Topic: Daytime FARS to 24 hour FARS (Almost)

[Jim]

I have a Daytime FARS on my Davis VP2 and for some time I have been trying to get It to run like the 24 hour one Davis sells. I am getting real close to doing this. This Is what I have done. Connect the two solar panels up in Series(Plus to negative). Run the other Plus and minus wires to 2 AA rechargable batteries also hooked up in series. Now run the wires to the fan motor but ADD a 33 OHM resistor to the plus wire going to the fan. In direct sun the fan started at 10:00 A.M. and we lost sun to the panel at 4:00P.M. The fan kept running till after 1:00 A.M. when I went to sleep.So I figure For an investment of about $5:00 I have a 15 hour FARS. Not bad for an old IRISHMAN

1 Battery holder
2 AA Rechargable batteries
1 33 OHM resistor

[blackjack52]

That's pretty good!
What kind of rechargeables are you using?  With the constant charging/discharging you might be better off using 800-1000mAh NiCd vice NiMh.

[Jim]

The Batteries are 1850 M/AH Nmh. I am using them because thats what Radio shack had at the time.
What would be the advantage to using Ni Cads? and  dont the ones I am using store more energy?
Jim 

[MesquiteWx]

I am not sure if this follows with electronics, but I know in normal electrical wiring it is never good to connect a positive to a negative. You are bringing the current full circle which can possibly over time short out your electronics. Like I said though, I am not sure if this applies to wiring with electronics.

I know it sounds like it makes sense to go positive to negative that way you have a positive and negative open on each end. Have you tried going positive to positive and negative to negative then tie those directly to your battery holder. You might be able to pull a full charge to your batteries. You can test this with a multi-meter to see what the draw is.

[blackjack52]

The Batteries are 1850 M/AH Nmh. I am using them because thats what Radio shack had at the time.
What would be the advantage to using Ni Cads? and  dont the ones I am using store more energy?
Jim 

I'm sorry.  1850 should be good enough but that also depends on what the draw is from the motor. mAh deals with capacity.  So if you find your fan is not working through the entire night, try a higher mAh rating.  NiCd hold up better for this application (constant charge/discharge) and will hold the charge longer than NiMh.

[Jim]

Thanks for the replies I am currently looking for a 2 Volt 750 M/A panel. Any Ideas where I can get one. I heard from an owner of the Davis system that has the 24 hour fan and his panel puts out 1.9 V at 750M/A running through 2 C cells parallel

[MesquiteWx]

Check out Hobby Stores, sometimes they carry stuff like or if you have a Frys or some other big computer, electronics store they might have it. I doubt Rat Shack would have something of that quality. They have them but they are probably small cheap panels. Maybe even calling Davis and see if they sell replacement solar panels.

[prvrt]

You could try this for a panel http://store.altenergystore.com/Solar-Panels/1-to-50-Watt-Solar-Panels/Sunwize-SC3-6V-3-Watt-6-Volt-Durable-SolCharger/p4123/
or this one
 http://cgi.ebay.com/6-VOLT-SOLAR-PANEL-MOULTRIE-FEEDERS_W0QQitemZ230046200721QQihZ013QQcategoryZ52504QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247
and add 2 more batteries in series for 6v. You could also go with a battery like this
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=1154
or any of these
http://www.batteryspace.com/index.asp?PageAction=VIEWCATS&Category=1034
Then reduce the voltage from the batteries to what you need. Finding a 2v panel will not be easy. By combining the two panels you have now in series, you are at 4v which is not far from 6v. I would also suggest this http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=3064 to ensure you are not overcharging the batteries. You are at 15 hours now, but I am assuming you have good sun light during this test. With the larger panel and more battery capacity, you will have a better chance of keeping the FARS running during cloudy/rainy weather. I guess it comes down to what you want to spend. Just my 2 cents.