[falm16]

i bought a few solar panels, harbor freight, 3 seperate 15 watt panels with a cheap looking control box. 1 panel has broken glass but still reads on a meter it's producing almost 24 volts, same as the others. i have all 3 panels hooked together, total of 45 watts, going into the "box" that shows the system is charging and everything is good, this is all hooked up to 3 large deepcycle batteries. i have a remote cabin in north arkansas, not trying to run the cabin, just store enough juice to watch TV and run a fan and a couple of those low wattage light bulbs. the panels do not seem to keep the batteries charged enough, can run maybe 2-3 hours. have cut a couple of trees trying to maximize solar exposure, doesn't seem to help. am i asking too much of the 45 watts to try and charge 3 batteries in a days time? i'm using a 4000 watt invertor, it shuts the system down at about 11.5 volts remaining. anything i can do to help?

 

[falm16]

SOLAR.

 

[Packrattusnongratus]

I have questions about the same setup. What book would help me in the absence of lots of answers from experienced folks? Thanks. Packy

 

[AmmoSgt]

i bought a few solar panels, harbor freight, 3 seperate 15 watt panels with a cheap looking control box. 1 panel has broken glass but still reads on a meter it's producing almost 24 volts, same as the others. i have all 3 panels hooked together, total of 45 watts, going into the "box" that shows the system is charging and everything is good, this is all hooked up to 3 large deepcycle batteries. i have a remote cabin in north arkansas, not trying to run the cabin, just store enough juice to watch TV and run a fan and a couple of those low wattage light bulbs. the panels do not seem to keep the batteries charged enough, can run maybe 2-3 hours. have cut a couple of trees trying to maximize solar exposure, doesn't seem to help. am i asking too much of the 45 watts to try and charge 3 batteries in a days time? i'm using a 4000 watt invertor, it shuts the system down at about 11.5 volts remaining. anything i can do to help?

You don't say what the amp hour is on the batteries... Large deepsycle??? lets guess and work with 100 amp hour each @ 12 volts for a total of 300 amp hours. you input is 45 watts at 24 volys or about 2 amps.. ( less actually, 48 watts at 24 volts is exactly 2 amps with no line loss ect) ... all of which equals 300 /2= 150 hours of charging assuming you average 5 hours of usable sunlight per day ( thats about the North American average and probably good for North Arkansas and assuming you have no shade issues . should take about 15 days to charge up 300 amp hours of batterise with your rig.
On the using end your inverter is using about 25% of your load just by itself .. lets say a 100 watt bulb at 120 volts is about one amp per hour but adding in the inverter you draw 1.25 amps per hour.... if you are going to run off batteries you save big money ( in systems costs) running 12 volt DC appliances and not using an inverter.

With that big of a bank of batteries ( and I am being conservative on the batteries because "big deep cycle" could very easily be 200 amp hour each and 20 days to charge).
Regular car batteries are 40-80 amp hour and a "trickle charge" type solar panel is about 5 watts just to keep the battery fresh in a car... so 40 amp/h is to 300 amp/h like a 5 watt panel is like a 40 watt panel... your solar panels are just a tad over a trickle charge concidering your battery bank..

My recomendation is , if you have wind and a hill to concider one of those 400 watt wind generators that go for about $1500 complete with pole and guy wires... sportsmansguide had them for a while .. they are around out there $700-$800 for the generator head and $700-$800 for the mast and accesories... and run it with your solar panel... typically you can get solar panels in moderate sizes .. 30 watt give or take for about $7 a watt with all the needed accesories so that $1500 will only get you about 210 watts.
You have to look at local conditions when you buy your gear.. a 200 watt panel with 8 hours of sun is the same as 400 watts of wind if you only get 4 hours of usable wind a day. Different wind generators and different manifacturers set up their wind generators to be optimum at different wind speeds .. wind generators that crank in a light breeze cost more than ones that only crank over 10 mph.
The cheapest route is , if you have one of the cheap controlers that will handle about 100-105 watts is just to max that controler out at whatever it is rated and get some cheap 12 volt lights and a TV and fan that will run direct ( not thru a transformer or inverter) on 12 olt DC... thats maybe abother $200 in panels and a couple hundred for the lights and appliances ( assuming samll portable B/W TV).
Good luck.
You also probably lose some efficency running 24 volt panels into a 12 volt bank, but not enough to really get worried about.
Another system killer is having an old battery in a bank of newer batteries.. that is a biggy.. if you buy batteries get them all at the same time and change them out all at the same time. Also use the same type of battery thru out your battery bank amp hour and voltage and all the same construction dry cell or wet cell or gel or whatever.
Make sure your charging rig does not allow the batteries to drain thru the charging rig when they are not charging.. some of the really cheap controlers don't protect against this.

