House conversion to 12VDC: system build sanity check and questions

[geekboy]

For a number of reasons, I've decided to convert much of my house's electric usage to 12VDC powered by solar (and, soon, wind). I validated that it was doable with a 100W panel, 65AH AGM battery, and a cheapo 40A charge controller from Amazon. Now I'm ready to scale up to full-house 12VDC where it makes sense to convert things. But I want to make sure that I've got my bearings, and I have a few nagging questions still.

For what it's worth, my average "peak hour" power usage on 120VAC is 200-300W, with an absolute peak (everything sensible turned on at once) of about 500W. Of course, I occasionally run my microwave and stuff akin to that, but those are more "burst" loads and I'm not accounting for them in any calculations I'm doing right now. Also, wintertime brings space heaters, and I'm not sure how well they fit into the 12VDC lifestyle or if those should stay 120VAC. (But I touch on heating below!)

I also do not intend this to be a grid-tie system. I intend this to be its own self-contained little thing.

This is a long post, mostly so you can all (hopefully) see where my thinking is, in hopes of helping me avoid expensive (or life-threatening!) mistakes.

I split this into two posts, to help make it easier (I hope) to quote reply on what I have chosen and what is all questions for me. I hope that's acceptable around here.

What I've picked up so far:

• 200 AH deep-cycle AGM battery - I'll end up with 4-8 of these, depending on how much capacity I end up actually wanting. 4 feels "right" right now from what I've been able to calculate, though... Or am I totally under-speccing and should have like 16 of these batteries?
• Xantrex C60 - As a load controller (LVD), since 60A is more than sufficient for my needs as far as I've been able to calculate so far.
• Battery disconnect switch - Safety first! Should I add one in line with each controller? Or just the load? I learned long ago on 120VAC to never trust a breaker/fuse alone.
• 12VDC light bulbs - I've started converting fixtures, running new LV wiring to them, and adding new LV switches and dimmers (I never knew I wanted dimmer switches for my porch lights before!). Some fixtures wanting replacement got replaced at the same time. (Also, this house is old enough to have knob & tube, so it's also a great opportunity to pull out 100 year old wire, which I'd have to do soon for 120VAC anyhow.)
• Various 12VDC fixtures, to ensure adequate lighting on 12VDC alone. One example.
• Even my main PC is now 12VDC (and, of course, car chargers for the laptops).
• I've surely missed a few things.

What I intend to order soon:

• 60A breaker for my C60 load controller. Is something like this appropriate? Does it go on the positive or negative leg, or does it matter?
• Roof-mounted 445W PV panels - 4 of these seem like a good start. But should I go for 8, considering no more than 60A absolute max drain on the battery bank? 16 (though that honestly feels like overkill for PV + wind with 60A max drain)? Are these a good deal? The price seems good and they claim to have a warranty that's almost too good to be true, so I'm honestly a bit suspicious.
• Charge controller(s) for the above panels - Can I run them all through one controller with a PV combiner box? Should each panel or pair of panels have its own charge controller? Do I want PWM or MPPT for real? From what I have read, PWM is better on less bright days to be able to get charging at all, while MPPT is better at sucking the power from the panels once they get above the threshold initially. Is that correct? For what it matters, I'm in Michigan's Lower Peninsula, so short winter days and occasional snow are a thing.
• For off-grid entertainment, a 40" TV (the largest 12VDC I've found, so if anyone has better options, I'm interested) and a Blu-Ray/media player (this also looks like the only viable choice, and I'm waiting to hear from them as to its availability in hopes that it won't cost me $250 on Amazon/eBay/etc.). I can operate my Amazon Fire Stick off USB or my Roku off 12VDC, as well.
• Some exterior lighting solutions besides just retrofitting my front porch. Things like this look interesting to me for replacing my various not-great solar motion lights.
• An inverter. It feels like a good idea to have one of these available, for "just in case", if nothing else. (Though my 120VAC panel has a manual transfer switch, for eventually adding a generator to that system, so ideally it *will* be "just in case" for the long run.) Probably 2000-4000W since I should have enough juice on store for that much maximum power if it's needed.
• A wind turbine and associated charge controller. I have a company in mind to order from, but they're out of stock of the one I want for a couple weeks. I won't go into detail on that aspect of the system as this is the Solar forum. (My diverter questions are still relevant for the wind, too, though, I suppose.)

