Solar Vent solution?

The trailer “tinkering” season has just opened and I am seeking inputs from the RAS team regarding a solar vent installation.

I found that the top of the line “Nicro” solar vent delivers about 1000 Cubic feet per hour and runs on a small D looking rechargeable battery for night operation. Given the size of the battery, I doubt that it would run a few days in case of a cloud spell.

I have a trailer that will be soon equipped with two 30W solar panels (60W total). Primary goal is to recharge the glider battery. However, given the size of my panels on the roof, I believe that I could also maintain an extra SLA battery charged in the trailer with a fan running at all times. I found a few brushless fans (mostly designed for computers) that deliver 3000 CFH with a current draw of only 110ma. Doing a quick math, even with 20% of the solar panel capacity charging a trailer 15Ah battery, this system would still run for several days with a high flow rate in case of a cloudy week.. Can anyone envision a problem with this approach? I am looking for lessons learned. The solar panels are already a sunk cost, and I have an extra deep cycle 15Ah battery available. Thus, it looks that I could get a vent with three times the air flow and several more days of autonomy for a faction of the cost of a Nicro fan. Do I miss something?

Thanks – Bastoune

If you upgrade the trailer battery to a deep cycle RV or marine style battery, you'll have enough battery capacity to use a DC to DC battery charger (most hobby shops sell them to the RC crowd) to charge your glider when it's cloudy. Also to run one or two LED floods mounted to the underside of the trailer clam shell for work lights and after dark rigging etc. Trailer battery can jump start cars, run an inverter, and more.

bumper

On 11/29/2013 10:02 PM, Bastoune wrote:

I have a trailer that will be soon equipped with two 30W solar panels (60W total).
Primary goal is to recharge the glider battery.
However, given the size of my panels on the roof,
I believe that I could also maintain an extra SLA battery charged in
the trailer with a fan running at all times.

Thanks – Bastoune

Whatever you do, don't neglect the importance of a good solar
controller. If the controller you select doesn't have one on board, you
will also need an LVD (Low Voltage Disconnect) for the fan. It will
protect your battery from damage by disconnecting the fan if you get too
many cloudy days in a row.

Vaughn

Vaugh,
I found a Solar Charge Controller that can manage two batteries:

http://www.ebay.com/itm/Dual-Duo-Bat...ht_4432wt_1162

Unfortunately, I have not yet found one that can charge two batteries AND manage a load. I have an old charge controller that has a Low Voltage Cuttoff (LVC) and was planning to reuse a portion of that circuit to manage the fan but it is not ideal. Is there such a thing as a Dual battery charger WITH lvc load system? Alternatively, could someone recommend a stand along LVC circuit for a small load?

Bumper - I like your idea of using a bigger battery in the trailer. The ability to recharge overnight would be very good if I were to accidently fly two days in a row. Heck, with a bigger battery, one can also run a small fridge to keep the post-flight beverages cool...

You don't need a battery for the fan. Why would you need to run it at night and suck in all that cool moist night air? Just get a simple 3 terminal regulator set to 12 Volts, use a low forward voltage drop (Shottkey) isolation diode and connect directly to the output of one of your solar cells. The 110 mA computer fan will be running from dawn to dusk, even on cloudy days. I am using a similar computer fan with a 15W panel and it works great.


On Friday, November 29, 2013 10:02:09 PM UTC-5, Bastoune wrote:
The trailer “tinkering” season has just opened and I am seeking inputs from the RAS team regarding a solar vent installation.



I found that the top of the line “Nicro” solar vent delivers about 1000 Cubic feet per hour and runs on a small D looking rechargeable battery for night operation. Given the size of the battery, I doubt that it would run a few days in case of a cloud spell.



I have a trailer that will be soon equipped with two 30W solar panels (60W total). Primary goal is to recharge the glider battery. However, given the size of my panels on the roof, I believe that I could also maintain an extra SLA battery charged in the trailer with a fan running at all times. I found a few brushless fans (mostly designed for computers) that deliver 3000 CFH with a current draw of only 110ma. Doing a quick math, even with 20% of the solar panel capacity charging a trailer 15Ah battery, this system would still run for several days with a high flow rate in case of a cloudy week. Can anyone envision a problem with this approach? I am looking for lessons learned. The solar panels are already a sunk cost, and I have an extra deep cycle 15Ah battery available. Thus, it looks that I could get a vent with three times the air flow and several more days of autonomy for a faction of the cost of a Nicro fan. Do I miss something?



Thanks – Bastoune

Now, my limited understanding going over the years of wisdom contained in the RAS archives (!) is that internal condensation occurs in the evening when the shell of the trailer cools faster than the air inside the trailer. In this case, continuing to run the fan in the early part of the night allows the internal and external temperature to equalize and thus prevent internal condensation. Now, I am not really sure how leaving a fan on all the time works for the better in the morning: The glider has been cold soaked all night and the morning warmer external air is now pulled in the trailer by the fan. Will that warm morning air condensate against the cool glider?

So… fan on or off at night? Fan on until midnight and then off until 10am? A simple timer could help implement a creative schedule for the fan operation if there is a benefit to it.

http://www.ebay.com/itm/LCD-Digital-...em4ac4aa 9de3

Bastoune wrote, On 12/2/2013 6:35 PM:
Now, my limited understanding going over the years of wisdom
contained in the RAS archives (!) is that internal condensation
occurs in the evening when the shell of the trailer cools faster than
the air inside the trailer. In this case, continuing to run the fan
in the early part of the night allows the internal and external
temperature to equalize and thus prevent internal condensation. Now,
I am not really sure how leaving a fan on all the time works for the
better in the morning: The glider has been cold soaked all night and
the morning warmer external air is now pulled in the trailer by the
fan. Will that warm morning air condensate against the cool glider?

So… fan on or off at night? Fan on until midnight and then off until
10am? A simple timer could help implement a creative schedule for the
fan operation if there is a benefit to it.

http://www.ebay.com/itm/LCD-Digital-...em4ac4aa 9de3

The important attribute of air for condensation is the dewpoint
temperature. That doesn't vary much from night to day where I live, so
sucking in the night air won't change that.

Because the trailer top will cool more than the air at night, bringing
in the cool outside air (but still warmer than the trailer top) might
slow the drop in inside temperature, and reduce the amount of condensation.

In the morning, the trailer top might get warmer quicker than the
outside air, but because the warm air rises, it won't help warm the
glider very quickly. So, sucking in cooler air may not increase the
condensation.

Does someone need a college thesis?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)