BLDC Ceiling Fan running on Solar, Starting Current Issue

Thread Starter

v2birit

Joined Mar 5, 2019
17
Hello,
I have a 12V 24W BLDC Ceiling Fan, that directly works of a 12V 40W Solar Panel. To keep it simple I am not using any Charge Controller & battery. I am ok if the fan stops when a Cloud comes or in the night.
It works fine during the day time. During the evening hours also it works fine with moderate speed. But just in case, you stop it & try to start it during evening time, it does not start & needs to be given a physical push. Once started, it keeps running.
I was looking for a Simple Circuit (may be some capacitor), that could overcome the Starting issue during evening time. Could someone help.
Thanks,
 

MrChips

Joined Oct 2, 2009
21,882
Hello,
I have a 12V 24W BLDC Ceiling Fan, that directly works of a 12V 40W Solar Panel. To keep it simple I am not using any Charge Controller & battery. I am ok if the fan stops when a Cloud comes or in the night.
It works fine during the day time. During the evening hours also it works fine with moderate speed. But just in case, you stop it & try to start it during evening time, it does not start & needs to be given a physical push. Once started, it keeps running.
I was looking for a Simple Circuit (may be some capacitor), that could overcome the Starting issue during evening time. Could someone help.
Thanks,
How do you get any appreciable power from a solar panel in the evening?
 

Alec_t

Joined Sep 17, 2013
11,650
Welcome to AAC!
If you have a capacitor charged to the same voltage as the solar panel generates, the fan motor would not re-start in the evening. A battery kept charged by the panel would be a solution, but would need a charge controller circuit, so not particularly simple.
 

Thread Starter

v2birit

Joined Mar 5, 2019
17
How do you get any appreciable power from a solar panel in the evening?
Well, I live in a tropical area. I have tested this, that the fan runs at moderate speed (even at 12W), so long as the sun is in sight & Solar Panel Turned towards the Sun. Only issue is with the Starting Current. I need to give it a push in the evening to make it Start. Any Idea to make it self Starting ?
 

Bernard

Joined Aug 7, 2008
5,653
I threw this circuit together to solve the low light motor starting problem. It allows a cap. to charge to OC V of panel. C values varied from 5k uF to 22k uF depending on motor.Solar Gleaner # 2 00000.png
 

oz93666

Joined Sep 7, 2010
737
..... To keep it simple I am not using any Charge Controller & battery. I am ok if the fan stops when a Cloud comes or in the night.
I like the way you think .... keep it simple and the electronics to a minimum ...

I think the solution is to up the voltage of the solar input . Is the panel you have 12V open circuit ??? If so buy another panel and put in series ....
My experience with brushless fans and water pumps is that they are very flexible with input voltage ... 12 V computer fans work fine at 20 V with only minimal increased current they draw at 12V ...

If your panel was 24V open circuit the motor would only see around 18V max ... overcast 12V

Adding another 12V 40W panel would of course greatly increase operation time and fan speed , would probably cost no more than building electronic circuitry , and the panels would still be working in 50 years (most circuitry wouldn't).

You can alternatively add in series a 20W 6V panel...all sizes available on eBay.
 
Last edited:

Kjeldgaard

Joined Apr 7, 2016
410
If there are only solar cells and fan connected now, I would start some test with a 10000 or 22000 μF electrolytic capacitor as both help at start-up and low-radiation operation.

The capacitor voltage must be slightly above the open circuit voltage from the solar cells, probably at least 25 volt but preferably 35 volt.
 

Thread Starter

v2birit

Joined Mar 5, 2019
17
I threw this circuit together to solve the low light motor starting problem. It allows a cap. to charge to OC V of panel. C values varied from 5k uF to 22k uF depending on motor.View attachment 171703
Thankyou Bernard So Much. What i can understand from the circuit is that there is a Capacitor and Solar panel in Parallel & this drives the load (motor) through an Electronic switch. This Switch is a kind of Low Voltage Disconnect/Reconnect (LVD). I will try it out. Thanks again.
 

Thread Starter

v2birit

Joined Mar 5, 2019
17
I like the way you think .... keep it simple and the electronics to a minimum ...

I think the solution is to up the voltage of the solar input . Is the panel you have 12V open circuit ??? If so buy another panel and put in series ....
My experience with brushless fans and water pumps is that they are very flexible with input voltage ... 12 V computer fans work fine at 20 V with only minimal increased current they draw at 12V ...

If your panel was 24V open circuit the motor would only see around 18V max ... overcast 12V

Adding another 12V 40W panel would of course greatly increase operation time and fan speed , would probably cost no more than building electronic circuitry , and the panels would still be working in 50 years (most circuitry wouldn't).

