Topic: Nighttime aspiration mod

[ValentineWeather]

Update because this didn't fix the problem I've removed the nighttime panel and added a second Davis solar panel wired parallel facing SW.

Dead of winter getting less than 7 hrs. of charge time peaking around 450 W/m2 and then you add a couple of cloudy days the 2 C-cell FARS batteries just won't last the night, hopefully, this takes care of it or I'll be going back to the AC fan mode when the ground thaws and I can run conduit. Something I was trying to avoid by going solar

Something I experience often during winter using just 2 C-cell batteries after a couple of days of clouds and snow the solar fan will stop at night causing above normal temps due to lack of airflow being drawn into the 24 hr. shield and across the sht31 sensor.

The solution I've come up with is using a secondary panel that automatically comes on (dusk to dawn) type.
I've only tested this one night so far with great results.  This morning at 7F I could hear the solar fan making that distinctive swirling sound it normally only makes under full sun. 

Do this mod at your own risk: Like I said this has only been tested for 1 night.

It's a simple mod only takes wiring into the existing Davis solar panel. Make sure the polarity is correct or the fan will stop or reverse. Voltage off the panel is 3.7 volts but adjust once wired into around 2.1 volts so it shouldn't fry the solar fan. Voltage should drop to the Davis panel output voltage by default. 
You can test by covering the new panel photocell sensor and forcing the panel on and test voltage, also check polarity once plugged in you will know if the fan spins backward or stops.

These panels I've been using for yard spotlights and have proven dependable going on 3 years in a cold winter climate and no failures on the panel itself.   The name brand has changed but found the same panels under a different manufacturer name I'll link.
 
I think the mythical VP3 should have something like this. Using 2 tiny C-cell batteries just doesn't cut it come wintertime.

https://www.amazon.com/Spotlight-Outdoor-Pathway-Driveways-Automatically-Activates/dp/B07CKRYJRM?ref_=ast_sto_dp&th=1

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[ValentineWeather]

 After 2 days of testing, I can confirm all is well.  The large capacity 4000mah lithium battery solar panels has no problem making it through the long winter night spinning the Davis fan at full designed fan speed.  No longer do you have to put an ear up to the shield to hear the fan when on the C-cell batteries. 
The one downside I see is these fans will wear out faster running at full speed most of the time, the exception is the 1 hour between sunset and when the new panel turns on at dusk and same going back to dawn but IMO it's worth it with the faster response time to change and no worries about dead batteries. 
I run a side by side test with a Barani shield and the Davis is superior in response time to changes, it's just like using an AC fan.

[openvista]

There's a reason why these fans don't need to run at night.... Radiant cooling effectively handles this cooling for you . The Davis units are designed to give you just enough air flow to effectively "cool" the sensors down at night time. To run the fans at full bore at night is just waste......

I think you missed his point. Many of us, including the OP (Randy) at his old house, run AC-powered fans at night. We don't like walking outside and finding that the fan is dead... again.

After you've tried 3 fans in 4 years or had several batteries go kaput, you start searching for RELIABILITY. At the very least, you want a fan that's rated for outdoor use, not the indoor fan that comes standard. An outdoor fan is tested and rated as such (IP55, for instance, for water tightness). Also, a good fan will come with a Mean Time Between Failure (MTBF) specification (50k hours is good).

[CW2274]

There's a reason why these fans don't need to run at night.... Radiant cooling effectively handles this cooling for you . The Davis units are designed to give you just enough air flow to effectively "cool" the sensors down at night time. To run the fans at full bore at night is just waste......

We don't like walking outside and finding that the fan is dead... again.

Without question. Besides, solar insolation/wind or not, the 24hr shield is a very poor passive performer, by design. Granted, Davis gives the option of powering the fan at night, but I'm of the ilk that if it's good enough for ASOS's to run their fans 24/7 (they're designed to have a constant working fan as well), then that's good enough for me.

[openvista]

Nope. don't think I did....

Hmmmm....

Something I experience often during winter using just 2 C-cell batteries after a couple of days of clouds and snow the solar fan will stop at night causing above normal temps due to lack of airflow being drawn into the 24 hr. shield and across the sht31 sensor.

First sentence of first post (emphasis mine). See the part where the fan STOPS. That's what set him into action. The fan running at full speed is merely a side effect of his solution, and a harmless one at that.

[ValentineWeather]

Yes, the modification objective as stated in the first post was to make sure the fan makes it through those multiple days of little sun and long winter nights.  The reason I mentioned the fan speed was assurance there was plenty of juice available and working as planned. I'm very happy with the results.

[ValentineWeather]

There's a reason why these fans don't need to run at night.... Radiant cooling effectively handles this cooling for you . The Davis units are designed to give you just enough air flow to effectively "cool" the sensors down at night time. To run the fans at full bore at night is just waste......

We don't like walking outside and finding that the fan is dead... again.

Without question. Besides, solar insolation/wind or not, the 24hr shield is a very poor passive performer, by design. Granted, Davis gives the option of powering the fan at night, but I'm of the ilk that if it's good enough for ASOS's to run their fans 24/7 (they're designed to have a constant working fan as well), then that's good enough for me.

There is a good reason they don't slow the nighttime aspiration down. One of two mentioned dings on the Davis 24 hr aspiration shield, when tested by WMO was the above normal temperature when the wind was blowing. Even the passive 7714 shield had a better performance with wind. The weak solar fan's inability to overcome the wind causes backpressure raising the temperature slightly inside the sensor chamber is what I see.  Ideally, the AC fan mod does work the best. 

