Can I wire 9v 800ma fan into 12v

KO2023 · July 2023

I'm trying to figure out if I can safely add a 02 Cool dc fan into my solar panel system. Will it burn up the fan? Do I need to add something else?
For reference:
Harbor Freight 100W solar panel kit.
I have 4 computer fans 0.7A with 8.4W total load in parallel wired to the controller load output.
I want to cut the AC adapter and use the cable/connector. The specs on the fan is 9v and 800ma.

KO2023 · July 2023

Is my question too simple or did I not add enough info?
Edit to add I forgot to add 12 agm 35ah battery in the system.

BB. · July 2023

Generally, solar panels output (for "12 volt panels" around 17 to 22 volts. Well over 9 volt fan specs.

I would suggest you look at 24 VDC fans... They will run a bit slower at 17.5 volts (typical middle of the day nominal voltage), but they will not be over voltage by the array.

There are other ways of of regulating the voltage to the fans (series diodes, DC to DC converters, etc.)... All the regulation types have a few issues that you need to look at.

The big issue is that solar panels do not really act like a battery--I.e., they do not output 12.0 volts. They output zero volts with no sun, output around 17.5 volts under full (rated) load at noon-time sun (Vmp). And upwards of 21-22 volts under full sun with light or no loads (Voc).

DC to DC converters can be pretty neat... They are pretty cheap and take a wide range of input voltages can can give a regulated output voltage (set for 9 volts if enough sun/not too much load).

For example, here are 6x 3 amp DC to DC converters (buck type for "dropping" input to output voltage). They are cheap and may power your fans (up to 3 fans per converter?)....

https://www.amazon.com/Converter-QEBIDUM-Adjustable-Stabilizer-Efficiency/dp/B099X2ZJFB

There can be an issue with "startup" with converters... The solar panel will supply upwards of 17.5+VDC even in early morning or late evening (weak direct sunlight)....

However, they panels deliver very little current (current is proportional to amount of sun hitting the panel). Converters can get "stuck" in startup with too much load and too little current from panels in low sunlight.

But these type of DC to DC converters are pretty cheap so may be worth trying.

-Bill

BB. · July 2023

Note there are 3 major types of DC to DC converters:

Buck type... Drops input voltage to output voltage (i.e., 24 volts in, 12 volts output).
Boost type... Increase input voltage (12 volts in, 24 VDC output).
Buck Boost... Can take "any input voltage" and output stable output voltage (i.e., 5-48 VDC in, 12 VDC output).

Some are fixed output voltage, others have adjustable output and other interesting features.

-Bill

Photowhit · July 2023

The load output of the controller should be around 14.4 volts on the cheap thunderbolt' controller with Harbor freight kits. Originally the O2cool fans ran at 12volts and might be viable but you could look for a car plug in fan that should handle that voltage.

FWiW - if adapting to wiring into the load controller, you could buy a car plug extension and create an output plug adapter to plug in a car fan.

littleharbor2 · July 2023

I have automotive fans mounted in my garage ceiling to push hot air out of the garage. These fans are hardwired to a solar panel. They have been running for years, every day without a glitch. That being said these fans are built more robust than an O2 Cool fan.

Note; the O2 Cool fan doesn't move a whole lot of air compared to an automotive fan. Plus automotive fans are pretty cheap on Amazon or eBay.. If air volume is important you might think about trying one. They come in many sizes too.

NANOcontrol · July 2023

I was running a 6V outdoor fan for my wife with half a 100W panel (tap in junction box) and a resistor in series. It is a Coleman fan designed to work on 4 D cells. Was looking for a quick solution. Half a panel might work for you. This year I mounted a buck converter in the base of the fan and used full panel voltage. She likes that a lot better. Now when a cloud passes over the speed never changes. There are buck converters for $4 that can be adjusted to 12V and that pump will run a lot longer thru the day.

KO2023 · July 2023

BB. said:

Note there are 3 major types of DC to DC converters:

Buck type... Drops input voltage to output voltage (i.e., 24 volts in, 12 volts output).
Boost type... Increase input voltage (12 volts in, 24 VDC output).
Buck Boost... Can take "any input voltage" and output stable output voltage (i.e., 5-48 VDC in, 12 VDC output).

