PV Gap

Julie Said:

Can you connect a solar panel to a regular plug, using copper wire?

We Answered:

The 1st half of the question is a bit confusing and more info is needed to answer the question.

I will address the "confusing I know" statement.
If your goal is to hear the sound of D/C electricity being generated in a solar panel, the speaker should emit a steady hum or buzz. Be certain before you connect the 2 together that the output of the solar panel does not exceed the input of the speaker.

If on the other hand, your goal is to actually power a sound system such as a car radio (which runs on D/C the same as the solar panel out put), You would need to know the radio voltage input ( from the label on the back of the radio) and make sure the output from the solar panel matches the radio input. The odds of the 2 values matching are quite small which means you would need to implement a step up or down transformer, and/or a voltage divider .. Unless you have electronic know-how, I strongly advise you get help.

If your trying to power an A/C system (household voltage), DONT! The 2 voltages are incompatible. Household voltage is potentially lethal!

Hope this helps. Feel free to post any questions you may have at http://www.solarmandan.com.

Steve Said:

Solar panel wiring, materials?

We Answered:

You need to have some idea of what power you need or you will most likely be disappointed.

Batteries rated at 100Ah can deliver about 20A for a few hours. This corresponds with 240W ber 12V battery, so you can say after losses, 200W of AC. If you wish to power 200W or less, that is fine. If you want more, you need more batteries. It is best to connect them in series for 48V or something like that. This keeps the current in the more practical 20A range, and the cables are smaller and cheaper.

When it comes to charging the batteries, the larger panels are around 100W panels. These deliver a current of about 5A to charge the battery. This is the peak, when the full sun is at right angles to the panel and high in the sky, so delivering about 1200W/m^2.

Let us say that there are 5 hours a day equivalent full sun. You can look up your region on the internet in most places. That gives 25Ah per day. That is all you can hope for with one x 100W panel per day.

If you have more than 12V in the battery, you will need a panel for each 12V of the battery, so that is 4 panels minimum for a 48V battery.

As there are only 25Ah from a panel per day, and it takes 1.4 times the Ah to recharge the batteries, we can expect to take 6 days to recharge a 100Ah battery that is not being used. This can be improved by having more solar panels. Thus 8 panels would produce 50Ah per day for a 48V system (to charge in 3 days). As you can see you have to work out a usage pattern for your electricity that suits the limits of your panel string.

Other things you need:
The cable size must be big enough to carry the current safely. It will most likely need to be bigger again to minimise the voltage drop. That depends how long the cable is. Generally it should not exceed about 5m, and that probably means the next size up in cable. You can check all this from cable suppliers tables of resistance per meter and current carrying capacity. There are 2 main cable sizes. The cables connecting solar panels together and to the battery. In a series chain this should be 10A cable (for 5A panels) or larger to minimise voltage drop. If there is more than 1 series chain, wire each string separately to the charger where they are commoned together. The cable from the charger to the battery needs to be bigger to suit the added currents of more than one string.

The other cable size is from the battery to the inverter. It should be at least big enough for the maximum current the inverter can draw. This should be 20 or 30 Amp cable considering 100AH batteries. It should be larger so that the voltage drop through both cables is less than 1% overall. Don't skimp on this. Take the next size up if in doubt. The load side of the inverter is 120/240V AC so leave it to an electrician to make sure it complies with regulations.

Charging control:
A solar charger connects between the panel string and the battery. It needs to suit the maximum current from the panels, as well as the voltage of the battery. If you get an MPPT charge controller that is better. It adjusts the charge current to maximise the power obtained from the panels as conditions change. I think an ammeter for charge current is a good idea. This can be in series with the charger and the battery. A ten amp meter will suit for a single string, ec.

Safety:
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The solar panel side of things doesn't need a fuse because the panels are inherently current limited to less than the cable can carry, by their nature. Between the charger and the battery should be a fuse, mounted near the battery. It is rated to the cable size, so if you have 20A cable, 20A fuse. The reason for this is that the battery connects to the charger, so if you short something in the charger the battery current is there to make a fuse necessary.

There must be a fuse between the battery and the inverter. There may be some sort of battery fuse in the inverter. This fuse prevents a fire if the inverter should fail. It is rated to the inverter maximum current, or allow a little more for surges. It should not be higher than the cable current rating.

If you connect an ammeter (rated for max inverter current) between the battery and the inverter, it will help you determine what is happening with power consumption. Alternately, have an ammeter in the AC distribution side.

If you have sufficient power (like 1kW or more) you can consider a grid tied system , that uses no batteries. You need to get that done professionally anyway.

The batteries need to be located outside in a well ventilated situation.
Solar panels need to be well ventilated. Allow fre air around the back. The inverter and charger also need good ventilation for cooling, and should not be in the sun ever. Obviously electrical parts are protected from the weather, vermin, ants etc.

Alex Said:

If a solar panel is rated for 5 volts, does that mean that it will never achieve higher?

We Answered:

Have you considered using a small battery in between the solar panel and the IPOD? That would prevent the IPOD from having to absorb voltage spikes from direct power from the panel.

