Prepper Forum / Survivalist Forum banner
1 - 20 of 38 Posts

·
Registered
Joined
·
2,478 Posts
Discussion Starter · #1 ·
Hi everyone,
As some of you know I did a post on Installing my first solar system. I kept it all 12 volts to keep
things simple. since then I have been experimenting with an inverter and every kind of 110 volt bulb
that I could get my hands on. I was really surprised at how long I can get a 110 volt bulb to run on
one 12 battery. So I'm thinking that I might add a little to the system and run some regular house
lights, computer, TV, and get the set up ready for a super efficient refrigerator that I might pick up
later. Now this might be a month or so before I even get started and I will do another post on this
project. (I want to get an independent water system done before I start this project)
Also I think I have found a way to pump the water out of my well and eliminate the storage for
huge drinking water using the solar setup.
So,, I would like to know would there be any interest in a post like this?
And if you have any questions or ideas on this it would be great to get some input and ideas now
I plan on tying in to the existing wiring at the fuse box and some help might be needed there.

And I just got a killer deal on two 235 watt solar panels they are for grid tie in but I have been spending
some time reading and talk to some experts on the phone and if it is done right with the correct inverter
they could be converted into two really strong off grid panels so I'm even thinking of setting them up as a
separate system for the heavy stuff. - just Kicking around some different ideas for now--
That's where you guys come on,,,, The appreciate all the ideas and help on the past project

Questions or input?
 

·
Mod Squad
Joined
·
2,262 Posts
Running regular bulbs is generally not a great idea. It's always better (cheaper & easier) to reduce consumption rather than just add more PV.

A 60 watt incandescent bulb obviously uses 60w, and wastes most of the power as heat. A compact fluorescent that puts out the same amount of light will use about 13w, and an LED light will use as little as 7w for the same light output. The LED light will also last for more than 20 years.

Anyway, I think having 110 AC is a good plan, even though you lose a few % in the inverter. I for one would be interested in reading about your project.
 
  • Like
Reactions: srtayl

·
Registered
Joined
·
1,368 Posts
Remember the formula: watts equal volts times amps

With this you should be able to get some ballpark capability. Remember all components have resistance therefore using the above calculation will be your upper limit but not achievable when used on large numbers of components in your circuit.
 

·
Registered
Joined
·
2,478 Posts
Discussion Starter · #4 ·
Running regular bulbs is generally not a great idea. It's always better (cheaper & easier) to reduce consumption rather than just add more PV.

A 60 watt incandescent bulb obviously uses 60w, and wastes most of the power as heat. A compact fluorescent that puts out the same amount of light will use about 13w, and an LED light will use as little as 7w for the same light output. The LED light will also last for more than 20 years.

Anyway, I think having 110 AC is a good plan, even though you lose a few % in the inverter. I for one would be interested in reading about your project.
Hi And thanks for your input,, Ok I have been reading and I see the same thing you are telling me.
But this is what I did I tried those energy saving bulbs from more than one place and some use more juice
than others even if they say the same on the box. I can start with just one battery and use an inverter and
run one bulb that is as bright as a regular 75 watt for 11 hours. Ands thats starting at 13.5 volts and only going down to 12.6 I found that quite surprising and impressive. My battery is a walmart [email protected] 12 volt deep cycle.
The inverter and bulb only pulls 1.2 amps that should be 144 hrs divide by 1.2 =more that I thought
 

·
Registered
Joined
·
2,478 Posts
Discussion Starter · #5 ·
Thanks and I have a request,, Can you post some more formulas?
I writing them down this time. Thanks for your help
"And thank you for not speaking techanize"
 

·
Mod Squad
Joined
·
2,262 Posts
The most important equation here would be P=IE, where Power (in watts) equals Current (in amps) times Voltage (in volts). From this, we can get I=P/E, which is saying that the amperage will be the wattage divided by the voltage. For example, a 100 watt bulb running at 100 volts will draw 1 amp.

The easiest way to see the savings is to look at it like this... if you are paying $1 per watt for panels, you would spend $60 to power a 60watt incandescent bulb. If you were using LED lighting and could get the same light output for 7watts, you would spend $7 for the panel, which is a savings of $53. The incandescent bulb costs $1 and the LED bulb costs $14, so the total of bulb and panel would be $61 (60+1) for the incandescent and $21 (7+14) for the LED.... roughly 1/3 of the cost.

But that's not the total picture. The incandescent bulb will need to be replaced about 20 times to match the life of the LED bulb. The incandescent will need more PV, so more mounting hardware, a bigger inverter, more batteries, and so on. In the end, it's not even close... go with the LED lighting.