 

[falm16]

great info, thanks. my panels are 12v, but when you put a meter on them it shows they are putting out 24. have no idea about the amp hour of the batteries, they are new fairly large deepcycle. i knda thought the panels were about equal to a trickle charger, and yes, the controller is CHEAP. gots lots of pretty litttle LED's but is a china made thing that came with the panels, i suspect it does let the batteries discharge although in the owners booklet it states it does not. i do have shade issues, just cut 2 trees and need to cut 1 more, ireally hate to cut shade trees by the cabin but i realize it is necessary. AMMOSGT, 1 more question. i have a 1000 watt gas generator, a cheapie, that has the connections to charge a battery, it uses premix, but the little thing will run for 6-7 hours on a gallon of gas..... my question is, can i hook this up to the batteries, run the generator to hold them up, and at the same time run my invertor to power the cabin, this seems to be the way to go when i need to run saws and such without draining the batteries. thanks again. i'm electrically illiterate.

 

[AmmoSgt]

I don't know... depends on the equipment, input voltages, voltage regulators, how you have it rigged up, ect.

Batteries , as a general rule, are pretty tolerant about voltage issues as long as it is DC power, and the input is above a certain threshold voltage wise for charging. As an example the whole Jericho TV show thing with the wind generators and needing some sort of speed regulator so the voltage is "correct" only applies if they are NOT using batteries and running the wind generators directly into a inverter to power the town. IF they have batteries to run into the batteries will act as a "filter", taking in any voltage over threshold and storing it and then putting out the batteries rated voltage into an inverter. It would be nice to have a voltage regulator ( off a car, or better a heavy duty regulator off a truck or the like to smooth out the input and prevent feed back ) but not a critical item. Of course if they used real world stuff in Jerchio then they wouldn't need to interact with New Bern at all, and there goes the plot.
Read the inverter manual and see what it says about running it while the batteries are being charged and if you need a voltage regulator between the batteries and the inverter to protect the inverter.
Likewise you might need to protect your panels from current flowing back up into the panels, this is one of the things the panel regulator/controler is supposed to do, so read and see if it says anything about that...personally I would disconect the panels at night and use the generator with the panels disconected to charge the battery if I didn't know for sure about the batteries discharging when thru the panels when the sun wasn't shining ect.

The batteries should be marked with voltage and amp hour rating somewhere on the case.

the simple fact of any system is you can get more out than you put in... if the panels are rated at 45 watts and you have 5 hours of sun then you can use maybe 150-180 watts a day if you want to maintain the batteries at full charge( you lose some watts in the charging process as heat , batteries and wires all get warm from the missing watts).

That shade issue is critical as is the orientation of the panels. Look at it this way , lets say you panel is 8" x 12" for example. Now imagine a 4" x4" square of light shining down on the panel directly square on the panel. Now imagine moving that light source to one side so the panel is at an angle and the light spreads out, still 4" wide but because of the angle covering the whole 12" long lenght of the panel ( try this with a flash light so you can visulize it better). when the light is 4"x4" straight on to the panel it only cover 1/6th of the panel and makes, lets say, for example, in this case 4 watts and the panel can potentially convert that light , if each of the possible six 4" squares had the same light, into 24 watts..... but at the angle where the light covers a 4" x 12" section of the panel you still get 4 watts from the light, but it now takes half of the panel, making the panel potentially capable of only 8 watts with angled light. Throw in an inverter that sucks up 25% of any power coming thru it converting it to AC and you only get 6 watts into the light bulb by the time all things are said and done.

