Electronics > Power/Renewable Energy/EV's
Solar panel 250 watt to 12vdc without PWM/battery?
DougSpindler:
I was give an LG 255 watt solar panel to “play” with. Output voltage is 30 volts at 8.5 amps. I would like to use it to power a 12 volt waterfall pump during the day. (No need for a storage battery.) I was told I could use a PWM, but when it arrived I found I needed a 12v or 24v battery. (Would like to avoid the need for a battery.)
Here’s my question... What’s the best way to get 12 volts from a solar panel without a battery?
Does someone make a voltage regulator? (I found some 48 volt to 12 volt golf cart regulators, but they were less than half the wattage.)
Could I make my own voltage regulator circuit? (Have’t found one that handles 10 amps.)
Or should I just use the $20 PWM I already purchased and buy a small storage battery?
Thanks
fourtytwo42:
Hi first question before you spend money have you tested the slar panel ? do you know it's good and capable of producing it's full output ?
Second question, you dont say how many watts at 12V your pump consumes.
If your panel has adiquite watts for your pump then a PWM converter will work fine without a battery HOWEVER if the panel is unable to supply the starting power required by the pump you may need some additional energy storage, this does not have to be a battery, it could be a large capacitor for example.
DougSpindler:
Thanks for your reply.
I beleive the panel to be good. Is there a simple test I could perform?
Pump is 1 maybe 2a at 12vdc so 12 or 24 watts or about one tenth of the total ideal output of the panel.
Are you sure a PMW doesnt' need a battery? The one I have is 12 or 24 volt and voltage is autoselected.
fourtytwo42:
Simplest test almost foolproof is short circuit current in strong sunlite and compare with manufacturers spec.
This leaves open the posobility of an open string being bypassed by the anti-shading diode, best way to check for that is test voltage across a 1 amp load (big resistor) and again check against spec.
OK so the pump is tiny reletive to the pane so should work in most light levels.
You dont say what this PWM gadget is you have purchased so I have no idea if it would work but a straight forward 12V regulated output switching converter would do the job although it needs to be designed for your panels Vmpp or have MPPT if you know what all that means :) If your gadget is designed for battery charging it may still work without one.
DougSpindler:
--- Quote from: fourtytwo42 on April 10, 2018, 05:57:41 pm ---Simplest test almost foolproof is short circuit current in strong sunlite and compare with manufacturers spec.
This leaves open the posobility of an open string being bypassed by the anti-shading diode, best way to check for that is test voltage across a 1 amp load (big resistor) and again check against spec.
OK so the pump is tiny reletive to the pane so should work in most light levels.
You dont say what this PWM gadget is you have purchased so I have no idea if it would work but a straight forward 12V regulated output switching converter would do the job although it needs to be designed for your panels Vmpp or have MPPT if you know what all that means :) If your gadget is designed for battery charging it may still work without one.
--- End quote ---
So are you saying in mid-day sun just short the leads of the solar panel together with a 10a ammeter in the circuit.
Link below to the charge controller I purchased. CMG2420 I'm almost certain it won't power on without a battery.
I tried connecting it to an old small 12v sealed lead acid battery (Type found in UPSs) wiht some LCD lights. Worked fine but the battery wasn't able to hold a charge. They I think the charge controller had a diffiuct time with the voltage and somehow confugered itself for 24 volt and burned out the LEDs and one cell in the battery.
I would prefer not to mess with batteries until I know what I'm doing.
Am I correct that the solar panel will produce a voltage/current in some ratio as the the position/iradisence of the sun upto (in ideal conditions) upto 30 volts and 8.5 amps. But say in mid morning the votage might be 15 volts with no load. If say 1 amp load is applied the voltage might drop to 10 volts. (Or something like that?
I appreciate the assistance.
https://www.banggood.com/CMG-2420-12V24V-20A-Solar-Charge-Controller-Panel-Battery-Regulator-Auto-Switch-Overload-Protection-p-1181760.html?utm_source=google&utm_medium=cpc_elc&utm_campaign=ds-diy-mbz-rm1&utm_content=mandy&gclid=CjwKCAjwwbHWBRBWEiwAMIV7Ezl4JMkMSG7kJLwGfsY73u5oRkhMx-aOkkOmtjJDvpFR9TsPFf92wBoCyroQAvD_BwE&cur_warehouse=CN
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