Solar panel system

[andyvh1959]

I am installing a four panel solar array on the south hip of the roof of my new detached garage project. I've always been curious about solar so I am going with a simple off-grid system of 880 watts total, 12v DC. I already have a MPPT charge controller and a DC breaker panel to wire into the garage overhead lights. I also plan to use deep cycle batteries as the backup for the cloudy days and night work. I also plan to wire a bunch of outlets to the array system so I can have multiple 12v outlets to charge my motorcycle collection.

I plan to wire all the LED lights and outlets with 14-2 wire just for ease and common wiring products. Also, just in case the solar panel system doesn't work out, the circuits can easily be connected to the 120v AC I have routed to the garage from the 100 amp meter on the house.
I am open to any and all suggestions.

 

[dcg9381]

I've never done "residential DC" - I assume, pending correction on this forum, that it's just considered "low voltage"...

I like the wiring idea for "conversion" to AC if you decide that this isn't great or if you decide you don't want to deal with battery hassles.

My only comment is this: You need a low-voltage cut-off. Some controllers have this built in. I've done a small version of what you're doing (80 watt DC) to power a gate, IP cameras, and some lights.. But inevitably, there would be a spell of 7+ days with clouds and I'd over-discharge the deep cycle battery. Went through a few batteries before I learned my lesson.

 

[andyvh1959]

Exactly, that's why I spent the bucks on a well reviewed MPPT charge controller with the low voltage control built in. The charge controller does just that; avoids over charging on long bright sunny days, and avoids draining the reservoir on long cloudy days.

Since its all low voltage I could actually wire it all with automotive style stranded wire. But the cost for standard 14-2 wire is probably better, and I'll use all standard 120v switches, but the "outlets" I may use something like a European 2-prong style to make sure it looks different. I can always change it out someday to standard 120v outlets if I decide to change from the low voltage solar system, I'm just intrigued by the idea of all my shop lights being low voltage bright white LED powered by the solar system and not spinning the meter on the house no matter how long I leave the shop lights burning.

I've read that 16' foot long low voltage LED string lights can put out plenty of flood style light for a shop, especially one with white walls and ceiling. My garage has a vaulted ceiling on which I'll run four 16' long LED string lights, for only a total of 36 watts each or 144 watts total. https://www.ebay.com/itm/123771074945?ul_noapp=true

So I can run all the shop lights and keep charging my many cycle batteries. For workbench lights I found a 16" LED 12V light bar (off road use style) for $17 that I can mount on a flexible arm. I'll probably get about six of them to use around the workbench, welder, bike lift, etc. I've even heard of mounting 12v LED light strips to the bike lift, to shine light up underneath the bike.

 

[Zeke]

I wanted to convert some of my house lighting to 12v and I got shot down. There was considerable conversation about the NEC and this. I don't think that aspect has changed.

If it's permissible, I got bad advice here and elsewhere.

To be clear, I was going to use regular UL rated fixtures with 12v standard base lamps.

 

[Bretny]

Why bother with 12v lights if you already have 120v? Just run that circuit off an inverter.

 

[gte718p]

Why bother with 12v lights if you already have 120v? Just run that circuit off an inverter.

Cheap, environmentally friendly, long lasting, cool (temperature wise), and essentially free (after the sunk cost). Inverters stepping down 120v to 12 are pretty inefficient vice a straight 12v system. Plus another component to wear out and break.

I use a lot of solar power, but I have been in involved in solar car racing for almost 25 years now. 12 volt lighting gives you all kind of options that 120v doesn’t.

It sounds like you are planning on airing conventional boxes and outlets with 12v? That is a bad idea especially if there is 120v present. Obviously accidentally plugging a 12v dc fixture into a 120v socket goes bad quick, but pouting 12v dc into something expecting 120v ac can also do some interesting and undesirable things. There is not a standard 12v outlet, but I recommend bus bars and weather pack or moped connections.

 

[Bretny]

Now your just adding more complexity to a system that didn't need it. Put in a tiny inverter small enough to run the 120v lights you already have and wording that's already there. Inverter efficiency didn't really matter much when you consider the line loss on low voltage DC wording or the price of heavy gauge wireing.

 

[cybrdyke]

I've read that 16' foot long low voltage LED string lights can put out plenty of flood style light for a shop, especially one with white walls and ceiling. My garage has a vaulted ceiling on which I'll run four 16' long LED string lights, for only a total of 36 watts each or 144 watts total. https://www.ebay.com/itm/123771074945?ul_noapp=true

The lights you linked are 72 watts per 16' section so you'd be at 288 watts with 4 of them.
The tape lights are not for general illumination. They're toys. You'll be disappointed with the results. For the same money, you can get some cheap LED strips that will produce actual results. I have a 100w solar panel and use them in my 20x30 shop.
CD

 

[andyvh1959]

Opps, right about the total wattage. Thanks for the input about the LED strips, I'd certainly prefer to use products that others have proven already. My new shop ceiling is vaulted, going from 9'-4" to 12' at the peak. Can you send me details on the LED strips you used in your shop?

And to Bretny, I fully understand, and yes I am adding complexity. But like I said in my initial post, this is my first foray into solar, I've been curious about it for some time. Yes, it would be much easier to install an inverter and run everything off the power grid. Yes the LEDs run off the grid would reduce the wattage needed, but some power is lost to heat in the inverter. I want to learn about being off the grid, so this is my learning experience with an off-grid low voltage LED system. If this proves out I could be doing a lot more of it in the future.

gte718p; yes, good point about the hazard of plugging in a 12v DC device to a 120v AC outlet. But like I said, other than the 14-2 wiring, I plan to use a 12v power outlet (like an automotive style) making it unique to only 12v DC so there is no potential of a wrong connection. Plus I'd label or identify every 12v outlet to make it clear. Aside from that, its all just my shop and not for others to be working in it.

 

[ddawg16]

I'm a little late to the game....

But I think the OP has a viable plan. Using 14-2 gives him the flexibility to go back to 120 if he wants.

However, I do caution you on the lead acid batteries....specifically, out gassing....make sure they are properly vented. You don't want a build up of hydrogen gas.

If I may suggest an option....try to find a used EV car battery. Chances are, it's going to be a collection of 24 to 48 Vdc Li packs. Those, even used, will have considerably more capacity than lead acid and take up less space. DC to DC converters are pretty cheap.