Solar panel

[tarnold]

Just got a 100w panel and want to run a 12v 80w radiator fan, NO BATTERY. The panel is cranking out 23v do I need to put a controller in the middle. All controllers I look at have a battery hookup between the panel and output.

[steveMc]

Hello!
I want to buy myself a portable solar panel Acenew 200 W.
Or is it better to buy a stationary panel?

[CA_Traveler]

Most panels don't have blocking diodes which would be undesirable for series connections. Instead the controller prevents back feeding at night.

Plus without a battery there is no back feeding. :B

[2112]

Gdetrailer wrote:
Oh, yeah, by the way, there are lots of solar powered fan systems like what the OP wants to do which does not use a battery, does not use a charge controller and does not use a timer..

SEE HERE

One sample of many to choose from..



$139 here

Well there you go OP. It was already all packaged up for you. That takes the guesswork out of it.

I wonder if it has a diode on the panel output

[2112]

"Solar panels are already designed WITH a "blocking diode"
They must have somehow fell off on mine. I had to install my own schottky. Manufacturer said so.

"high power/high torque stepper motors (all PWM DC voltage by the way)"
You think there wasn't any EMI protection in those controllers? Check the schematic.

"Not once has there been any "series or parallel inductors" involved at the motors or in the motor drive electronics."
The motor winding IS the inductor

"at a speed faster than you can run"
LOL I haven't ran in over 20 years, unless I need to get to the john

[Gdetrailer]

Oh, yeah, by the way, there are lots of solar powered fan systems like what the OP wants to do which does not use a battery, does not use a charge controller and does not use a timer..

SEE HERE

One sample of many to choose from..



$139 here

" About this item

100% SOLAR FAN SYSTEM - An excellent solution for the exhaust of chicken coops, greenhouses, sheds, pet houses, and windows, the 100W solar panel 12-inch fan kit can push hot air out and push into the cold air, thereby effectively reducing the indoor temperature and keeping the air fresh.
800CFM LARGE AIRFLOW - The DC fan adopts an efficient and easy-to-install design, with a maximum diameter of 12 inches. The powerful airflow can satisfy most chicken houses, greenhouses, small warehouses or attics.
INDOOR INSTALLATION - The exhaust fan needs to be installed indoors and is not suitable for direct sunlight and rain. The solar panel is completely waterproof, and the connection point can be fixed with heat shrinkable tubing.
SAFETY PROTECTION - The 12-inch DC fan is equipped with a plastic protective net, which can effectively prevent small animals from being injured and protect the fan blades from running. Nevertheless, we recommend installing the fan in a higher position.
NOTE BEFORE USE - The speed of the fan is greatly affected by sunlight. When the sun shines directly on the solar panel, the fan can reach 3000 RPM. When the sunlight is weak, the fan will work slowly or even stop working. The solar fan has no built-in battery and can only work during the day.
"

[Gdetrailer]

2112 wrote:
You said "inductance is an AC thing...". Actually you wrote "a AC thing" but I'm not the grammar cop.
I guess I should have been more direct and replied "inductive reactance is an AC thing, inductance affects both AC and DC circuits".

I continued by providing a few examples where "inductance" in a DC circuit can be either beneficial or detrimental. You somehow interpreted this as I implied a LR filter suppresses back-EMF. You might want to re-read my post.

As far as DC motors not having the capability of creating detrimental EMF, some guy named Lenz might disagree. I sure could have saved the company a lot of $ not designing in those flyback diodes.

I could have saved them millions by not including those worthless little inductors on the DC power input pins of all those hot-swap signal conditioning modules. I would have been a hero.

And then, to finish it up, you accuse me of some scare tactic to get OP to spend a buck fifth on a blocking diode? WHAT?

Solar panels are already designed WITH a "blocking diode" which is there to prevent the panels from draining the battery source when the sun doesn't shine.

Adding another diode to the chain isn't going to "protect" the panel and just wastes and robs you of .7V of the panel voltage.

As far as "inductors" goes, have worked with many high power/high torque stepper motors (all PWM DC voltage by the way) used in very large robotics systems (some of these are the size of a average room in a home). Not once has there been any "series or parallel inductors" involved at the motors or in the motor drive electronics.. Those motors propelled 500+ lb gripper assemblies up and down the track up to 20ft in length at a speed faster than you can run. Motors and controllers tend to live very long lives, had more issues with gearboxes and cable failures..

[2112]

You said "inductance is an AC thing...". Actually you wrote "a AC thing" but I'm not the grammar cop.
I guess I should have been more direct and replied "inductive reactance is an AC thing, inductance affects both AC and DC circuits".

I continued by providing a few examples where "inductance" in a DC circuit can be either beneficial or detrimental. You somehow interpreted this as I implied a LR filter suppresses back-EMF. You might want to re-read my post.

As far as DC motors not having the capability of creating detrimental EMF, some guy named Lenz might disagree. I sure could have saved the company a lot of $ not designing in those flyback diodes.

