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Solar Powered Vent for my Trailer

rbsWELDER

rbsWELDER

Active Member
So I would like to add a powered vent to my trailer, and I would like to make it solar powered. This should eliminate the need for a thermostat to open & close the vent.

The 12 volt fan motor draws 5 amps. My questions are:
  • So what power do I need for the solar panel? Is it as simple as 12v*5a=60 watts?
  • Do I need a 'solar controller? or is this design too simple to need a controller?
  • If I add a battery to this circuit, so the fan will run at night, what size battery do I need?
I would appreciate any assistance that you can provide.
 
rbsWELDER said:
So I would like to add a powered vent to my trailer, and I would like to make it solar powered. This should eliminate the need for a thermostat to open & close the vent.

The 12 volt fan motor draws 5 amps. My questions are:
  • So what power do I need for the solar panel? Is it as simple as 12v*5a=60 watts?
  • Do I need a 'solar controller? or is this design too simple to need a controller?
  • If I add a battery to this circuit, so the fan will run at night, what size battery do I need?
I would appreciate any assistance that you can provide.
Click to expand...


You'll need about 100 AHr battery, and 200+ Watts of solar panel, (I'd plan on 300 watts, as wattage rating is always a best case scenario) and a controller.

The fan will use a bit over a kilowatt hour of power in 14 - 16 hours of no/low sun. You'll need that plus about 20% to recharge the battery during the 8 or so hours of good/reasonable sun.

Then you still need the additional solar power to run the fan during the sunny part of the day simultaneously with charging the battery.
 
Thanks Island Girl! Glad that I asked the question, as I would have been way off.

Thanks again!
 
Island Girl said:
You'll need about 100 AHr battery, and 200+ Watts of solar panel, (I'd plan on 300 watts, as wattage rating is always a best case scenario) and a controller.
Click to expand...
Care to explain how you got your numbers? Please!
 
Aren't there solar powered exhaust vents made for trailers?
 
There use to be a company that made them, but they are apparently out of business.
 
Indycars said:
Care to explain how you got your numbers? Please!
Click to expand...


A 5Amp, 12V motor uses 60W of power . . if it runs for 10 hours, that's 600WHr.

It's reasonable to assume that there's little or no sun at least 16 hrs a day, (at least from the solar panel's perspective) leaving 8 hrs with moderate to good sun in average weather.

That's about 960 watt hours the motor needs.

Divide that by 12V and you get 80 amp hours without adding in any cushion . . . . .

So now we have to look at recharging the battery for the nominally 1000 WHr the fan used, plus keep the fan running while doing that, all in the 8 hour or so window of power producing sunlight.

There's different calculation factors used in the solar industry based on location and solar panel alignment, but solar panel ratings are their best case scenario, and archiving no more than half of that during an 8 to 10 hour period is a reasonable working expectation.
 
Thanks !!!
 
T-Test said:
Have you seen how big 2 150w panels are?

I'd personally give up on this one.
Click to expand...


It takes a lot of panel to harvest meaningful amounts of energy, that's why most solar homes have virtually the whole roof, or sun facing side, covered in panels.

Are there vent models with smaller motors, maybe an amp or two?
 
Bruce

1- Thanks!

2- I had that Ultra-Fab unit in the trailer, since I bought the trailer. Only problem it is rated at 3 cfm, so not much help.

3 - The Maxxair that you suggested is design to cover an opening style to keep the rain out when the hinged cover is open.
 
Island Girl said:
A 5Amp, 12V motor uses 60W of power . . if it runs for 10 hours, that's 600WHr.

It's reasonable to assume that there's little or no sun at least 16 hrs a day, (at least from the solar panel's perspective) leaving 8 hrs with moderate to good sun in average weather.

That's about 960 watt hours the motor needs.

Divide that by 12V and you get 80 amp hours without adding in any cushion . . . . .

So now we have to look at recharging the battery for the nominally 1000 WHr the fan used, plus keep the fan running while doing that, all in the 8 hour or so window of power producing sunlight.

There's different calculation factors used in the solar industry based on location and solar panel alignment, but solar panel ratings are their best case scenario, and archiving no more than half of that during an 8 to 10 hour period is a reasonable working expectation.
Click to expand...

Island Girl - I am back on this project and I need some more help, as my electrical acumen is poor, at best.

When you said the motor needs about 960 watt-hours, that was for the non charging time. Correct? If so, I will need another 480 watt hours to run the fan during day light hours. So was the 1,000 watt hours that you noted above a rounding of the 960? If I am still on the right track, I will need to generate ~ 1500 watt hours in 8 hours. Dividing the 1500 watt hours by 12 volts, I will need a 125 amp hour battery. Also, dividing the 1500 by 8 hours, I will need panels totaling 187.5 watts. Am I on the right track, before I factor in the 50% efficiency of the solar panel(s)?

I have seen many solar panel Controllers on Amazon. Are they just a switch to send power to the load (fan) or to charge the battery? Final question, what size controller will I need?

Thanks for all of your help!
 
rbsWELDER said:
Island Girl - I am back on this project and I need some more help, as my electrical acumen is poor, at best.

When you said the motor needs about 960 watt-hours, that was for the non charging time. Correct? If so, I will need another 480 watt hours to run the fan during day light hours. So was the 1,000 watt hours that you noted above a rounding of the 960? If I am still on the right track, I will need to generate ~ 1500 watt hours in 8 hours. Dividing the 1500 watt hours by 12 volts, I will need a 125 amp hour battery. Also, dividing the 1500 by 8 hours, I will need panels totaling 187.5 watts. Am I on the right track, before I factor in the 50% efficiency of the solar panel(s)?

I have seen many solar panel Controllers on Amazon. Are they just a switch to send power to the load (fan) or to charge the battery? Final question, what size controller will I need?

Thanks for all of your help!
Click to expand...


You're on the right track.

Most home solar setups are intended to augment or replace the power supplied by the Utility company. Some additionally are designed to charge a set of backup batteries that use an inverter to supply the household power.

For what you plan, something more like a marine controller that just uses the panels to charge the 12V battery bank should be more cost effective.

You'll need something capable of at least a 25A charge rate to stay ahead of the game.

Batteries charge at ~15V, so 25A charge would be ~375 watts, so about 400W of panels would be a good plan.
 
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