Building a completely solar powered 120v outlet is...

initrdinitrd wrote 05/07/2022 at 20:35 • 6 min read • Like

....harder than it sounds.

Seeking to explore a new solar DIY project "hobby" to potentially power my entire home one day, a couple months ago, I set out to build a solar powered inverter using an adult sized panel,  a Canadian Solar CS6P-250PX, which I bought used on EBay in bulk last year. Not counting a 30 watt fold-out panel, with a built in charge controller (connected with a 15V DC/2Amp USB-C charging cable to a 178Wh Lithium Battery), this would count as my first modular system using off the shelf-parts.

The hardest part of the project has been not obtaining parts, but figuring out which gauge, amps, and wires are compatible. Compared to building computers for 20 yrs, solar technology is a naked science- nothing needs to be prepackaged, and even if it is, there is still a lot of different standards that needs to be matched. With a computer power supply, only the modular cables need to be used with the same power supply brand. But even then, the cables connections/pins are all housed in convenient plastic away from the variables of lug sizes and battery terminals. 

I've purchased the last 3 components today (tray cable, fuse holder, and fuse cable) and thus I have not yet begun assembling the setup, but I began this only after having found an already simplified tutorial, that explains it much better than some other ones. Finding a tutorial is only one part of the "puzzle." Another challenge is determining if enough alternative parts can be sourced at an affordable rate to make the project worthwhile. As a "mini" solar powered system using an 18Ah battery, and as a very first test project, I do not plan to spend more than $200 (If you exclude the $1644 I spent on the 29 other panels), and as of today, have remained about $25 under that budget. While I could use the same parts in that tutorial, there are some things/parts that are not explained since I bought the pre-made tray cables, and they made their own (and making my own cables is something I spent hours looking into a month or so ago, and was still left lost on the process) Also, there isn't a lot of information on how to connect ANL fuse cables to batteries, and which gauge and lug sizes are needed. For example the ANL Fuse Block says it uses 3/8" or 5/16" lug sizes, based on two Amazon reviewers. Buying the last component was hedging between whether a battery cable would fit 5/16" on one end and 3/8" on the other. Spending $9 on a pair at least let me feel I was getting a deal, and could repurpose them if they do not fit. 

I decided to not use lead-acid SLA/AGM, and not just for environmental reasons, but for compactness, and safety (If I am going to mess up the wiring and cause an overcurrent, with Lifefpo4, at least it won't cause a caustic mess-at least I imagine it won't). I do use lead acid in a UPS for work (a CyberPower CP850PFCLD) and in a car battery, but those are prebuilt, and I do not modify them for practical reasons. The other issue with pairing a battery with a controller is not all controllers work with lifepo4, or at least require manual settings around 14V.

Second, I wanted something that can power more than a lightbulb, and less than mini oven. The oven would be nice, but I don't feel like investing in tens of thousands of dollars for an off-grid-powered home with full heating capability. A practical use would be to have a UPS that can be recharged by a panel to power a modem and router, while using a laptop so there is an efficient and long battery during a possible power outage. My UPS lasts around 50-60 minutes, depending on how many monitors I am running. With a 65 watt CPU (an i3) it doesn't use a ton of power. But running a ultra low power laptop with a 6 cell battery, and using the UPC for just the modem, one could have almost 6 hrs of battery power, plus an additional 6-8hrs with a backup battery. Most power outages do not last that long, but it could save the need for taking an unpaid day off if working remotely.  

On to the part list. There are a million different ways one can build a solar powered system. The parts that I selected were picked due to affordability (with the exception of LiFEPO4), and of course, compatibility. Some cost more now or are discontinued, but there are similar products that can be used. Based on the results of this test setup, my dreams of having a solar-powered home may seem less idealistic than I thought, and left to the professionals.  

1. $56.00 ($1704/30 panels) Canadian Solar CS6P-250PX

2. $3.09 (Like New) Renogy One Pair of 9In 12AWG Adaptor Kit Solar
Cable Wire PV with Female & Male Connectors Connect Solar Panel and
Charge Controller

3. $7.82 (Acceptable) Renogy 10A Male and Female Connector Waterproof
in-Line Fuse Holder, 10A, Black

4. $15.54 Renogy 10 Amp 12V/24V PWM Negative Ground Solar Charge
Controller Compact Design w/LCD Display for AGM, Gel, Flooded and
Lithium Battery, Wanderer 10A

5. $10.97 Like New RENOGY 8ft. 10 AWG Wire Copper Tray Cable - Connect Charge Controller and Battery ($14.35)

6. $2.02 Renogy 20A Set w Holder ANL Fuse (currently $13.59 new)

"Condition: Used - Acceptable - Cosmetic imperfection(s) bigger than 1" on top, front or sides of item. Missing assembly hardware (screws/fasteners). Item will come in original packaging."

maybe mising the fuse?^ ;) lol: 

7. $8.97 Ampper 8 AWG Battery Cable Set, 20 Inch Copper Power Inverter Cables with Terminals for Car, Vehicle, RV, Solar Application and More (3/8" + 5/16" Ring, 1 Set)

8. $58.13 Lachy 12V 18Ah LiFePO4 Deep Cycle Battery 2000 Cycles
Maintenance-Free Rechargeable Battery

9. $7.99 Female Cigarette Lighter Socket, Y Type Terminal Plug Adapter
with Heavy Duty Extension Cable 10A Fuse 12/24V 16AWG Cord 1.6FT(2

10. $7.99 Ironton Power Inverter, 100 Continuous Watts (Purchased May
5, 2020- over 2 yrs ago!)

So there you have it, my labyrinth experience in procuring parts by being directed to a million different options and reviews that have polar opposite experiences and having to choose which parts seem to be compatible and which products appear to be unreliable. This hobby may not be for me. But I am willing to wait on exploring it more til I put it all together after the remaining parts arrive next week. 

Also, I know I picked a yuuge solar panel for this, but it is the only size I have that is not integrated with a USB charger.  It would be nice to have a 24V battery, and see if the Renogy charge controller could charge at the rated 250watts, but I am not sure if it would work either, and it would probably cost more. How fast can this 12V battery charge? Hopefully fast enough under 4-5 hrs. Ideally on a single panel and so that it could be recharged fully every day. Scaling that up to power a washing machine is beyond my pay grade ;)

I also have 4 more Renogy 10A charge controllers which I got on Amazon for an amazingly low price of $7, but that was more of an impulsive buy than anything that I would practically scale it up to. But I would use them if this test produces something that I could see replicating in additional projects- "decentralized power stations" is what I have in mind. Apparently the 10A charge controller can accept up to 260 watts at 24v:

 and 130 watts at 12V. So I do not know if the panel will charge at that rate, or if it will cause an overload (the fuses should help with that). I also don't know if the 10A MC4 inline fuse will be sufficient, as the Optimum Operating Current is 8.87A (at peak solar irradiance perhaps?).

I think this is the best way to conclude this article, leaving the doubt and suspense to maximum effect. If you have spotted any clear electrical incompatible issues, feel free to comment below. You'll save me a fuse replacement, at the very least, and that would be very much appreciated :D 

Thanks for reading!

Update: Upon reading a PWM comparison article, it seems I will need a 30A charge controller, which can handle up to 400Watts.