to allow their fans to move enough air, check on that...
 
Yup, seen that. Not sure if it’s visible on the picture added, the dotted line is the clearance space around inverter. Obviously, space in cabinet is smaller, but that’s then also (one of the) reasons to add fans in the cabinet it self...
 
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For the people following this (if any ;-) )

I can easily have the batteries on the same level, which gives me another 20ish cm more space for airflow around the inverter. (see red dotted line)
Also thinking about changing the batteries from 2 times 1by8 to 2 times 2by4. Not sure why, but think it will work well.
 
Are you planning to run the cabinet fans only at full speed? Or will you set up a closed-loop temp sensing based control for variable PWM fan control (off your Pi)? If you are off-grid, then this could be a significant power savings feature, or if you are on on-grid then not such a big deal (although power savings is always a good thing)...
 
Definite going to build in some temperature sensors in the whole thing; and fan's (eventually) run variable speed. Obviously before I build it, no idea how much fan I need, and they might need to run all the time at full speed. But just equally it might be way less. Not sure yet if I will use the Pi for it or one or two ESP8266's + board. Haven't really looked into that part yet. But if I want to integrate it all, need something that sends the temp with MQTT and then has the option to (remotely) control correlation between temperature and fan speed. Should be easy enough.
 
I keep my off-grid backup system totally isolated. 25kWh of lithium ion cells housed in a 14ga Hoffman electrical box.

It may smoke me out of my home, but the steel box should contain any fire.
 

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I keep my off-grid backup system totally isolated. 25kWh of lithium ion cells housed in a 14ga Hoffman electrical box.

It may smoke me out of my home, but the steel box should contain any fire.
Wow - talking about a clean setup!!! That's just a mind blowing nice installation. Good idea, batteries inside, inverter on outside. For now I've installed the inverter, breakers, fuses, switches etc on a multiplex board, with the batteries below on a rack. This rack to eventually to be replaced with a box or cabinet. (still working on it). This is definitely an option. Thanks Murphy !!
 
Wow - talking about a clean setup!!! That's just a mind blowing nice installation. Good idea, batteries inside, inverter on outside. For now I've installed the inverter, breakers, fuses, switches etc on a multiplex board, with the batteries below on a rack. This rack to eventually to be replaced with a box or cabinet. (still working on it). This is definitely an option. Thanks Murphy !!

Call up your local industrial electric supplier and tell them you're a DIY guy who needs a large steel box. Ask them what they do with their rejected "ding and dent" products.

I bought my big $1100 Hoffman box for just $40. A neighbor down the road picks up scrap from a major electrical supplier and they give him all kinds of things that get rejected for one stupid reason or another. My "battery box" was destined for the trash dumpster because it has an 18 inch deep scratch in the paint. Not even a consideration for me, but they can't sell it because its damaged goods. So they gave it to my neighbor, he sold it to me.

I get large gauge welding cable the same way. All my 2/0 battery cable was collected from the 10 and 15 foot end pieces from the large spools. They buy a 1000 foot roll of the stuff and throw out the end pieces because they're not long enough to sell. I buy all kinds of things from the guy for about 5 cents on the dollar, and he just gives me lots for free as well. Wire terminals, heat shrink tubing, connectors, conduit fittings, junction boxes, unistrut hardware, etc. I even have bags of MC4 connectors because they ordered the wrong ones! LOL.

His main hobby is stripping the large copper wires they give him, saving up several thousand pounds, and taking it to the scrap yard.

These companies make so much money they don't bother with the scraps.. so bottom feeders like me get the stuff for super cheap.

See the junction box below the inverter? It had a missing cover screw so it was free. Crazy eh?

My neighbor's name is Matt, so we call him "Matt Depot" He has a 40 x 60 barn stacked wall to wall and floor to ceiling with everything electrical. When he needs my farm tractor to move heavy stuff, I help him out.. and he helps me.
 
I keep my off-grid backup system totally isolated. 25kWh of lithium ion cells housed in a 14ga Hoffman electrical box.

It may smoke me out of my home, but the steel box should contain any fire.
I really dig this setup, I'm doing something similar with a 48v 200ah lifepo4 packs.
 

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I really dig this setup, I'm doing something similar with a 48v 200ah lifepo4 packs.
That's nice.. but do you really need it with phosphate cells? They don't catch fire, just smoke a lot.
 
I just want it to be movable and seems like a nice way to achieve it.

That was a secondary thing here too.. I'm constantly moving things around. My cabinet weighs about 750 lbs.. takes a bit of oomph to get it rolling.
 
My Sunny Island test setup isn't as clean as Murphy's.
Built from a few spare 2x4 and some casters. At about 600 lbs. I can barely roll it.
If I rebuild it as a permanent setup, either split-phase or 3-phase, I'll weld together u-channel.

100 Ah 48V AGM, Sunny Island Charger, Sunny Island 5048US, 120/240V transformer, DC and AC breaker panels.
Everything is at least 3R except Sunny Island, and I made that watertight with a silicone sheet.

It has a 120V 15A plug so I can connect it to an outlet.
10/3 wire to patch output another panel.
MC cables to a couple PV panels on the roof.
I need to confirm what polarity the 15A 6-gang Outback breakers have. It was meant to segment a 600V string to 100V sections, but now I'm using it for parallel strings.

The transformer at 9000 VA is overkill for this setup but let me connect a 240V Sunny Boy.
I plan to use it as a balancing transformer on my grid backup system.

front back.jpg
 
Yes, although I don’t expect a lot of dust, the filter idea is in the plan ;)
Don’t think I need to seal the doors, cabinet will be under pressure because of the fan(s), but could add if needed.

anyone here that has experience with the MPP’s in a smaller space like a cabinet ?
If you put the filter on the fan and the inside is at positive pressure (as you stated), I can't see a reason for a seal. I have seen designers put a filter on a chassis inlet and a fan on the other end to suck air through. I always thought this was a bad design because it sucked in unfiltered air from every crack.
 
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