Solar panel to fan via direct DC connection

jcdentonjcdenton Registered Users Posts: 4
I'm attempting to power a greenhouse fan while the sun's out. I have a 30w fan and a 20w solar panel that struggles to run it on low. I was looking at getting a larger panel but only lower powered models have a dc connection. Most panels have an mc4 connection, I don't know how I'd connect that to the dc input on the fan and the cheap controllers that come with them don't seem to have one either.

My second issue is I'd like to rather than buy a 30w or 50w panel, if I could get a 200w - I found one with a dc output and could likely repurpose it to learn more about what I can do with solar. Would using a higher capacity panel in any way damage the fan or not work as it should.

Thanks for the help

Comments

  • littleharbor2littleharbor2 Solar Expert Posts: 1,592 ✭✭✭✭
    edited February 4 #2
    I run two 12 volt automotive radiator fans from one 65 watt 12 volt solar panel. I use them to ventilate my garage, Has been operating now for 6 years without a glitch. When I connected only one fan to the panel it was screaming, (fast). After I connected the second, in parallel  they ran at a reasonable speed and will vary speed with varying  insolation. These are the exact fans pictured I'm using and they are pretty reasonably priced


    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • EstragonEstragon Registered Users Posts: 4,494 ✭✭✭✭✭
    jcdenton said:
    I'm attempting to power a greenhouse fan while the sun's out. I have a 30w fan and a 20w solar panel that struggles to run it on low. I was looking at getting a larger panel but only lower powered models have a dc connection. Most panels have an mc4 connection, I don't know how I'd connect that to the dc input on the fan and the cheap controllers that come with them don't seem to have one either.

    My second issue is I'd like to rather than buy a 30w or 50w panel, if I could get a 200w - I found one with a dc output and could likely repurpose it to learn more about what I can do with solar. Would using a higher capacity panel in any way damage the fan or not work as it should.

    Thanks for the help
    The MC4 connector on the larger panels is a type of DC connection.  You'd connect it either with an extension with a mating MC4 connector on the panel end (preferable, as MC4 is designed for weather), or by cutting the connector off and splicing to the fan/controller wire (may void panel warranty).

    With larger panels, you'll want to check voltage (Vmp and Voc) specs.  Some will be designed for use with MPPT controllers, and may be too high for this application.

    Another option would be to get a second 20w panel if you can, and wire that in parallel with the existing one.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • jcdentonjcdenton Registered Users Posts: 4
    littleharbor2 said:
    I run two 12 volt automotive radiator fans from one 65 watt 12 volt solar panel. I use them to ventilate my garage, Has been operating now for 6 years without a glitch. When I connected only one fan to the panel it was screaming, (fast). After I connected the second, in parallel  they ran at a reasonable speed and will vary speed with varying  insolation. These are the exact fans pictured I'm using and they are pretty reasonably priced


    Thanks for the advice I like this idea, but am a bit new to be able to wire them confidently therefore am only looking at solar panels with a DC 12v output that are plug and play. This is the specific one I was considering https://www.ebay.com.au/itm/200W-Solar-Panel-Kit-12V-battery-Charger-100A-with-Controller-Caravan-Boat-AU/133642095456?var=433091819735 (hope posting links are allowed).

     My fan has a 3 speed controller and am not sure if the 200w panel is over powered if I could reduce the fan speed by keeping it on a low setting, I assume the car fan has only one speed. This is the fan I'm using https://www.snowys.com.au/breezeway-12v-fan
  • jcdentonjcdenton Registered Users Posts: 4
    Estragon said:
    The MC4 connector on the larger panels is a type of DC connection.  You'd connect it either with an extension with a mating MC4 connector on the panel end (preferable, as MC4 is designed for weather), or by cutting the connector off and splicing to the fan/controller wire (may void panel warranty).


    I've been hoping to find an mc4 to dc adapter to try and use this method, but haven't been able to find one. Is there a logical way I should be connecting the fan I have https://www.snowys.com.au/breezeway-12v-fan to a solar panel, I have an unsafe electric extension running through my backyard that I'd love to replace with a solar option.

    Really appreciate you guys taking the time to help. Cheers.
  • VicVic Solar Expert Posts: 3,079 ✭✭✭✭
    As Estragon mentioned,  you could use MC4 Extensions,  like:
    MC4 Parallel Multibranch Adapters | Northern Arizona Wind & Sun (solar-electric.com)

    etc,   Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • jcdentonjcdenton Registered Users Posts: 4
    Ok thanks just confirming - those interfaces are interchangeable with the standard 12v dc ports on household appliances? I didn't realize that sorry, If so I'll buy one.
  • EstragonEstragon Registered Users Posts: 4,494 ✭✭✭✭✭
    You need to be careful with acceptable voltage ranges on DC loads/appliances.  They may assume either a DC power supply (eg. AC/DC brick, like for a laptop) or a battery.  Direct to solar will likely be a wider voltage range, which some loads may not be able to deal with.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • PhotowhitPhotowhit Solar Expert Posts: 5,549 ✭✭✭✭✭
    jcdenton said:
    ...standard 12v dc ports on household appliances?
    Are you referring to auto outlets? Cigarette lighter outlet?

    To my knowledge there is no 12v DC port (plug?) on household appliances. Those are all intended for vehicle use, they don't carry a safety rating to be used inside where they might be unattended. Those plugs and outlets are horrendous in my opinion.

    Image result for cigarette lighter outlet and plug

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
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