Some are fixed output voltage, others have adjustable output and other interesting features.

-Bill

I forgot to mention there is a battery. 12v 35ah AGM.
Can I add a buck into the same circuit as the other 4 fans? 16 AWG wiring. Would I add a buck after the 4 and then add the fan or fans? Or would a separate line be safer? I did read something about not mixing voltages on same line. But I've read so much my mind is mush now. Lol

This is on a large chicken coop. I'm trying to add circulation to multiple areas for this extreme heat. As a chicken coop is highly flammable I'm trying to do the safest thing.

KO2023 · July 2023

littleharbor2 said:

I have automotive fans mounted in my garage ceiling to push hot air out of the garage. These fans are hardwired to a solar panel. They have been running for years, every day without a glitch. That being said these fans are built more robust than an O2 Cool fan.

Note; the O2 Cool fan doesn't move a whole lot of air compared to an automotive fan. Plus automotive fans are pretty cheap on Amazon or eBay.. If air volume is important you might think about trying one. They come in many sizes too.

Do you mean the automotive ones you use inside or the engine cooling type?
I tried an inside one with the cigarette adapter as the controller has an input for that, but it didn't blow very hard.

littleharbor2 · July 2023

KO2023 said:

littleharbor2 said:

I have automotive fans mounted in my garage ceiling to push hot air out of the garage. These fans are hardwired to a solar panel. They have been running for years, every day without a glitch. That being said these fans are built more robust than an O2 Cool fan.

Note; the O2 Cool fan doesn't move a whole lot of air compared to an automotive fan. Plus automotive fans are pretty cheap on Amazon or eBay.. If air volume is important you might think about trying one. They come in many sizes too.

Do you mean the automotive ones you use inside or the engine cooling type?
I tried an inside one with the cigarette adapter as the controller has an input for that, but it didn't blow very hard.

I have two of these hardwired in parallel to a 60 watt panel. When I wired a single fan to that same panel it was running ridiculously fast. They work great. they move a lot of air. I started out with 8 inch fans and after about 6 years one finally gave up and I replaced it with a 12 inch model. Look on eBay or Amazon. Pricing is all over the place but I paid about 25 bucks each when I bought mine.

Image: https://us.v-cdn.net/6024911/uploads/editor/sc/5h9y4gl9zrtx.jpg

BB. · July 2023

Problem is that "mechanical" items (fans, pumps, etc.) can take a fair amount of energy (Amp*Hours, Watt*Hours) per day--Which can end up being kind of expensive to power with solar (price of batteries, plus replacements every hand full of years, solar panels, etc.).

Doing things like using the most efficient loads, smallest loads you can use, timer/thermostat to only run the fans during sunny/hot weather, etc. can help.

Really need to estimate/measure the energy needed--And run the math to design a system to support those loads (or run a circuit from your home to the coop and power via 120 VAC instead).

For example... A typical off grid system may use 1/4 of the stored energy in the battery bank (over night, during poor sun weather). For your battery:

35 AH * 12 volts * 1/4 usage per day = 105 WH per day
Fan load: 9 volts * 0.9 amps * 24 hours per day = 172.8 WH per day
172.8 WH per day * 1/0.52 off grid solar system eff (rough guess) * 1/3 hours per day (reasonable minimum sunny day) = 111 Watt solar panel(s) minimum needed per 24 hour per day fan in reasonably sunny location.

So just one fan running 24 hours per day uses a fair amount of battery energy.... Deeper cycling wears the battery out faster, more difficult to recharge during the day (Lead Acid batteries need a lot of sun, and hours of sun per day to fully recharge).

You can add timers/thermostats to only use the fan(s) during day/hot weather to reduce energy usage... But that is additional costs and complexity.

If you only need fans during sunny weather, using fans powered directly from solar panels gets rid of battery(ies), timers, low voltage cutoff (save battery life), etc.

Alternatively, installing low vents (inlets) and a roof top cupola or similar roof venting (outlets) with shutters (if needed for cold weather) is also an alternative (venting can get rid of more heat than a typical smaller set of fans).

