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Solar Panel Sizes

Kelly Said:

What size solar panel do I need to power a meraki outdoor router?

We Answered:

You need something that will provide enough power to charge some batteries as well as run the router. This mean you need 12 w X 24 hours or 288 watthours of power. The solar panel needs to provide a minimum of 288 watthours of energy during daylight hours. Depending on where you live, calculate the number of hour of sunlight during the shortest day of the year. If you figure 6 hours of daylight as the shortest day, this means you need 48 watts per hour or 4 amps per hour if this is a 12 volt system. A common solar panel can deliver 1 amp so you would need 4 of them if that's the size you use. Remeber, this is a minimum. More capacity won't hurt.

Marie Said:

what size solar panel do i need to put on my 36v golf cart?

We Answered:

Hey Jessie, this is a great project you're on to. Does your cart have a roof or canopy already? Anyway, I'm guessing your cart has 6 batteries in it, probably Trojan T-105 or Exide golf cart batteries, is this correct? If so, they will be 220 amp hour, six volt batteries, wired in series for 36 volts. The only problem with your plan is you will not be able to do it with one panel, unless you can find one wired for 36 volt charging, which would be very rare. What you'll need is 3 panels, all the same size and output. Let's say you select a 50 watt panel, you have 3 of them, they are each designed to charge a 12 volt battery. Wiring them in series will allow them to charge a 36 volt battery. If the panels you buy have bypass diodes inside the junction box already (most of them do today), then all you need to do is mount them on the roof, wire them together in series, positive from the first panel to negative of the second, and so on, then the last two connections will be positive from the last panel, which you connect to positive on the first battery, and negative from the first panel, which will go to negative on the last battery.

Most solar panels are wired for 18 volts open circuit voltage, which is the voltage with nothing connected to them while they are in the sun. This voltage is necessary to charge a 12 volt battery. Don't make the mistake of thinking you can take 2 of them and make 36 volts, they will not charge the batteries at that voltage, you'll need at least 42 volts, preferrably more. Your panels must all be the same output, you can't use 2 40 watt panels and 1 70 watt panel. That would work if you were hooking them in parallel and charging a 12 volt battery, but in series, they won't get along.

Also, if you don't use panels any larger than 70 watts each, you will not need a charge controller. A rule of thumb is any charging source less than 2% of the battery amp hour capacity is considered a trickle charge, and it will be impossible to over charge the battery. One word of caution, if it's warm where you live, make sure to water the batteries at least once a month, they will go through lots of water during charging in warm temps. Just keep a couple gallons of distilled water around.

If you end up putting in a charge controller, then the diodes are optional. A diode is nothing more than an electrical check valve, allowing current to flow from the panel to the battery during the daytime, but not allowing it to go the other way at night. A charge controller will do the same thing. Also it's important to note that your regular charger, which plugs into the homes electrical system, will get along fine with the panel. You can park outside in the sun, solar charge, and plug in charge at the same time if you like, the plug in unit should shut down once the batteries are up high enough for the panels to take over. There's a great book at your library worth reading before you proceed, it's called, "The Complete Battery Book," by Richard Perez.

In case you're wondering, the reason we know all of this is we live in a solar powered home. Making your own electricity is like growing your own tomatoes, you end up learning all about bugs, soil ph, watering and sunlight whether you want to or not, it's a curse we have. Good luck, and take care, Rudydoo

Vicki Said:

what size solar panel would i need to power my aquarium pump?

We Answered:

I think what you need to do is go to your local garden store and look into "solar water fountains". There's probably something ready-made for the flow rate you want.

But if your hydroponics must have a reliable pumping schedule, then I'd say just bite the bullet and have an electrician run an outdoor outlet to the place you want.

Derek Said:

What size solar panel would you need to run a 120v motor 3.0amp?

We Answered:

Depends on how long you are running the motor. You will need to determine the load watt hours, and size it from there. 120V x 3A = 360W. If you run it for 1 hour, that's 360watt hours . If you run it for 10 hours, it's 3600 watt hours (360W x 10 hours). Once you have that number, put it in a off-grid calculator like this one, http://www.altestore.com/store/calculato… It will tell you what size solar array and what size battery bank you need.

You are also going to need an inverter to convert the DC voltage from the panels and battery to AC to run the pump. You'll need something that can handle the surge of the motor, so check out the specs. http://www.altestore.com/store/Inverters…

Thelma Said:

what is the average solar panel size for a 4 person family?

We Answered:

what are you wanting to do with it?
how big is your house?
where do you live?
more info please

Catherine Said:

What size solar panel needed to recharge a 12 volt deep cycle battery? PLEASE HELP?

We Answered:

The best place to ask this kind of question is the NAWS forum. There are true experts there, who enjoy helping with this sort of thing. You will need to tell them the amp-hours of your battery. They're at http://www.wind-sun.com/ForumVB/index.ph… .

Check with others in your area to see what is customary. It may be that a single battery is not enough to keep the tank from freezing over.

Also, the panel will work great at -40F, as long as you can keep snow and ice from blocking the sun on it. Sometimes the natural tilt of the panel is enough.

A lead acid battery, however, will not work at that kind of temperature. Presumably, you would have the battery in an insulated box that doesn't get so cold.

Annie Said:

what size solar panel should do i need,?

We Answered:

Well first you need to select a suitable pump and filter for the area you wish to cover, then check their ratings. You need to know operating voltage and consumption or wattage.
Then follow the guidelines on this website: http://www.solarpanelinfo.com/

It's not really a question of voltage but one of power consumption, or wattage. This is why you need to work out the requirements first. Select a pump which can satisfy the requirements then check that pumps rating. It should tell you Voltage, Current and Wattage, Voltage and wattage being those that concern you. Once you know that you can decide on what arrangement of solar panels you need.

I would start by doing a google search for pumps then comparing different pumps with different voltages/wattages.
Then you could check this site: http://www.fvgenergy.com/photovoltaic_eng/photovoltaic_module_10-50w_en.html
to get an idea of what panels you will need.
Say for example you find a 12v pump at 50w then you will need a solar panel of 12v/50w. If you find you need a 240v pump then you may need to buy several lower voltage panels and connect them in series.

Discuss It!

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