 

[geekboy]

What I need help picking out:

• PV lightning/surge suppression. I honestly don't even know where to start on this.
• Diverter loads.
  • I'm thinking that I want to figure out how to convert my natural gas hot water heater to solar, but I haven't figured out what I need. (Everything looks to be for electric hot water heaters.) Bonus points for it being gas + solar as a result!
  • I also would like to have hot air heaters as a diverter load (and swap those out seasonally with resistors or something else, probably). But I haven't figured out what's even available for these. I'd prefer in-wall if that's an option. I've literally found two styles for sale, both from the same seller. And it's extremely unclear how they mount and such.
    • My primary heating is powered by natural gas. The diversion loads would help reduce my gas consumption (if it's "waste" from the RE, I may as well reclaim it, right?), as well as my 120VAC space heater usage in spaces which get cold spots with the gas heat if it's not high enough for the room.
  • What other loads make sense besides just a resistor? I'd like to put my "waste" electricity to good use year round, if at all possible. I'm pretty sure that things like heat pumps don't exist, though they'd be the most awesome option in my book.
  • Can one reasonably build one's own diverter load, for example a heat pump for year-round seasonally-appropriate temperature control?

As for the questions that didn't fit above:

• How do most people handle grounding? A separate ground wire? Bonded to neutral and then ground the load controller?
• Do I need to worry about adding any diodes or other isolation, with the multiple controllers? (Again, 1 or more PV controllers, a load controller, and a wind controller.)
• What diodes should I be putting in place for the charge controller(s), since I want diversion loads?
• Are there any good choices for battery meters for my battery bank? I'd like to see per-battery stats, at the least. The ones I see recommended most often are all for lithium batteries, and I'm not able/willing to take that path just yet. It's definitely something I'm leaving open for when these batteries start dying in a few years, though.
• Is there any real benefit to getting the C60 panel display? After all, I'm using it as a load controller, so the only useful thing it might tell me is how many watts/amps I'm drawing at that moment, right? A good battery meter should also tell me the same? As far as I can tell, calculating runtime is always up to me, unless there's a device out there I've not seen.
• I've seen mention around the net of some kind of "standard" 12VDC plug to e.g. wall mount, but I can't figure out what people are talking about. I'd prefer something safer and better than a barrel jack, with bonus points if it's available as a keystone jack. (But it's also OK if it requires a full on faceplate of its own.)
• As I'll be running wire throughout my house as I convert things and adding jacks where relevant (such as my office, as I've even converted my main PC to run happily off 25A max 12VDC, including a Thunderbolt display, making it my largest power draw by far but also my biggest wow factor!), what are some good reputable vendors of spools of common size wire (14 through 1/0 AWG, depending on length of run and wattage)? Preferably at cheaper prices than Amazon has them for.
• Is it a bad idea to mix/match battery brands as long as they're the same type and same capacity?
• Does my battery bank need balancing? I've seen both yes and no answers. Is this a "contact Renogy and hope for an answer" sort of thing?
• Is there a good way to try to prevent snow buildup on my panels?
• Is there an obvious and "correct" way to wire all these controllers to the batteries? I saw the FAQ post, but it didn't seem to cover the case of 2 or more charge controllers plus a separate load controller.

Do I have my head screwed on straight? Am I missing anything obvious? Is this where everyone points and laughs because I made noobish mistake after noobish mistake while trying to figure all this out?

Also, I had considered 24/36/48VDC as well, but since all my usage is going to be at 12V, it just didn't make sense to convert down to 12VDC 60A for *everything*. Though I suppose it's an option if it makes life better somehow?