The one thing that seems to be missing from your calculations is the amount of discharge on your batteries. You don't want to run them right down to nothing. If you want no more than a 25% discharge (fairly typical) and your battery is 114 amp/hours, you would be getting just over 28 hours of use at a 1.2 amp draw.

The cheapest place I have seen solar and wind equipment is at Northern Arizona Wind & Sun, where you can buy the solar panels for less than $1 per watt. I will be going with the SolarWorld SW-250 panels at about $1.10 per watt or the SW-265 at about $1.20 per watt because I like their guarantee. (they guarantee less than 0.7% drop in output per year for 25 years)

This is an interesting thread, please keep us posted!
 
  • Like
Reactions: srtayl

·
Super Moderator
Joined
·
9,218 Posts
One of the biggest mistakes made by people putting an inverter into a system is forgetting that it takes 10 times the amps out of the battery to go into the inverter compared to the amps on the label of the device being powered (actually a tad more). Example: you want to run a 120 volt fan, listed amps on the label is 1.3 amps; because the battery voltage is 10 times less (12 volt vs. 120 volts) the amperage consumed by the inverter is 13 amps (plus a little more for the inefficiency of the inverter). Years ago, before CPAP machines for people who have sleep apnea when they sleep, didn't operate on 12 volts DC, only 120 volts AC. A friend who tented with his boys every year a Boy Scouts wanted a way to run his CPAP in the tent. I went thru the whole explanation with him. When he went to Batteries Plus to buy the inverter and battery, the guy made the mistake above and sold him a small battery rated for 12 amps. He tried it out and over course it worked fine for the 5 minute test, but when he actually needed it, it ran for an hour and quit. He called me and gave me the data from the CPAP and I told him to buy a full size RV battery. Everything was fine then.
 

·
Registered
Joined
·
2,478 Posts
Discussion Starter · #9 ·
I hear what you are saying in every room I have SMD or LED bulbs in overhead fixtures.
They use next to nothing far as amp draw goes but I must confess that while they do the
job they just are not as a comfortable light as a standard bulb. The solar set I have seems
to have more juice in the batteries than I am using and I plan on adding another battery so
why not use it? If I run my lights a lot during the night by 11 or 1 o'clock the batteries are back up
to full charge. I can run two or three of the energy smart bulbs with a converter off of just the panels during
the day and not affect the charge in the batteries so why not use it? I meen I run a couple of
lights during the day just to keep the house from being too dark inside.
Right now I don't have a working amp draw gauge on my MPPT control box (sent back for warranty)
But what it takes to power one or two of the smart bulbs is not much.
I have a kill-a-watt meter and I'm ordering a lumens meter when I get everything I need I'll run some test
and compare what it takes to run the bulb --watts and amps--from house current and then see what it
takes to run it from a battery. Maybe it does take 10 times more power to run it that way.
And the inverter I am using right now is just an inverter I hope to soon have a "pure sine wave"
inverter I'm told they are a lot more efficient than a standard inverter.-we will see about that too-

The setup I have has got is all I will need when TSHTF. now I'm just tweaking it and seeing how far I can
take it. If I can run some lights, TV, computer, and other small stuff with a small investment why not?
 

·
Registered
Joined
·
2,478 Posts
Discussion Starter · #10 ·
----------------My findings so far---real world ---------------------------------------
Don't take this the wrong way I'm not here to argue or disagree with anyone I'm here to learn and share what
I find and learn,, My findings so far,,,,,,,,,,,,,
I had used a GE energy smart bulb 825 lumens (a little brighter than a standard 60 watt bulb) warm soft light #32700k
I ran the inverter from the control box rather than straight off the batteries to get a accurate reading on the amps.

On house current it pulled 13 Watts for just the bulb---------- 13 watts -divided by- volts 110 = .12 amps
Using the inverter and battery it pulled 1.4 amps.-------------- 1.4 amps x 12 volts= 16.8 watts

someone let me know if these formulas are correct------ So,,yea you're right about 10 times the amps
if the amps jumped up 10 times why didn't the watts go up as much? Or are my formulas incorrect?
 

·
Senior Member R.I.P.
Joined
·
2,886 Posts
The difference is the loss in the inverter. Some are more efficient then others. Ideally, 12VDC converted to 120VAC takes 10X power.

Solar panels don't care if their use is on or off grid. Its the inverter that determines on or off grid.

And you run into another issue with larger panels. Say you have a 200watt panel that is 24volts. A 100watt panel 12volts would produce about the same amperage.
 

·
Mod Squad
Joined
·
2,262 Posts
Your numbers seem about right to me. A watt is a watt, it doesn't matter where the power comes from. If you were on 120V main power, it will pull 1/10th the amps as the same bulb on a 12V battery because a watt is an amp times a volt. If one goes down, the other has to go up because the power stays the same.

