PV Gap

Regina Said:

Can solar panel and wind turbine generator system run continuously for 6 month or longer?

We Answered:

Well unless you have daylight and wind continuously for 6 months the answer is no.

Patrick Said:

I'm building a solar panel (70-100 Watts) and i don't know what size battery makes sense to use?

We Answered:

Generally, the larger the battery, ie, the amp-hour rating is higher, the better you are, as you can store more energy. So it's a trade-off of capacity versus price and size. You have to decide that trade-off, you know the parameters, I don't.

You may want to get a battery rated for deep discharge. Most lead acid batteries (auto type) cannot be completely discharged without damaging it. These are sometimes referred to as "marine batteries".

100 amp-hour is about the biggest, and your 100 watt panel will take about 12 hours to charge it.

You will need a panel output of 15 volts in order to charge a 12 volt battery, 12 volts is not enough.

You will also need a charge controller of some sort to avoid overcharging the battery and damaging it. A good one will use a DC-DC converter to increase the voltage to that needed to charge the battery.

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Holly Said:

is my solar panel big enough?

We Answered:

A solar panel is a DC device, you so want DC voltage.


I don't think your panel is big enough: milliAmps are THOUSANDTHS of an amp, not hundredths. So 83 mA = 83/1000 = 0.083A, ie your power is 3.403 watts rather than 34.03 watts.

To get a 30W output in good sunlight you'll typically need a panel area that's equivalent to about about 50cm x 50cm.



Car batteries are apparently about 1kWh:
http://mb-soft.com/public2/storing.html

So even if you had 30W, you'd need to run it for 1000/30 = 33 hours in good sunlight. So it won't do a great job.


The reasons for the tiny output will probably be the small surface area (normally people cover whole roofs in solar panels and that way you get sensible power output), and because yard lights are cheap, so have cheap solar panels made from the cheapest amorphous silicon they can get their hands on - so they're not very efficient either!