Most of the resources out there just don't fit all the pieces together quite right, so I'm second guessing things a lot since I don't have infinite money to keep trying again if I blow things up. But aside from protection, grounding, and diverters, I think I've got everything pretty much in place to chug along at the project.

Also, please feel free to point me at relevant posts I may have missed in my searching.

 

[geekboy]

In the past week, I've spent much time trying to figure out the whole charge controller question. I simply cannot figure out whether it's considered better to have a separate charge controller per panel or pair, or if it's better to have one charge controller with all 4-8 going through a combiner box.

Any thoughts?

 

[Rednecktek]

While I admire the ambition, I have to wonder why you don't just stick with 120v and use an inverter? My thoughts being this:

1: You can go to any hardware store and get a 120v light bulb, or switch, or fixture. Not so much with 12v.
2: Using an inverter takes the battery voltage limitations out of the picture. 12v? 24v? 48v? The light bulbs and laptops and microwave don't care, they're getting their 120v they expect.
3: If you ever try to sell the house it'll never pass NEC and you'll have a hard time.
4: If you're pulling wire anyways, romex for a 20a outlet circuit is going to be cheaper than bulk 12v wire and easier to run since, as before, all your outlet boxes and receptacles and such are designed for it. 20a of DC takes thicker wire at 12v than it does at 120v. More copper = more money.
5: The wonderful thing about standards is that there are so many to choose from! Especially in the DC world where there isn't one central governing body like the NEC, so the plugs from Brand-A to plug into a Brand-B socket and replace the Brand-C light bulb may not (probably will not) all talk to each other.

Just because you wanted a sanity check.

Now, on the other hand, if you were starting with someplace like my camp where it started life as a travel trailer that was expanded on, it's already got a lot of 12v stuff wired in and you'd be stuck with a 12v system, but even then I could wire in an inverter to the AC inlet plug and just go to town.

 

[12VoltInstalls]

because you wanted a sanity check.
if you were starting as a travel trailer that was expanded on, it's already got a lot of 12v stuff wired in and you'd be stuck with a 12v system, but even then I could wire in an inverter to the AC inlet plug and just go to town.

I validated that it was doable with a 100W panel, 65AH AGM battery, and a cheapo 40A charge controller from Amazon. Now I'm ready to scale up to full-house 12VDC where it makes sense to convert things.

If you already have a 120V panel… two things: 1) keep the 120V stuff 120VAC and supply the panel from the inverter 2) solid copper is a terrible feeder for 12VDC
(there’s more but no sense since the former two make sense.

Wire your 12Vdc stuff separately- with wire gage / voltage loss in mind. There are a number of available 12V LED lights that aren’t ‘bulbs’ or ‘fixtures’ that are manufactured to supply the value-added manufacturing segment- components if you will. This is milliwatt components you would employ for convenience/presence lighting. 6paks for <$10 are not uncommon, so buy 3times what you need as they may be irreplaceable with a direct-swap part in ten or twenty years when their life expectancy is realized.
For “work light” or use/reading/eating lights the RV industry has a gazillion dim/bright LED switchable surface and recessed options that are 5- 60 or so watts. This lets you have sufficient bright light when you need it without drawing the batteries 100% of use time (because of the low-watt presence lighting).

Further, with 120V availability you can implement a <$500 fridge and have other 120V options like a coffeemaker

I use both 120V and 12V as above. But as in quoted post, I’m in a camper. Not as in quoted post I fresh-wired everything through a bluesea 12V fuse box. (New 2-wire sheathed 12V wiring = my 90mw lensatic LEDs were vastly brighter)

Deplatforming 120VAC devices (outlets) makes no sense. In fact, people have (and will) made sensible and wise arguments for not 12V whatsoever and from a purely utilitarian perspective they’re right.
I do, however, hold strongly to my opinion that the simplicity and redundancy of two sources of basic lighting and charging stuff in a small solar power environment is a worthwhile investment especially if a backup SCC and inverter aren’t on hand.
(I have two backup SCCs and just acquired a spare 1500W inverter for my 1200W, and have an alligator clip 300W- all true sine format)

You list some quality equipment, some not. At the higher-end pricing points don’t matter and backups matter less, but $200/$250 can buy a decent low priced inverter and feels like a good idea still.