Okay now about that generator , undoutablely that 1000 watt rating is the 120 volt AC output rating. Divide the volts ( 120) into the watts (1000) and you get amps + about 8 amps. I suspect that in DC mode ( battery charging mode thru the DC connector for the battery cables on the generator) you are still getting about 8 amps. Amp hours are the unit of storage/ measure of electrical power, watts are quanity and volts are "pressure" .
http://www.powerstream.com/Amps-Watts.htm
You can't get something for nothing. Your 45 watt panel at 24 volts is about equal to 225 watts at 120 volts , or put another way 200 watts of solar at 24 volts equals your 1000 watt generator at 120 volts. Anyway you cut it it takes about 1 horsepower of gasoline engine to make 500 watts at 120 volts or 4 amps. Those small electrical chain saws for example can run as high as 13 amps with intial startup requirements lose to 30 amps for a very brief moment( high start up draw is a characteristic of electrical motors). That why gasoline generators are often rated something like 1000 watts/1800 surge watts. Doesn't mean it actually out puts 1800 watts , just means that a short draw of 1800 watts won't fry it and it will take a moment for the electrical motor it is powering to get up to speed.

 

[falm16]

i was planning on disconnecting the panels if i use the generator/batteries/invertor setup. the manual says nothing about this type of setup. i am running a 12 volt system, it's just the panels register around 24 volts output when i test them. i think the shade is killing me, will work on that, and also try and boost my panel bank, i'd like to try at least 45 more watts.... i really just want to run some lights and a fan or two at the cabin, when i need more power to work, i have a 4500 watt, a 2800 watt and the 1000 watter, but i'm trying to get away from gasoline as much as possible. the info you give me, AMMOSGT, bogles my mind, wish i knew as much as you. thanks.

 

[cujet]

The solar panels are too small for any practical application other than keeping a backup battery charged. In the brightest sunlight, all you could expect to run is about a 35 watt load. Much less as soon as the sun is not direct!

There must be NO SHADE of any sort anywhere on the panels when they are producing power. Even a stick will kill the output! Solar panels need full light. You cannot have a corner of one panel shaded and get any power out of that panel.

Also, 24 volts is just a bit high for open voltage on a 12v solar system. 18 would be better. It is likely that you are not using all the watts the panels are capable of. Remember amps x volts = watts. Each solar cell can only make a certain amount of Amps.

Example, 1 amp at 12V is 12 watts. 1 amp at 24 volts is 24 watts. Your solar panel would likely make less than it's rating in your situation.

Chris

 

[cujet]

Charging tbe batts DIRECTLY via the generator's 12V output is OK at any time. You can leave the solar panels hooked up, along with the inverter (as long as it does not cut off at 14V). One really cool situation is to use a Honda 1000W suit case generator. It varies the speed depending on load, so it will use less gas.

In your situation it would take 40,000 years to save enough gas with that tiny Honda to offset the purchase price though!

Chris

 

[19thMtBn]

For your light try using 12v LED lights. They draw a tiny fraction of other type lights.
I got free advice and bought my panels for my remote cabin from http://www.readymaderesources.com/ Their store is co powered with solar & wind. These people have a lot of real world day to day experience with solar and wind. I told them what I wanted to do and am very satisfied. Several years ago I bought from a place that sold me stuff that was near useless for my purpose and wasted my money.

The other post about the shade killing your output is very true. I also had to cut trees ,consider the change of seasons. I had to cut several more trees to eliminate the shade in fall & winter.

Red Woods

 

[falm16]

thanks for the advice, i have cut a couple of trees, need to cut a couple more, boy i hate to do it, though. i have 3 15 watt panels from harborfreight, and a 15 watt fold out i add if not using it somewhere else, trying to keep 3 deepcycle batteries hot enough just to watch TV and power lights in the cabin at nite. not there a whole lot so i've not invested more time/money into more equipment. the little 1000 watt premix generator will run 7 hours on a gallon or less, running lights, fans, and tv, so it's great, but i like to avoid the noise if possible.