Numbers are just examples of how the math works... Can go into more details if helpful.

-Bill

KO2023 · July 2023

littleharbor2 said:

KO2023 said:

littleharbor2 said:

I have automotive fans mounted in my garage ceiling to push hot air out of the garage. These fans are hardwired to a solar panel. They have been running for years, every day without a glitch. That being said these fans are built more robust than an O2 Cool fan.

Note; the O2 Cool fan doesn't move a whole lot of air compared to an automotive fan. Plus automotive fans are pretty cheap on Amazon or eBay.. If air volume is important you might think about trying one. They come in many sizes too.

Do you mean the automotive ones you use inside or the engine cooling type?
I tried an inside one with the cigarette adapter as the controller has an input for that, but it didn't blow very hard.

I have two of these hardwired in parallel to a 60 watt panel. When I wired a single fan to that same panel it was running ridiculously fast. They work great. they move a lot of air. I started out with 8 inch fans and after about 6 years one finally gave up and I replaced it with a 12 inch model. Look on eBay or Amazon. Pricing is all over the place but I paid about 25 bucks each when I bought mine.

Thanks! I've been having a hard time fine the right fan.

KO2023 · July 2023

BB. said:

Problem is that "mechanical" items (fans, pumps, etc.) can take a fair amount of energy (Amp*Hours, Watt*Hours) per day--Which can end up being kind of expensive to power with solar (price of batteries, plus replacements every hand full of years, solar panels, etc.).

Doing things like using the most efficient loads, smallest loads you can use, timer/thermostat to only run the fans during sunny/hot weather, etc. can help.

Really need to estimate/measure the energy needed--And run the math to design a system to support those loads (or run a circuit from your home to the coop and power via 120 VAC instead).

For example... A typical off grid system may use 1/4 of the stored energy in the battery bank (over night, during poor sun weather). For your battery:
35 AH * 12 volts * 1/4 usage per day = 105 WH per day
Fan load: 9 volts * 0.9 amps * 24 hours per day = 172.8 WH per day
172.8 WH per day * 1/0.52 off grid solar system eff (rough guess) * 1/3 hours per day (reasonable minimum sunny day) = 111 Watt solar panel(s) minimum needed per 24 hour per day fan in reasonably sunny location.
So just one fan running 24 hours per day uses a fair amount of battery energy.... Deeper cycling wears the battery out faster, more difficult to recharge during the day (Lead Acid batteries need a lot of sun, and hours of sun per day to fully recharge).

You can add timers/thermostats to only use the fan(s) during day/hot weather to reduce energy usage... But that is additional costs and complexity.

If you only need fans during sunny weather, using fans powered directly from solar panels gets rid of battery(ies), timers, low voltage cutoff (save battery life), etc.

Alternatively, installing low vents (inlets) and a roof top cupola or similar roof venting (outlets) with shutters (if needed for cold weather) is also an alternative (venting can get rid of more heat than a typical smaller set of fans).

Numbers are just examples of how the math works... Can go into more details if helpful.

-Bill

Thanks Bill. You've given me something to think about. I forgot to calculate WH when figuring everything. I figured watts, but didn't factor in WH.
Just one 02 Cool would be 86.4 for 12 hours which would be maximum run time as temps cool at night. Even the 5 cooling fans would be 100 WH for 12 hours.
The fans I bought were the ones from a solar panel kit which have minimal air flow. The coop and run are in a shaded area which is why I picked stand alone panels as they can be away from the coop in a sunny area. Plus dipping my hand into solar without a lot of cost. I do have vents and open areas in the runs, but being in Florida combined with the woods doesn't give much air flow. This humidity is horrible giving us a feels like of 110F or so.
I have been running the O2 fans on AC which do have good air flow. Another reason for solar is Florida hurricane season. Even a hurricane in the area without a near hit can be loss of power for a couple of weeks.
Possibly my best bet is to stay with the AC for the 02 fans and let the little fans work on smaller areas. Addition roof vents would help, also.
I see what you mean for the extra cost. I'd need extra batteries and panels at minimum.
Thanks so much for taking the time to explain everything.

Can I wire 9v 800ma fan into 12v

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