Solar fan: switch to batteries at night? possible?

LloydyLloydy Registered Users Posts: 15
Hi, I'm looking to use a small solar fan to help with air movement around a 3 way fridge. My question is can I switch to batteries at night? Based on the solar panel and fan/motor specs (below), what would be the ideal voltage? And how long could I expect a couple of small batteries (ie AA) to last?

I would appreciate some help with this?
Thanks
Lloydy


Unbreakable Solar Panel:
◦ Cell Material: Single or poly-crystal silicon.
◦ Solar Output: 1.7V, 400mA min. Under a full sun.
◦ Dimensions: 12.8cm x 5.9cm x 0.5cm.
◦ Two Color Lead Wire: 50cm in length with male connector.
Fan / Motor Unit:
◦ A one piece structure with mounting bracket.
◦ DC Motor: 0.5-6.0V, 1,300RPM.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Solar fan: switch to batteries at night? possible?

    The missing info is: how much does this DC fan motor draw?
    Without that number, you can't determine how much panel/battery is needed to run it.

    But yes it is entirely possible to have a panel keep a small battery charged to run a fan 24/7. The big question is: is it practical? Again this boils down to how much current the fan will draw. You may find that spec'd solar panel is insufficient.
  • LloydyLloydy Registered Users Posts: 15
    Re: Solar fan: switch to batteries at night? possible?

    Thanks Cariboocoot,

    Unfortunately I don't have that info. I will see if I can get it.

    Does this figure '400mA' (solar panel output), refer to Amps? I am out of my depth here, but if it is, then I assumed the DC motor requirements would be this amount or less?

    Also I realize that this set up is somewhat 'Mickey Mouse', but hey I need to start somewhere.

    Cheers
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Solar fan: switch to batteries at night? possible?

    Yes: "mA" means "milliamps"; thousandths of one Amp. 400 mA = 0.4 Amps.

    Have you got this set-up already? Sounds almost like one of those "cool your car in the hot sun" window units.

    One important point would be: does it move enough air to actually improve the 'frige's cooling?
    Since it's a 3-way 'frige, do you have 12 VDC available or do you just run it on propane?
  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: Solar fan: switch to batteries at night? possible?

    400 mA is 400 one thousands of an Amp (properly Amperes.) More easily understood as 4/10ths of an Amp or .4 Amps. Or estimated as half an amp, 0.5A.

    Coot is right, tho. You need to know what the fan draws in terms of current. And also the voltage at which it operates. Your specs say that the fan operates from .5 V to 6V. A "couple of AA batteries" will be about 3V. Are they rechargeable? Even if they are, they are not the best choice to power "physical" devices. That is, moving air, pumping water, or just generally physically moving stuff. AA's can work very well for a significant length of time if all they have to move is the "nearly" massless electron or create and emit the totally massless photon. That's quantum stuff. Moving molecules of air is Newtonian and easily analyzed.

    I digress.

    Recapitulation... Must define:1) Volume to be exchanged, 2) Required rate of exchange, ....


    Oh, Hell.... I'm not helping here, am I.

    Good luck!

    K
  • LloydyLloydy Registered Users Posts: 15
    Re: Solar fan: switch to batteries at night? possible?

    Not quite as bad as a "cool your car in the hot sun" unit. But probably not far off and no I haven't purchased it yet.

    The fridge is run on 240V for a couple of days before a camping trip, 12v in the car (only while moving as it draws 10amps) and then gas while camping.

    I have read that a 12v computer fan can help while in the car by ensuring there is air movement around the fridge vents and a solar fan (additional to the 12v fan) can help when on gas while camping.

    So I don't think the requirements of the fan would be that great, just enough to get a bit of air moving. Hence the fairly cheap solar fan, $75 (Australian), might be enough to do the job.

    I was hoping to disconnect the solar at night and switch to batteries. I have a lot of 1/4-1/2 used 1.5V AA batteries and I would be happy to use up. I'm just not sure how many to use based on the specs of the motor?

    Happy to think of any alternative set up if anyone has one?

    Thanks again.
    Cheers
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Solar fan: switch to batteries at night? possible?

    Let's try for a 'holistic' approach on this. :D

    Those AA batteries are likely 1000 - 1700 mA/hrs. If they're "half used" they're probably not up to the task of running a fan for any significant length of time.

    So, is this in a tow-behind camper or what? Is there any reason why you wouldn't want some renewable 12 V power for the whole thing? Go camping often? Just using alkalines and tossing them when they're spent isn't a very good idea.

    As for the fan approach in general, it would be a good idea to get a fix on what sort of fan in what placement gives you the best gain. Blowing air across the evaporator coils is likely to be the best help, circulating air inside the 'frige not so much so. One of the things about night is that it's usually cooler, so the 'frige wouldn't need as much 'help' in staying cool anyway (door isn't opened as much either).

    If you're going to use a solar panel/battery combo, then you'd want the panel to supply not only enough power to run the fan during the day but also enough to charge the batteries for nighttime use. This ups the ante, and would require the use of rechargeable batteries.

    Always best to ask the questions before you spend the money! :D
  • LloydyLloydy Registered Users Posts: 15
    Re: Solar fan: switch to batteries at night? possible?

    Thanks Coot and Kamala for your help on this.

    I also would prefer a 'holistic' approach, so perhaps solar during the day and no batteries at all would be the way to go. fan is set up blowing across evaporator coils.

    If I did go for batteries at night I wouldn't be buying them specifically for the purpose. I'm definitely 'greener' than that. I use the batteries in my line of work and so far rechargeables haven't cut it. I do get a collection of half used batteries which I'm not that happy about but would feel better that they were used completely.