A solar panel's rating is at standard testing conditions - laboratory conditions. Therefore it is possible that the panel will output more than (and certainly less than at times) the rated output. Take that into consideration when charging the IPOD.

They are making some small solar panel set ups for charging portable electronics.
Good luck!
Kristen
http://newenglandbreeze.com/

Amanda Said:

Solar panel wiring trouble.?

We Answered:

Wire in series voltage is additive

There are three types of wiring configurations that are relatively easy to learn. Once mastered, the job of wiring batteries or solar modules becomes easy as pie. The three configurations are:



Series wiring



Parallel wiring



And a combination of the two known simply as series/parallel wiring.



In any DC generating device such as a battery or solar module, you will always have a negative (-) terminal and a positive (+). Electrons or (current) flows from the negative terminal through a load to the positive terminal.



For ease of explanation we shall refer to a solar module or battery as a "Device"



Series Wiring



To wire any device in series you must connect the positive terminal of one device to the negative terminal of the next device







Important: When you wire devices in series the individual voltages of each device is additive. In other words if each device in the above example had the potential of producing 12 volts, then 12 + 12 + 12 + 12 = 48 volts. If these devices were batteries then the total voltage of the battery pack would be 48 volts. If they were solar modules that produced 17 Volts each then the total voltage of the solar array would be 68 volts.



The second important rule to remember about series circuits is that the current or amperage in a series circuit stays the same. So if these devices were batteries and each battery had a rating of 12 Volts @ 220 Amp hours then the total value of this series circuit would be 48 Volts @ 220 Amp hours. If they were solar modules and each solar module had a rating of 17 volts and were rated at 5 amps each then the total circuit value would be 68 volts @ 5 amps.



In the example below two 6 Volt 350 Amp hour batteries were wired in series which yields 6 Volts + 6 Volts = 12 Volts @ 350 Amp hours.







If the above devices were solar modules which were rated at 17 volts each @ 4.4 amps then this series circuit would yield 34 volts at 4.4 amps.



Remember the Voltage in a series circuit is additive and the Current stays the same.





Parallel Circuits



To wire any device in parallel you must connect the positive terminal of the first device to the positive terminal of the next device and negative terminal of the first device to the negative terminal of the next device.







Important: When you wire devices in parallel the resulting Voltage and Current is just the opposite of a series circuit. Instead the Voltage in a parallel circuit stays the same and the Current is additive. If each device in the above example had the potential of producing 350 Amp hours then 350 + 350 = 700 Amp hours, the Voltage would stay the same.



If these devices were batteries then this parallel circuit would yield total voltage of 12 volts @ 700 Amp hours. If these devices were solar modules that produced 17 Volts @ 4.4 amps each then the this parallel circuit would yield 17 Volts @ 8.8 amps.



In the example below four 17 Volt @ 4.4 Amp solar panels were wired in parallel which yields 4.4 Amps + 4.4 Amps + 4.4 Amps + 4.4 Amps = 17.6 amps total @ 17 volts







if the above devices were batteries which were rated at 12 volts each @ 220 Amps hours then this parallel circuit would yield 12 volts @ 880 Amp hours.



Remember the Voltage in a parallel circuit stays the same and the Current is additive.



Series/Parallel Circuits



Hold on to your hats because here's where it gets a little wild. Actually you've already learned all you need to know to under stand series/parallel circuits.



A Series/parallel circuit is simply two or more series circuits that are wired together in parallel.













In the above example two separate pairs of 6 Volt batteries have been wired in series and each of these series pairs have been wired together in parallel.



You might be asking why in the world would someone want to put them self through this ? Well lets say that you want to increase the Amp hour rating of a battery pack so that you could run your appliances longer but you needed to wire the pack in such a way as to keep the battery pack at 12 volts, or you want to increase the charging capacity of your solar array but you needed to wire the solar modules in such a way as to keep the solar array at 34 volts, well, series/parallel is the only way to do that.



Remember in parallel circuits the current is additive so thus you increase your run time or Amp hour capacity or in the case of solar modules, you increase your charging current by wiring the batteries or solar modules in parallel. Since we need 12 volts and have 6 volt batteries or in the case of solar modules we need 34 Volts and have 17 Volt modules on hand on hand, wiring the batteries or solar modules in series allows us to get the 12 Volts or 34 Volts that we need.



An easy way to visualize it would be to start by wiring the batteries in individual sets that will give you the voltage that you need. Lets say that you need 24 volts but have six volt batteries on hand. First wire four of the batteries in series to get 24 volts. (Remember wire in series to increase the voltage) and continue to wire additional sets of four batteries until the batteries are used up.



Next wire each series set of four batteries in parallel to each other (Positive to positive to positive and so on and then negative to negative to negative and so on) until each series set is wired together in parallel. If each series set of batteries equals 24 Volts at 350 Amp hours then five series sets wired to each other in parallel would give you a 24 Volt @ 1750 Amp hour battery pack.



Remember: In a series circuit the current stays the same but the voltage is additive. In a parallel circuit the voltage stays the same but the current is additive.