120V X .1 amps is the same as 12V X 1 amp... 12 watts. Yeah, the current is 10X more with the 12V battery, but the voltage is 1/10th as high, so the power is the same.

If the bulb pulled 13 watts on house current and 16.8 watts with the battery and inverter, the difference is due to the inefficiency of the inverter, and the numbers seem to be in the ballpark to me. Your inverter probably also has at least an LED indicator light on it, this is using a little power too, and your ammeter is eating a little bit too. There's no such thing as a free lunch.

The GE Energy Smart bulbs are LED technology, and a good (but not the least expensive) bulb to use for solar applications.

I also agree that if you have the power, you might as well use it, but you did indicate that you were going to be adding refrigeration and maybe water pumping to your solar loads. Bottom line, it's always cheaper to conserve rather than add more batteries or panels.

By the way, although I do have a degree in electronics, I am not claiming to be an expert on batteries. As I understand it, the number of amp/hours in a battery depends in part on the discharge rate. As an example, the Trojan L-16RE-A is rated at 352 AH at a 20 hour rate and 360 AH at a 100 hour rate. This basically means you get more total power out of your batteries when you draw the power out more slowly.
 

·
Mod Squad
Joined
·
2,262 Posts
... And you run into another issue with larger panels. Say you have a 200watt panel that is 24volts. A 100watt panel 12volts would produce about the same amperage.
Right, because P=IE. To isolate the "I" (current, in amps) divide both sides by E; P/E=IE/E; the "Es" on the right cancel each other, so I=P/E meaning an amp is a watt divided by a volt.

So 200w/24v=8.33 amps, and 100w/12v=8.33 amps. At the same amperage, twice the voltage means twice the power.
 

·
Registered
Joined
·
2,478 Posts
Discussion Starter · #14 ·
Question about inverters,,, I been reading and watching videos about inverters and I see that there are
two main kinds. The standard modified inverter and the "Pure Sine Wave" inverter.

From what I have learned solid state electric motors (like in variable speed drills or fans) TVs, Computers, and
most electronics don't work well with the standard inverter. In more than one video using the standard inverter
I saw some of the motors made a buzzing noise and pulled more current. With the pure sine wave they ran smooth and
more efficient.

Has anyone ever used both to see what the difference was?

Also they come in all kinds of sizes 300 watt to 10,000 watt I was thinking of going with a 1500 watt
from what I have seen the smaller inverters use less than 1 amp to operate
Or has anyone have any input on the inverter information?
 

·
Mod Squad
Joined
·
2,262 Posts
Northern Arizona Wind & Sun's site has a good basic solar information site located at: windsun.com. They have an "Inverter Selection" page that walks you through all the different kinds of inverters and which are best for which application. Rather than just repeat what they say, (which is good, solid info), here's a link to that page... Inverter Selection
 

·
Senior Member R.I.P.
Joined
·
2,886 Posts
Pure sine wave inverter is always the best choice but also the more expensive. What you are going to run & duration dictates if you need pure sine wave or if modified is sufficient.

I happen to have a pure sine wave of 2,000watts as the primary 120VAC of my solar system. But also have a 1500watt modified sine wave. When I started out, I was given the advice that if it had a motor to use a pure sine wave but a modified is fine for everything else.

I've 120VAC angle grinders & they should be operated on pure sine wave but will operate on modified which I can tell they don't operate as well. However, I have an 18VDC cordless angle grinder & using modified for the battery charge is just fine as is charging the bateries for any of the Dewalt cordless tools I have.
 

·
Registered
Joined
·
2,478 Posts
Discussion Starter · #18 ·
Then I think I will just go with the pure sine wave,, It'd hard to tell what I might be running.
For now a computer, TV, along with a few lights. The inverter I have now is a yard sale 800 watt
I'll keep it as a backup for the lights
 

·
Registered
Joined
·
2,478 Posts
Discussion Starter · #19 ·
Another question about inverters,,,,
The inverter I used for testing stuff is a 800 watt and by itself with no load it didn't
take hardly any power to run. And I'm told that a 1000 or 1500 watt is the same way
anyone know for sure if this is true? I would spend a little extra and get one a little
bigger just in case I need it later if I knew it wasn't going to suck up too much electric.
 

·
Registered
Joined
·
2,207 Posts
They only draw as much current as you use + some basic power draw for the inverter so 1000 watts will draw the same from the battery with either a 1500 or a 4000 watt inverter.

The larger inverter may actually draw less amps
 
1 - 20 of 38 Posts
Top