# Custom solar panel setup

#### k1ng 1337

Joined Sep 11, 2020
85
Hi I am interested in purchasing a large solar panel to power my toys. I would like to have a 120v ac "node" (think of a 3 socket extension cord) as well as 0-20v regulated DC isolated from the AC.

I would like to build this myself as a low power solution so I can run my gadgets and toys without running up the electric bill among other interesting off grid experiments. I think it would be interesting to track trends and use the power available in an efficient manner and if there is extra juice then run things that would otherwise always be left off to "save power".

#### Audioguru again

Joined Oct 21, 2019
3,173
If you are using enough electrical power to run up the electricity bill then a huge solar panel (plus the inverter that you will build) will cost much more. Will you have a huge battery to use at night and on cloudy days?

#### KeithWalker

Joined Jul 10, 2017
1,779
That is going to be a very expensive project, as Audioguru stated. It will probably not even save enough expense to pay for it's own long term maintenance..

#### MisterBill2

Joined Jan 23, 2018
8,744
Certainly this will not be a money-saving project, but it can be both educational and a lot of fun. You will need solar panels able to provide enough voltage to charge a 12 volt battery because you will need a stable DC supply, and you may not want to throw LOTS of money at this project. The battery charge circuit will be fairly simple, there are a lot of published circuits around, just check the "schematics for free" website, which also has a lot of circuits for assorted power inverters.
You could also buy enough cells to charge a set of two 12 volt batteries and have plenty of zero to 20 volt power for experimenting with.

#### andrewmm

Joined Feb 25, 2011
1,466
Hi I am interested in purchasing a large solar panel to power my toys. I would like to have a 120v ac "node" (think of a 3 socket extension cord) as well as 0-20v regulated DC isolated from the AC.

I would like to build this myself as a low power solution so I can run my gadgets and toys without running up the electric bill among other interesting off grid experiments. I think it would be interesting to track trends and use the power available in an efficient manner and if there is extra juice then run things that would otherwise always be left off to "save power".

As others have highlighted, This has a few parts

Generation, The panels are not cheep, naturally they will only deliver power when the sun is out,

The unit that connects to the panels, can be simple, or smart, Simple is much lower efficiency, than smart that adjusts the load on the panels to keep them at maximum efficiency ( panels voltage / current is not linear )

What to do when there's not enough sun, or at night , you need batteries or some other means of storing electricity .

As you can see, there are a few variables, which you can optimise depending what you want.
I have friends who got hold of bunch of 2v cells , very cheap, they just need toping up with acid ever week or two,
for them, the cost / fun of making a solar store was easy,

Myself, I have 6 Kw on the roof of panels, but no battery . I do divert what I can into the hot water / electric heating as needed, I have an Arduino system that does that for us. In the UK, the government system is you export what you don't use, but get a payment for all you generate, thus is in my advantage to use as much of it myself .. The system has paid for itself after 6 years, and the panels have another 19 years guarantee on them,.

I have another person I know, who lives well off grid, to them, batteries and panels are an essential.

For you, the equation is where the choices lay,

#### Bernard

Joined Aug 7, 2008
5,788
How much power do you need? 100 Ws of panel about US $200. AC inverter about$ 150.
Battery not needed as you said " use the power available".

#### nsaspook

Joined Aug 27, 2009
8,382
How much power do you need? 100 Ws of panel about US $200. AC inverter about$ 150.
Battery not needed as you said " use the power available".
Most off-grid inverters on the market require batteries to operate but you can trick (not recommended) them to work without batteries.

#### Bernard

Joined Aug 7, 2008
5,788
A battery is a good investment, stable 12 V output, more peak power for motor starting & power for short sun blockages. Harbor Freight 400 W inverter, 2020 catalog = $40. #### nsaspook Joined Aug 27, 2009 8,382 A battery is a good investment, stable 12 V output, more peak power for motor starting & power for short sun blockages. Harbor Freight 400 W inverter, 2020 catalog =$ 40.
Don't waste money on that inverter.

#### k1ng 1337

Joined Sep 11, 2020
85
Thanks everyone I was testing the waters. Before I made this topic, my research implied the cost and complexity of this project to be beyond my means. I pay 7¢ kW/h for electricity so on that basis alone this project at the scale I was thinking is postponed. I will however purchase a small panel and battery for the purposes of learning and tracking trends.

#### MisterBill2

Joined Jan 23, 2018
8,744
Making decisions based on information does indeed have a lot of advantages over making random choices based on emotions or other non-solid suggestions from people who don't know.
Certainly a solar power project can be both expensive and complex. A very simple project can include a solar array of some size and a 12 volt battery to accept the charge. Charge control can be done manually, or some sort of control can be rigged to protect the battery. There are a lot of published plans for systems like that.

#### k1ng 1337

Joined Sep 11, 2020
85
Making decisions based on information does indeed have a lot of advantages over making random choices based on emotions or other non-solid suggestions from people who don't know.
Certainly a solar power project can be both expensive and complex. A very simple project can include a solar array of some size and a 12 volt battery to accept the charge. Charge control can be done manually, or some sort of control can be rigged to protect the battery. There are a lot of published plans for systems like that.
Besides temperature detection I charged NiMH batteries using lm317 and designed an overdischarge circuit. Doing this with a lead acid battery looks to be even easier and I've since learnt how to use temperature sensors. I have a 1w solar panel that I've ran a number of experiments on and it's immediately clear current is proportional to light intensity and I live in Canada so I am realistic on my expectations.

As you mentioned I did have to monitor the setup constantly as a backup for the basic over charge and over discharge implementations but that is part of the fun. I made this topic because the local classifieds I use always have solar panels for cheap, many are consumer grade but could be had for 20% or less the price of new and it would be interesting to see an array in action.

I also have dreams of building my own solar car and remote controls

#### MisterBill2

Joined Jan 23, 2018
8,744
Using "cheap" solar panels, or any other electrical things or devices, can indeed be a great cost aver, but it can alo be an "adventure" into rather dismal results. So it is very useful to understand quite well what you are getting.