I have a few questions about solar panels and batteries.
1. looks to me that 60 watt solar panels are the most common and cost efficient. I know that a 60 watt panel produces 60 watts of power at 12vdc. lets say i have five hours sun on the panel. how long would it take for a 60 watt panel to charge a standard 12 vdc battery from basically dead to full charge. I know it depends on the type of battery, but let’s just call it a standard car type battery. looking for just general info not exact science info.
2. if one panel is capable of charging one battery in less than 5 hours of sun. how many batteries can it charge completely in 5 hours of sun?
3. using a 12 to 120 volt power converter to get 120 volts from a battery how many watts of power are you able to pull from a battery before the charge is to low to be usable without a recharge. again, i know there are variables to take into consideration, but i’m looking for just general answers. like for example, "X" watts of use for"X" hours.
4. I assume a 60 watt panel is a 60 watt panel? meaning, all 60 watt panels are made equal, they basically all produce basically the same amount of power with basically the same efficiency.
5. with a solar panel is it better to catch the morning sun or afternoon soon or does it matter? I know the more amount of sun you catch, the better.
6. in order to take advantage of the tax credit, do you have to use a professional installer or if i buy the panels, converter, batteries, etc, myself and install myself can i claim the tax credit?
1. A 60 watt panel produces 12 vdc @ 5 amps at maximum sun. Realistic power is about 70% average throughout the day. So, your output will be about 40 watts. Take a battery with a reserve rating of 120 minutes. That is it will take 120 minutes for the battery to drop to 10.2 v when discharged at a constant 25 amps. That’s about 250 watts in two hrs. To recharge the battery, you have to place back 250 watts in 2 hrs (not realistic – battery hurt). But 40 watts recharge will take 12.5 hrs to recharge the battery.
2. Can’t answer. How much less than 5 hrs? But a 60 watt panel won’t recharge the battery in 5 hrs.
3. Inverters are only about 75% efficient (depending upon design). Usually, when battery power drops below 10 volts, the inverter shuts down. And that would depend upon reserve capacity of the battery and how much power you draw from the inverter. A 120 minute reserve capacity battery with a 75% efficient inverter gives you 90 minutes at 300 watts (12 v @ 25 amps).
4. Any assumptions about this item makes all other calculations unuseable.
5. The sun at high noon is the brightest – less atmosphere to scatter the sun’s rays.
6. The tax credit only applies if you have it professionally installed and tied to the electrical grid. It may also apply to 100% off-grid systems. It does not apply to self-installed units. Our utility will not permit self-installed solar systems to be tied into the grid. Yours may.
you get 60w from a 60w panel only when the sun is bright directly on it, since the panel will be in a fixed position you will not always get 60w. This fact makes the remainder of your questions not worth while.
Solar panels are not all made the same, its the build quality and efficancy that differ.
The truth is that unless you live somewhere that is sunny all day everyday, the cost of solar panels, the batteries, and the controls the pay back is not worth it, which is borne out by the fact you dont often see it being used.
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Look online for free amperage battery charging calculators. If a 60 watt panel produces 3 amps for 5 hours then that should be 15 amp hours placed in your battery. Its probably less but with losses and charge controllers which must be used.
While its right that the panels may take six to eight years to pay for themselves they then be producing free electricity for the next ten to fourteen years by warranties I’ve seen.
Ten years times 2,000 bucks a year isn’t terrible. 20,000 in free electricity. And, you don’t pay increases or distribution charge and may be able to sell some back.
The utilities don’t want this probably but its a free country.
It will be a part of Americas energy future. It won’t be entirely coal, oil, gas, nuclear, wind, biomass, hydrogen and water power.
I like them since they’re on NASA sattelites in space and that there are no moving parts. Just crystals like the New Agers like. I want the extra 150 a month I spend on electricty for other things.
Look at it this way. People buy new cars which are in the junk heap in five to ten years. These cells are similar price but last 10-25 and if you oversize then 30.
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The calculations you question for are moot, as you don’t provide information on how much sun hours you get and how much cloudy or partly cloudy days you have. If you use the above mentioned calculators and factor in the actual sun that will give you an answer. All panels are not equal, and are rated differently, check with the manufacturer. The Tax credit is a sweetener, its not worth paying for the solar system simply to get that.
But, let me say that I have solar electricity and hot water panels on all my houses. They face the arc of the suns travel, so receive sun all day, cloudy or not. I have not paid for electricity since installation and get my water heated for free using solar power. I also SELL excess power back to the state grid through an inverter. Doing so means my system has paid for itself in just under 4 Years and been making a profit for last 3 years. You have to consider the initial installation costs and be aware that saving on cheap components, such as smaller panels, cheap batteries or even cheap mild steel mounting brackets will cost you more when they have to be replaced earlier. Go for reputable well manufactured brands and look around your area, see who is using what. Talk to owners about any issues they have had. It’s worth every penny, to me. It might not be as much for you. Oh and as for saying its proved in how small they are used…well power companies want you hooked up to their grid, so you pay for all their decisions. Including the exec perks and bonuses.
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been there, doing it
Kirraina is right
The only thing I can add is buy the best, once. If you buy second or third best it won’t be long until you have to buy it again.
Something I read a long time ago, and it still makes sense today- Do you know why the rich are rich? they only but something once! EG. a excellent refrigerator will last 30 years, a piece of junk 5-6 years. A excellent fridge is not 5 X more money than the cheapest one. Therefore which is the best deal?There is one other consideration, new Technologies, Try and find something that is easily upgradeable.
PS forget about car batteries they are not built for solar systems. You must use proper deep charging batteries. Sorry, yes they are expensive as well.
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1. A 60 watt panel produces 12 vdc @ 5 amps at maximum sun. Realistic power is about 70% average throughout the day. So, your output will be about 40 watts. Take a battery with a reserve rating of 120 minutes. That is it will take 120 minutes for the battery to drop to 10.2 v when discharged at a constant 25 amps. That’s about 250 watts in two hrs. To recharge the battery, you have to place back 250 watts in 2 hrs (not realistic – battery hurt). But 40 watts recharge will take 12.5 hrs to recharge the battery.
2. Can’t answer. How much less than 5 hrs? But a 60 watt panel won’t recharge the battery in 5 hrs.
3. Inverters are only about 75% efficient (depending upon design). Usually, when battery power drops below 10 volts, the inverter shuts down. And that would depend upon reserve capacity of the battery and how much power you draw from the inverter. A 120 minute reserve capacity battery with a 75% efficient inverter gives you 90 minutes at 300 watts (12 v @ 25 amps).
4. Any assumptions about this item makes all other calculations unuseable.
5. The sun at high noon is the brightest – less atmosphere to scatter the sun’s rays.
6. The tax credit only applies if you have it professionally installed and tied to the electrical grid. It may also apply to 100% off-grid systems. It does not apply to self-installed units. Our utility will not permit self-installed solar systems to be tied into the grid. Yours may.
References :
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