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I have recently purchased a solar powered gable fan for my attic. This fan will only work when the sun is up, but I would like a little more out of it during the early evening hours (no sun). Is there a solution where I can purchase a battery that will be charged by this solar panel, while working the fan, and get a little more juice during the evening hours? If so, how can I calculate which battery I need and where to purchase? Thanks in advance for your answers.

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    If it doesn't have a battery circuit built in then chances are no. There likely isn't any leftover current to both run the fan and charge the battery. There are models with built in batteries designed for this. – Tyson Jun 28 '16 at 15:47
  • What's the make and model of the fan? – Tester101 Jun 28 '16 at 15:53
  • More info needed, Voltage of fan motor, amperage consumed at full power. At that point, if it runs at a common lead-acid cell voltage, you can start figuring how many extra panels will be needed to fully charge the number of batteries needed for your extended run plus run the fan. You will need a charging regulator that cuts off power to the fan so the batteries maintain their safe minimum charge. The batteries cannot be depleted by the post-sunlight run, they must have charge left so they don't get damaged. – Fiasco Labs Jun 28 '16 at 19:20
  • Air Vent 17.875-in Dia Solar Gable Vent Fan – Keep It Moving Jun 28 '16 at 19:41
  • It's from Lowes and the Q&A on the site is suggesting that it pulls 24 volts – Keep It Moving Jun 28 '16 at 19:44
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You need to describe the power/amperage of the motor that runs the fan.

In any case, the answer is that you would need quite a big solar system to run the typical attic fan. A typical 20-inch high velocity fan uses about 2.5 amps. So, to run the fan for 4 hours would requre 10 amp hours. A large, roof-type solar panel produces about 5 DC amps and you will need about 30 AC 110V amps to run the fan, so that would mean you would need about 6 large solar panels, a charging controller, a 150-amp hour battery, and an AC inverter.

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    This is a 17" gable fan, not a large topside roof fan. I was wondering if there was such a thing as a battery I can attached to this to continue running after the sun goes down. The panel is not that big and may only be enough to run the fan and not additionally charge a battery while running the fan. – Keep It Moving Jun 28 '16 at 19:48
  • So I installed it last night and it was cloudy and rainy; so the little bit of light left did not power it at all. This morning, had to leave to work before sun actually made it over the trees. Can't wait to see it work. – Keep It Moving Jun 29 '16 at 12:29
  • Keeping in mind that the highest solar heating will also be at the time of highest solar power for your fan, it sounds like you are "right-sized" with what you have. Sure you could spend a bunch and build a mini solar power station, but in the end it wouldn't have enough extra effect to be worth it. When the fan is not powered you still have the opening for ventilation. Have fun! – SDsolar Apr 1 '17 at 5:25

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