PV Gap

Brandon Said:

What could I do with a 30 watt solar panel?

We Answered:

You would still need a charge controller and battery to store the power you generate, and an inverter to convert the DC power to AC that your PC needs. If you figure the panel could make 30W for about 5 hours, and you would have about 30% losses throughout the system, you could generate about 105 watt hours (wh) (30W x 5 hours - 30%). A laptop computer draws as much as 80W (newer ones use less), so if it ran for 1 hour, that would use 80wh. You could run it for just over an hour. You'd need about a 18 amp hour battery (105wh x 2 (you never want to drain more than half way) / 12 volts = 17.5ah).

Charge controller: http://www.altestore.com/store/Charge-Co…

battery: http://www.altestore.com/store/Deep-Cycl…

Inverter http://www.altestore.com/store/Inverters…

Susan Said:

How long does it take to charge a 12v deep cycle battery with a 10 watt solar panel?

We Answered:

a 10w solar panel means at peak efficiency ( high noon, panel pointed flat at the sun, hitting it at 90 degrees), you will get 10 watts (at any given second).

Watts = volts x amps

a 12volt battery needs an "incoming" current of at least 13 volts to charge it; 13.5 volts is better.

so if the output VOLTAGE of the panel is less than 13 volts it wont do anything.

Even if it is, 10 / 13.5 = .74 amp.( three quarters). It will take forever and a day to charge a deeply discharged deep cycle battery..........

consider that a small 110v battery charger is putting out 3-5 amps ( or 3 x 110 =330 Watts) and the alternator on a car is putting out 20 to 50 amps at 14 volts ( 280 to 730 Watts).

Victor Said:

Why is a charge controller not necessary for a 5 watt solar panel?

We Answered:

A typical lead-acid battery can safely be "trickle charged" at C/100 rate, where C is the capacity (if you are talking car battery, that is about 50Amp-hours typical). C/100 for a 50Ah battery is 500mA, so 350mA won't hurt it. The trickle-charge just overcomes losses due to battery self-discharge, which is fairly high in lead acid batteries. Your current is also limited by the internal impedance of the solar cell and diode.

On a small, 7Ah, 12V battery then, yes, you do run the risk of overcharging if you leave your solar panel connected because you will be charging at about C/20.

Leona Said:

How much money will I save with a 150 watt solar panel?

We Answered:

150 watt x 5.5 hours x 365days/year x 1kw/1000w = 301kWhr/year

301kWhr/year x $0.058 = $17.47/year


Hope that helps!

(5.8 cents per KWH is an awesome price! Where do you live?)