    The fridge is not in a camper, just a portable Chescold absorption fridge for normal tent camping. Will be spending two weeks in the one spot so I've gone for the 3 way option. So a 12v setup at this stage is no go. The 3 ways draw way to much power on 12v thus 12v is normally only used in the car while on the go.

    Cheers
  • System2System2 Posts: 6,290 admin
    Re: Solar fan: switch to batteries at night? possible?

    I think your solar panel would be fine for that small fan. I'm a Biomedical Engineer and deal with a lot of used batteries at the hospital. We replace batteries every year on medical equipment whether it's needed or not, because of regulations.

    So if you're a brave one, just go to your local hospital, find the biomed department and ask them if you could take one of their 'used' leadacid batts. Then tell them the specs of batt that you need. You could get a bit larger than necessary just stay with the same voltage.

    All they do is pay some company to take all their used batteries to dispose of or re-cycle. You'd actually be saving them a little money and plus you'd be recycling batteries yourself that are probably just fine. (ask them to check the batts before you take them)

    We normally have around 300 batteries of all different sizes and shapes, voltages and Ah, just waiting to be picked up by our re-cycling guys.
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Solar fan: switch to batteries at night? possible?

    As to the cool your car in the hot sun fan...someone gave me one once, still new in the box. Utterly useless. It would not start the motor turning unless in absolute direct sunlight. Installed in the window according to the instructions, it never did get any direct sunlight, and so never worked.

    As to the OP:

    RV retailers sell fan/PV combos specifically for this purpose.

    http://www.go-rv.com/coast/do/catalog/page?dealerId=2137&pageNum=272

    Another option might be the fan sold for use with the Nature's Head composting toilet.

    http://www.natureshead.net/store/index.php?main_page=product_info&products_id=4&zenid=13d26f23d46802b6f8e97f9e1ce2618d

    According to the description at the Sunsei page:

    http://www.sunsei.com/shedvent?sc=12&category=69

    "Package Contents

    * 1 x Solar Vent
    * 1 x LED light accessory
    * 1 x Set of rechargeable batteries
    * 3 x Colored plastic cowls (Brown, Green, and Opaque)
    * 1 x Set of spacers and bolts
    * Instruction manual"
  • LloydyLloydy Registered Users Posts: 15
    Re: Solar fan: switch to batteries at night? possible?

    Thanks dhw. Your first link is the one I was looking at (solar fridge fan).

    After thinking about and further reading, I've decided I'm going to go for a simple 12v/solar panel/charge controller set up and not use small AA's at all. This way I can charge my ipod, ipod docking station and camera batteries when needed as well as run a 12V (.25A) computer fan as the fridge fan. Thanks Coots, as I know this was suggested by you early on. Any suggestions on minimum size panel?

    Question for Knivesandgear or anyone else? There is someone here in Aust. selling second hand deep cycle batteries that were used in fire panels. They are 2 years old, in good condition and have been on 'float charge'. They pretty cheap (12V 18AH $25AUD) and come in various AH. Could these be good and cheap way to get started?

    Camping trip is not until Dec/Jan, hope I'm not peaking to early!!
    Cheers
  • mike95490mike95490 Solar Expert Posts: 9,363 ✭✭✭✭✭
    Re: Solar fan: switch to batteries at night? possible?
    Lloydy wrote: »

    Question for Knivesandgear or anyone else? There is someone here in Aust. selling second hand deep cycle batteries that were used in fire panels. They are 2 years old, in good condition and have been on 'float charge'. They pretty cheap (12V 18AH $25AUD) and come in various AH. Could these be good and cheap way to get started?

    They were taken out of service, because they are likely near the end of their projected life. Otherwise, they would take them out next year. You will get some use out of them, but soon you will have to dispose of them at a toxic recycle place, and buy new ones. If really cheap, get them and learn on them and not fry the new batteries.
    They are also likely gel cells, not agm.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • LloydyLloydy Registered Users Posts: 15
    Re: Solar fan: switch to batteries at night? possible?

    According to the seller...'Hi they are sealed lead acid,not gell,dont know about agm'. He also states that they are removed every two years because of regulations.

    Could be pretty tired but could be good for a couple of years.

    Say there okay, is 18AH enough? I calculated if I charged ipod and ipod dock and had the computer fan running all day, I would need 11.82 AMP Hours. I'm thinking 20W panel?

    Cheers
  • mike95490mike95490 Solar Expert Posts: 9,363 ✭✭✭✭✭
    Re: Solar fan: switch to batteries at night? possible?

    You need closer to a 50W panel. and then you add a light , and a radio..... You might want a 100W, just to make it worthwhile and have room for expansion

    Pulling 12A out of an 18A battrey is a pretty deep discharge, they won't last long at that depth.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • South AfricaSouth Africa Solar Expert Posts: 295 ✭✭✭
    Re: Solar fan: switch to batteries at night? possible?
    Lloydy wrote: »
    Question for Knivesandgear or anyone else? There is someone here in Aust. selling second hand deep cycle batteries that were used in fire panels. They are 2 years old, in good condition and have been on 'float charge'. They pretty cheap (12V 18AH $25AUD) and come in various AH. Could these be good and cheap way to get started?

    Camping trip is not until Dec/Jan, hope I'm not peaking to early!!
    Cheers

    That is what I did. I also get 2 year old lead acid's for a steal. They are coming out of UPS'es (so most of the time they where on float, that are replaced as a matter of principal by clients.

    In my opinion, with batteries being one of the most expensive parts, it is a good way to start learning about batteries and how to make them last. :-)

    And have the recycled, once you are done with them.
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