I could have saved them millions by not including those worthless little inductors on the DC power input pins of all those hot-swap signal conditioning modules. I would have been a hero.

And then, to finish it up, you accuse me of some scare tactic to get OP to spend a buck fifth on a blocking diode? WHAT?

[Gdetrailer]

2112 wrote:
"inductance" is an inductor thing. DC motors and solenoids have "inductance" which will create transient EMF with a fluctuating source voltage or current and back-EMF when powered off. Hence the use of a flywheel diode.

DC circuits are not "steady state" 100% of the time. They have to be powered on and off. A low pass LR filter is a common in-rush suppressor on DC capacitive circuits and circuits designed to be hot swapped. It wouldn't work without "inductance".

Regardless, my suggestion of a series diode was to protect from any unknown reaction of powering a large motor

But thanks for the lecture

Brush DC motors even large ones will not have enough "back EMF" to cause issues due to the constant switching actions.

It is no worse than turning a switch on/off/on/off on a DC motor.

LR circuits are typically used in power supplys to filter out any remaining 60hz that may be present from a brute force unregulated powersupply. Has nothing to do with supposed back EMF but all about providing a clean DC powersupply voltage.

Good quality brush DC motors will however have a small value capacitor placed across the input terminals. That capacitor is present to reduce the RFI noise generated by the brushes and switching action of the commutator. Has nothing to due with back EMF but for RFI reduction which can affect radio and TV reception close to the motor.

There are tons of DC motor devices setup and running in this same panel/motor configuration all without any LR, filtering/charge controller or battery. This is often done with pond aeration and ventilation systems which doesn't need to run 24/7.

OP will not destroy the panel running a DC motor directly from it, quit scaring people into spending more on stuff than they need to.

[2112]

"inductance" is an inductor thing. DC motors and solenoids have "inductance" which will create transient EMF with a fluctuating source voltage or current and back-EMF when powered off. Hence the use of a flywheel diode.

DC circuits are not "steady state" 100% of the time. They have to be powered on and off. A low pass LR filter is a common in-rush suppressor on DC capacitive circuits and circuits designed to be hot swapped. It wouldn't work without "inductance".

Regardless, my suggestion of a series diode was to protect from any unknown reaction of powering a large motor

But thanks for the lecture

[Gdetrailer]

2112 wrote:
I vote for hook it up and try it. You won't harm the panel. If it's an automotive radiator fan they are rugged. You may not get to full speed but see what you do get.

The fan is a big inductive load so placing a diode on the positive output of the panel may not be a bad idea. Plus the diode will lower the voltage a bit.

Come back and let us know how it worked out

Automotive radiator fan is a DC motor.

"inductance" is a AC thing and does not come into play with a DC motor.

No need for a diode in this case.

DC motors do come in some variations, brush and non brush.

Brush type uses a set of brushes to get the DC to the rotor.

Brush types are inexpensive but because of the switching action of the brushes against the rotor commutator often creates small arcs at the brushes which can generator RFI but even that should not be enough to damage the solar panel.

Brushless types use a rotor with permanent magnets and outside field coils which are driven electronically by a chopper circuit. Generally more expensive, quieter and more energy efficient than brush types.. But once again, no inductance issue.

With that said, I would agree with just hooking up the fan motor directly to the panel.

Yes, the panel is rated at a higher voltage than the motor, but the panel is not going to be able to develop full rated voltage with the motor load current. In fact what should happen is the heavy current draw of the motor should reduce the voltage of the panel to 12V or lower. The panel will "self limit" the current and it does that due to the panels own internal resistance. This will not harm the panel since the panels full amp rating is developed only when the output leads are shorted together (which is how they test them)..

[Boon_Docker]

valhalla360 wrote:
If the controller does require a battery, you also will need a timer.

If you put a battery in and the fan runs when there is voltage from the battery, the battery will tend to run down at night. Might last a few weeks but constantly running the battery to 0% charge will kill the battery very quickly.

This 12V timer would work for your application.

[Lwiddis]

I agree with Boondock Docker. With the minimal cost difference between PWM and MPPTs why not go with the more efficient MPPT?

[Boon_Docker]

ewarnerusa wrote:
Sounds like a nice controller, but now you'll need a battery. In fact, many controllers will be damaged if you hook solar input to them without having it hooked to a battery.
I'm not sure why someone said it needed to be an MPPT, we're talking a single 100 W 12V panel here. I'm not saying MPPT can't provide more than PWM, but on a small scale like this it is not something worth paying for.
Some controllers do have a "load" output which would do what you're trying with the fan. But I think would still need a battery.

The difference between PWM and MPPT would be at least 1.5 amps more using an MPPT controller with that panel.

[valhalla360]

If the controller does require a battery, you also will need a timer.

If you put a battery in and the fan runs when there is voltage from the battery, the battery will tend to run down at night. Might last a few weeks but constantly running the battery to 0% charge will kill the battery very quickly.