Both JerryG and I have been doing side by side tests with Barani shields against the Davis 24 hr. for some time now. Jerry has reported in another thread a much wider temperature spread with strong wind.  We have another mod both have implemented and not published called the holey shield mod to try and overcome some of these very issues. That mod requires its own thread.  This thread was for improvement on battery life. 

[CW2274]

There's a reason why these fans don't need to run at night.... Radiant cooling effectively handles this cooling for you . The Davis units are designed to give you just enough air flow to effectively "cool" the sensors down at night time. To run the fans at full bore at night is just waste......

We don't like walking outside and finding that the fan is dead... again.

Without question. Besides, solar insolation/wind or not, the 24hr shield is a very poor passive performer, by design. Granted, Davis gives the option of powering the fan at night, but I'm of the ilk that if it's good enough for ASOS's to run their fans 24/7 (they're designed to have a constant working fan as well), then that's good enough for me.

There is a good reason they don't slow the nighttime aspiration down. One of two mentioned dings on the Davis 24 hr aspiration shield, when tested by WMO was the above normal temperature when the wind was blowing. Even the passive 7714 shield had a better performance with wind. The weak solar fan's inability to overcome the wind causes backpressure raising the temperature slightly inside the sensor chamber is what I see.  Ideally, the AC fan mod does work the best. 

I recall that now. I'm glad they see it my way because I run my fan full bore, all 60CFM of it, 24/7. Always have, always will.

[fkapp]

Can you share some details on the holey shield mod?
Understand may be separate thread, so if possible can we start one.
Am interested in how to optimize the shield which many say is one of the best

Thanks
Frank

[ValentineWeather]

Update: Well after several cloudy days in a row fog and snow today the solar fan isn't spinning at 4 am even with the new panel.
So this didn't fix the issue fully.  Fortunately, the shield has the holey mod (holes drilled into welded core) so the sensor still receives airflow. Compared to the Barani shield the temperature is running 3 tenths warm with no sun and light wind.
The holey mod is a backup for times like this giving the inclosed 24 hr. shield a passive aspect.
I'm not recommending drilling holes but test by both Jerrg and me have concluded this mod does work better than no holes when fan isn't spinning and doesn't change the shield performance with fan running. Jerry did it because high humidty at night with fan running destroys sensors. I did it for airflow when fan stops.


 

[ValentineWeather]

Update because this didn't fix the problem I've removed the nighttime panel and added a second Davis solar panel wired parallel facing SW.

Dead of winter getting less than 7 hrs. of charge time peaking around 450 W/m2 and then you add a couple of cloudy days the 2 C-cell FARS batteries just won't last the night, hopefully, this takes care of it or I'll be going back to the AC fan mode when the ground thaws and I can run conduit. Something I was trying to avoid by going solar.

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[ValentineWeather]

Okay here is what I came up with using AC 85-watt halogen floodlamp. 
I can plug into an outlet under the patio and charge batteries using a spare solar panel with extension tieing into the existing panel at the FARS shield. 
Halogen light is similar to the sun so after a few hours, the batteries will be fully charged. JerryG gave me the idea of figuring out a way to either charge batteries or configure an easy swap out method. The charge method was the simplest with the material I have on hand. I just added a couple of quick disconnects on the shield side so it only takes a few seconds to be plugged in and charging batteries.   

[ValentineWeather]

 
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[CW2274]

That's using the ole' noodle, make your own sun. Will this be a daily ritual sunshine or not...or still figuring that out?

[ValentineWeather]

That's using the ole' noodle, make your own sun. Will this be a daily ritual sunshine or not...or still figuring that out?

Oh no, just this time of year thankfully. we have plenty of sunshine the majority of the year.

[ValentineWeather]

I think with a full battery charge I could run at least 2 days with no sun, the problem I run into when I hit that 3rd and 4th day on weak batteries it can't make the 16 hour nights.  Much has to do with temperatures too just how long I can go without sunshine.
The  currently is give a charge every 3rd day if sunshine is limited.  Obviously it will be a learn as I go.

[CW2274]

That's using the ole' noodle, make your own sun. Will this be a daily ritual sunshine or not...or still figuring that out?

Oh no, just this time of year thankfully.

Yeah, kinda figured that would be the case with the days being so much shorter. I was just thinking, I have no idea, but do you think you might try a considerably lesser wattage bulb and see if it'll still do the trick? Phffft, the new bulb would probably cost as much as you would save in electricity. Just a thought..

[ValentineWeather]

That's using the ole' noodle, make your own sun. Will this be a daily ritual sunshine or not...or still figuring that out?

Oh no, just this time of year thankfully.

Yeah, kinda figured that would be the case with the days being so much shorter. I was just thinking, I have no idea, but do you think you might try a considerably lesser wattage bulb and see if it'll still do the trick? Phffft, the new bulb would probably cost as much as you would save in electricity. Just a thought..

Yes, almost any light will work from what I read even LEDs but takes much longer.  The Halogen is closest to actual sunlight and charges the fastest.  Going with what I have on hand, charged for 4 hours today.

[CW2274]

That's using the ole' noodle, make your own sun. Will this be a daily ritual sunshine or not...or still figuring that out?

Oh no, just this time of year thankfully.

Yeah, kinda figured that would be the case with the days being so much shorter. I was just thinking, I have no idea, but do you think you might try a considerably lesser wattage bulb and see if it'll still do the trick? Phffft, the new bulb would probably cost as much as you would save in electricity. Just a thought..

The Halogen is closest to actual sunlight and charges the fastest. 

That's what I meant, a smaller halogen. Nonetheless... "Party on Garth...Party on Wayne"....