Maybe these thoughts will help you; maybe not. They are free and hopefully they will help you have a dependable safe power system.

 

[A.Justice]

I've seen mention around the net of some kind of "standard" 12VDC plug to e.g. wall mount...

Anderson power poles (or Anderson SB series) are the general go-to for standardized 12 volt DC outlets. They even sell "wall" plates.

I get mine from PowerWerx (LINK).

XT (XT30, XT60, XT90) connectors are another option, but they require soldering, so it's up to you if you'd like to solder every single outlet. They work great though.

what are some good reputable vendors of spools of common size wire

Don't skimp on wires. Amazon sells copper-clad aluminum as pure copper pretty often. I order important wire from Muller Electric.

Mueller Electric - Buy Electrical Components & Products Online

Mueller Electric is a leading supplier of electrical components for a wide range of industries. Buy quality products or view our customization options online!

www.muellerelectric.com

You also mentioned a 12-volt TV somewhere in your post. Just an FYI, most TV's are already 12v. Check the output voltage on the black box or "wall wart", most (at least ones that aren't huge) TV's are actually 12v.

Voltage drop at 12 volts will be a very real problem for your setup. I would make sure your batteries are in the center most location of your house, and get lighting that can take a range of voltage. A lot of 12 volt automotive lighting will take between 8-15v, it will be a little dimmer, but it should turn on even with a large drop in voltage over a good distance.

 

[12VoltInstalls]

This is an example of what I often use for wire. Lots of sizes and lengths in the link. Pure tinned copper. https://www.amazon.com/dp/B000NUYBW0/ref=cm_sw_r_cp_api_glt_fabc_dl_WP0VPXW6GBWWXTGJ5D44?psc=1

I use stranded pure bare copper fairly often from reputable manufacturers but the marine stuff is great if cold/warm cycles create condensation- or if you’re doing a boat…

This what not to use: https://www.amazon.com/dp/B08FMMZHQ6/ref=cm_sw_r_cp_api_glt_fabc_TRCDXSWDJQ1Z3VZNNBHG
Ignore the gage; do you see why?

The thing with 12V is that over-wiring (bigger gage) compensates somewhat for loss over distance. For almost everything 12V if the load calls for 16ga I use 14; 12ga? I use 10ga. Performance is optimal that way (I always fuse for the load + 15-20%. 10ga at shorter lengths is rated for 30A; 12ga is 20A. My water pump is 6.5A and I run ~20’ but used 12ga wire and a 10A fuse. Capisce?)
With low-watt lights you can parallel them on a single circuit. “Local” usb charger devices aren’t a good idea unless switched because they’re tiny leaches but if the wire supports it you can parallel those through and run through a switch.

I have an affinity for these: https://www.amazon.com/dp/B07SB55HS...abc_MMG4YEKBS1RFWJG09GNR?_encoding=UTF8&psc=1 which are fine because seriously: what are you going to plug in to 12V outlets? Like almost nothing, and never over 15A. 120V is for things that need high power.

most TV's are already 12v. Check the output voltage on the black box or "wall wart", most (at least ones that aren't huge) TV's are actually 12v.

“most TV's are already 12v”

I have not run my tv in two? years now. However, I understand or have been told that IF you open the case on, for example, a 52” LED TV and the power supply is separate from the pcboard you can check it for voltage and often they are internally 12V as well. I intend to explore that… any insights would be welcome.
However, there’s no practical reason to do that as at this point my inverter is on 24x7 anyway. I think my 50” is like 65W? So no biggie either

 

[12VoltInstalls]

OP joined Sept 6, last seen Sept 12th.

What have you come up with for solutions?