Small DC only solar system - PEP BB electricity.sand.solar

I would like to present the following as an alternative submission (this setup includes an inverter and powers AC devices only at this time, and I built it 2 years ago so I don't have pictures of the unassembled parts):

I built this 24V system with the intention of using it off grid when I retire, and I purchased 4 used 6V batteries as I had several years to go and if I had to learn the hard way, better to use inexpensive batteries. The system consists of 4 300W PV panels, wired into 2 parallel strings of 2 panels in series (2x2). The panels can each produce a bit over 30V at a bit under 10A in standard conditions. Weather conditions and edge shading can cause higher voltage spikes. The typical input voltage sits around 70V and is managed by the charge controller. The charge controller can handle up to 140V before voltage protection kicks in, and can handle up to 60A input.

The panel input runs through a breaker, and then into the charge controller. The charge controller positive output runs into another breaker, then to a second breaker which connects to both the batteries (on the opposite side of the breaker) and the inverter (on the same side of the breaker). The negative feeds for the chrage controller, batteries, and inverter all attach to a negative bus bar, and the negative bar, charge controller, and inverter are wired to a ground bus which goes outside to a copper grounding bar in the soil. The panels are also attached to that grounding bar.

The batteries are wired in series with heavy gauge wire to minimize resistance. Each battery is rated at 220AH, so being in series this results in 220AH*24V=5.28kwh of total capacity. Since batteries can take permanent damage if their charge goes below 50%, the usable amount of power is limited to 2.64kwh in this setup. Typical daily use currently is around 800wh per day, powering my cable modem and wireless router if I leave them on over night. The inverter has a power switch, as does the power strip that these devices are plugged into so you can cut power to non-essential items when not in use, to minimize any phantom loads. When I first set everything up it was summertime and the panels would receive a good amount of sunlight (winter sun is blocked by trees in my tiny city lot) and I also powered my refrigerator using this system. That brought total power use closer to 2kwh per day and the used batteries were barely able to stay above 50% charge by early morning when they could recharge. I've avoided mounting the PV array to my patio roof at this time, but that would certainly improve performance as would adding 2 additional PV panels, one to each string for getting proper charging levels (10% of 220AH=22A input, while my system is closer to 19.3A max input) and higher overall power output.

While I don't normally charge my phone, I've included 2 pictures (one is a screen capture of the phone since I don't have another to take the picture) of the phone plugged into the inverter and showing it is receiving a charge. The highest power use I've attempted included the fridge, a power strip for my PC and other gear, and my window AC unit (rated at 960W) which was around 1500W when all were running at once. The inverter could handle that, although the cooling fans would turn on in that case. The highest PV input I saw was at that same time, the charge controller was reporting around 1100W+ out of a possible 1200 as conditions are rarely perfect. This was obviously not enough for everything, but I only ran the AC off solar once to see it work, and normally just the fridge, wi-fi, modem, PC, and light were powered that summer.

So here it is.

Here is a 12v system for the shed. The battery is a 50AH, 12V, deep cycle, lead acid. Without any solar input it will just cover 100W for 6 hours, 50*12=600Wh. I used my phone to take the pictures, so I'm charging my ereader.

edit - The charge controller has a pair of built in usb ports (5V, 2A shared). There is a panel mount usb extension cord underneath the light switch, I installed this to protect the connector on the charge controller. The ereader is charging from that port.

The system is link to another shed with a 12v socket and USB socket (you can see the installed cable on the side of the shed). The lights won't be wired up until we fix the leak in the roof.

I wrote this up already once and it closed on me, so my explanation is going to be a little less enthusiastic. This is my second post, and first BB attempt.

Goal is a DC solar setup that can sustain 100w@6 hours.

Math is: (100w*6hrs)/120v via inverter, to total 5ah. Battery size needed is >=10ah to account for 50% depletion max on AGM battery, for the life and health of the battery. EzPz.

So It's very windy, and desert-y at the time of install, so I didn't manage to get before pictures of attaching the batteries for my own use (5th wheel conversion to solar). The wind was desert'ing all over my face, so I just did that part without playing photographer. The solar setup can just as easily completely bypass all that 12v connectivity from the 5th wheel.

Anyhow... I used 2x 255w solar panels, along with a parallel mc4 y cable, leading into the Renogy 40a mppt solar charge controller. From there, the system runs into 2x 100ah 12v AGM batteries,  that replaced the ancient 35ah batteries of the original house system (also pictured, so you can see that I did in fact install these guys). Off of the battery bank, I fed a 400w inverter, which has a 5v USB charger on it. The inverter is throwaway, and I'm assuming a 70% efficiency from it. Not super fond of it, and I don't recommend it.

I cannot afford the 12v outlet, as it's not essential in my current (haha get it? Current... Electricity... Haha) setup, nor do I have a need for it at present. So instead, I would like to propose trading the 12v requirement for the fact that this is my real world, live-in application of solar, and wasn't built solely for a badge, or demonstration purposes. But I'll leave that up to you.

Edit: the 12v cigarette lighter is a box enclosure connected to the battery directly via one of the wires on the batter bank. And if you look closely, you'll see there are two alligator clips connecting the inverter to the battery bank. I've also added a picture of the inverter, showing the alligator clips that come in the package.

Anyhow... I'm hitting the submit button. If you can read this, that means it worked. Thanks for your consideration.

Panels are "mounted" and  rotated via cinder block currently, as they're not going to be permanently housed here. This is just their temporary home for a few more weeks while I stage and prepare to move officially to the site. I have some local L beams being held for me in my property's neighborhood, to create their pretty mounts in the future. All of the components for the kit were acquired independently of each other, so the panels came "as-is" with no mounts. This is our poor man's effort, this far. I've ran it since last night, got the 3 way fridge working, all my internal lights, furnace, etc. Which was "good enough" for me, for now.

No problem Lex. Looks like you added the 12v socket picture. Once you get the panels mounted in their final location just add that pic.

Here's a link about panel orientation.

Here was one of our first DC solar set ups.

There are four 85 watt solar panels hooked up to a midnite solar charge controller that is connected to 3 100AH batteries. The batteries are running a DC freezer that uses 900 watts per day. You can see that the green light is lit on the freezer in the lower left corner.

The panels produce 85x4= 340 watts per hour with 10 hours of sun. So 3,400 watts per day. The 3 batteries are in parallel so the AH are tripled to 300 AH. At 12 volts that gives you 3,600 watts of stored energy.

So the requirements said

Side Notes:
If you have an alternative solar installation that you'd like to do of a similar complexity, post below and ask if it could be added as an option.

So I would ask if this as an acceptable alternative complexity wise?

Thanks