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