Did I buy a faulty maximiser for my solar-water pump?

Thread Starter

Leahkim

Joined Sep 28, 2017
2
Hey guys,

I am building a solar powered water pump system using a 40 watt solar panel (rated 12V) and a 12V 3A diaphragm water pump.
During high levels of sunlight, my solar panels had an output of 17 volts but as the sun goes down, the voltage drops (if I'm not mistaken) and so the water pump slows down.

I didn't want my pump to be operating below 12 volts so after some research, I bought as 12V mini-maximiser and tested in my school lab.

I had the maximiser connected to a current limiter power supply and a 40 watt load but when I turned the voltage below 12 volts... it had no voltage output. It only turned on when the supply was between 12 and 17 volts. And when it was on, it just gave me the same voltage as the supply.

I didn't test it with the actual solar panel and water pump yet because it has been raining all week where I am but have I 'misunderstood' what the maximiser does?! Or is it faulty? Should I refund it?

Below is the maximiser I bought... please help.
https://www.ledsales.com.au/index.p...ucts_id=1981&zenid=1e58j1uc280ag11adfdto3v7h0

Thank you guys.
 

crutschow

Joined Mar 14, 2008
25,641
You said
I didn't want my pump to be operating below 12 volts
and then you stated
when I turned the voltage below 12 volts... it had no voltage output. It only turned on when the supply was between 12 and 17 volts.
which sounds exactly like what you wanted.
So I don't understand your problem. :confused:

The maximiser circuit is designed to help start a motor from a current limited solar panel.
It charges a capacitor with the load off until it reaches an upper voltage limit and then discharges the capacitor into the load to give a large starting current pulse to the motor and get it moving.
When the voltage drops below 12V (since the starting current is higher than the panel can deliver) it shuts off the current to the motor until the capacitor voltage builds back up, at which point it turns the motor back on.
This on/off cycle rapidly repeats (about 1kHz or so) until the motor is up to speed and the panel current is sufficient to power the motor without help, at which point the circuit ceases cycling.
 

Thread Starter

Leahkim

Joined Sep 28, 2017
2
You said
and then you stated
which sounds exactly like what you wanted.
So I don't understand your problem. :confused:
Hi, Crutschow

Thanks for the reply.

Sorry I made a mistake in my original post. I wanted the pump to still be running at optimal speed when its receiving less than its rated voltage (12 volts).

Just to clarify, are you saying that the maximiser will automatically turn on and off the motor repeatedly until there is sufficient sunlight?

When it was just the motor and solar panel.. the motor still ran in low light except very slowly. My aim for this maximiser was to have it run like it if there is a lot of sunlight during low sunlight conditions (sorry hope that wasn't too confusing).

Thanks again.
 

debe

Joined Sep 21, 2010
1,200
A solar maximiser is doing what its supposed to do.Its also designed to keep a pump running when theres intermittent small clouds going across the panel. When the sun starts to go down theres not enough current to keep the motor going. you don't get some thing for nothing in that situation. Also a 40W solar panel is probably barely up to the job.
 

AlbertHall

Joined Jun 4, 2014
10,542
A current limited power supply has a very different output characteristic than a solar panel so the maximiser will not behave the same as it would on a solar panel. Try the maximiser with the solar panel and see what happens.
 

crutschow

Joined Mar 14, 2008
25,641
I wanted the pump to still be running at optimal speed when its receiving less than its rated voltage (12 volts).

Just to clarify, are you saying that the maximiser will automatically turn on and off the motor repeatedly until there is sufficient sunlight?
No.
Below 12V it will keep the motor off.
Above a certain voltage it rapidly turns the motor on and off during startup.
When it was just the motor and solar panel.. the motor still ran in low light except very slowly. My aim for this maximiser was to have it run like it if there is a lot of sunlight during low sunlight conditions
As debe noted, you can't get something for nothing.
If the panel is not putting out sufficient running current, there is no circuit that can generate more power than you put into it.

The maximiser is to provide addition starting current for the motor when the starting current is more than the panel can deliver.
But it doesn't increase the power.
It does nothing else.
 
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