You can alternatively add in series a 20W 6V panel...all sizes available on eBay.
Thankyou oz93666. This is also an option. Add more Solar Power. But only catch in this option is that in the peak of afternoon, when Sun in blazing, it can pose a risk to the motor, unless we have some kind of Voltage Regulator.

If there are only solar cells and fan connected now, I would start some test with a 10000 or 22000 μF electrolytic capacitor as both help at start-up and low-radiation operation.

The capacitor voltage must be slightly above the open circuit voltage from the solar cells, probably at least 25 volt but preferably 35 volt.
Thanks Kjeldgaard. True. I need to experiment on the Size of Capacitor to be used. My BLDC Fan takes 2 Amp max at 12 V (i.e. 24W). But also works on less i.e. 1 Amp 12 V (12W).
 

Bernard

Joined Aug 7, 2008
5,653
The P ch. FET, FDS9435A, 5A. SMT. LL, is the only P ch. FET in my bucket of parts, so maybe
some one can suggest a more available one.
A lost member, ronv, posted a similar circuit using a N ch. FET, but not able to retrieve it, but P ch. ckt. could be modified if necessary.
 

Thread Starter

v2birit

Joined Mar 5, 2019
17
The P ch. FET, FDS9435A, 5A. SMT. LL, is the only P ch. FET in my bucket of parts, so maybe
some one can suggest a more available one.
A lost member, ronv, posted a similar circuit using a N ch. FET, but not able to retrieve it, but P ch. ckt. could be modified if necessary.
Ok Thanks. Bernard, one more query. The Capacitor & Solar Panel are disconnected from the load when voltage falls below a Threshold say Vth1.
When are they are reconnected to the load ?. is it when the voltage rises above the same Threshold Vth1 or a different threshold Vth2 ?
 

Bernard

Joined Aug 7, 2008
5,653
Ref. V is 5.6V, feed back blocked by D1. Sun is coming up, V on pin 2 is rising & when it reaches 5.6 V,
SP now at 18V, pin 1 falls to 0 V , motor is connected, - feed back enabled, ref V now about 4 V. Now if SP V
falls below about 12 V the charging cycle starts again but if SP V stays above 12 V , then motor continues to run.
A possible FET, IRF9540, 100 V, 19 A, P ch. TO 220
 

Thread Starter

v2birit

Joined Mar 5, 2019
17
Ref. V is 5.6V, feed back blocked by D1. Sun is coming up, V on pin 2 is rising & when it reaches 5.6 V,
SP now at 18V, pin 1 falls to 0 V , motor is connected, - feed back enabled, ref V now about 4 V. Now if SP V
falls below about 12 V the charging cycle starts again but if SP V stays above 12 V , then motor continues to run.
A possible FET, IRF9540, 100 V, 19 A, P ch. TO 220
Thank. It is Clear now!!! So the Disconnect voltage = 12V & Reconnect Voltage = 18V. Super.
 

MisterBill2

Joined Jan 23, 2018
7,035
It may also work to simply have that large capacitor across the solar panel output all the time. That would be a very simple thing to try. Then, if that was not enough, add a schottky diode in series for charging the cap during the day, and a switch so that you could then start the fan with the charged cap and after it is spinning switch back to running it directly off of the panel.The idea being that during the day the cap could charge up to more than the 12 volts, and so have a bit extra to start the fan. And still you would not have a lot of extra parts if it does not work. So no wasted money or resources.
 

MisterBill2

Joined Jan 23, 2018
7,035
OK, so how about having the solar
A 3000 uF C , 20meg ohm leakage, dropped 1 V in 2 hours. I don't believe a C will be of much help by morning.
What about using the solar cells to charge a battery? I had not realized that the goal was starting the first thing i the morning. AND, what is so very awful about giving a fan a push to start it, unless it is high up and not easily reached by hand. In a house with ten foot ceiling heights it could indeed be a pain, I suppose.
 

Bernard

Joined Aug 7, 2008
5,653
And I could be wrong, C measures 10.6 V this morning.
R 1 could be any value from 10k to 100k, 32k 10 turn was in my bag.
 

oz93666

Joined Sep 7, 2010
737
This whole thread has become ridiculous from lack of accurate data!

Just what is a 12V 40W Solar Panel ???

12V open circuit ??? ........ If so the voltage will be about 9V when load is matched to get maximum power of 40W ... and the fan ,which is not matched for max power , even in strong sunlight will only see about 10V ... I suspect the fan comes to a halt close to 4V ....

TS needs to tell us what it says on the label on the back of the panel . Or measure voltage in max and min sunlight at fan.
 
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