I have 2 COB LEDs (12-14V DC, 50W, I think with 3,75 A in data sheet). I need to run them with a solar panel, it should only run when there is sunlight no batteries needed. Using a 270W panel (open circuit voltage around 38,8V, optimum volt and current: 32V, 8,4A) with 2 parallel connected DC DC Step Down Buck Converters 8-40V 10 or 12A Constant, adjustable current and voltage to run them both separately, it is concerning because the maximum voltage of the solar panel gets really close to the maximum current the Buck Converters can handle.
Using only one LED with a 130 W Solar panel (open circ. volt 22,8V, opt. volt+curr: 17,6V 7,4A) with a 7-32V DC DC step down buck Converter 8-10A also constant adjustable current and voltage. It is concerning that the input voltage may get to low for the converter (because just 38% of the current of the max. output is needed and because the voltages get lower when the temperature gets over the 25°C Standard-conditions.) Which means bad efficiency when there is no perfect sunlight shining.
Or are my concerns unfounded
Please help…
Thank you very much for your answers. I already got the LEDs and the Solarpanel
I got the idea to try it with a buck/boost converter (link) to hopefully solve the voltage problem that comes with a 150W Mono solar cell at higher temperatures (shift down to almost 12V in the worst case (75°C and 0,3-0,4% irridiance)), what do you guys think does it work better that way than with a buck converter?
So in this way: Solar panel -> Buck Boos converter -> LED
I mean the Buck boost converter only costs about 3$ so…
Instead of a Buck converter.
higher voltage, lower amps mean less heat, so there Comes another Advantage with a buck boost converter i guess, because I can go higher with the voltage as I thought (13,5 instead of 12,5V with the buck converter to slightly better handle the temperature-caused voltage Drops) And for the Buck Boost Converter it should be of no or little concern if 13,5 or 12,5V are adjusted because it can both, also a Switch of the converter just stays opened when it gets the same vin as vout is adjusted, am i right? just the current gets witheld in that case)
OK thank you i now ordered a Automatic Buck-boost converter but you are right a mppt Charge Controller (that i have to adjust?or is it enough to connect the battery first with the chargecontroller? ) and a small battery would be better for more continous LED lightning. I found this one https://www.ebay.de/itm/12V-24V-30A-MPPT-Solar-Charge-Controller-Solar-Panel-Battery-Regulator-Dual-USB-/283300643163
… In combination with a small 12V 20AH solarbattery..?
But first i will try it Out without battery so heres my First Plan:
So do you think it works out when i Just wire the 150 W Solarpanel (21,8V opencirc. V) with the Buck-boost converter (How about the polarity of the voltage with buck-boost converters i think i did not fully understood this till now will/can it work too with a combinated step Up/down module instead of a normal Buck converter?) and then to the one cob led that is mounted to an Aluminium heatsink? I also ordered two Buck converters to experiment.
Here are the links to all the articles that i ordered to make it complete:
BUCK BOOST CONVERTER 5-30V
https://www.ebay.de/itm/Automatic-Boost-Buck-Converter-CC-CV-5-30V-To-1-25-30V-8A-12V-24V-Regulator-100W-/132951586178?txnId=1566909161003
BUCK CONVERTER CC CV 7-40V
https://www.ebay.de/itm/DC-DC-Voltage-CC-CV-Buck-Konverter-7-40V-to-0-8-28V-12A-300W-12V-5V-AHS-/302978096967?txnId=1612434223020
BUCK CONVERTER CC CV 7-32V
https://www.ebay.de/itm/DC-DC-CC-CV-Buck-Leistungsmodul-7-32V-Zu-0-8-28V-300W-Konverter-Step-down-DE-K1-/332974029848?txnId=1632235338014
12-14V 3,75A LED:
https://www.ebay.de/itm/10DC12V-50W-COB-LED-Full-spectrum-400-840nm-High-Powe-Grow-Light-for-hydroponics-/263123281373?txnId=2387191590016
Best Answer
Boost or buck converters may not be a good choice for direct-from-sun applications.
They draw more current as the input voltage gets lower. Hence, at the instant when the solar panel does (even for a brief moment) not provide enough power to drive your LEDs at the (maximum!) power you set the converters will quickly spiral the voltage down and your LEDs turn off. Yes, even if the panel only sags to 98% of the LEDs' power demand, the LEDs will turn off.
Also be prepared that a solar panel is much more sensitive to changes in insolation than the human eye. You may find that you hardly notice the difference between 100% and 50% absolute insolation while for the solar panel it already makes 50% of a difference. Don't be disappointed if you only get 10-50% of the rated power out of a solar panel on a seemingly nice sunny day; consider that when dimensioning your system. Maybe do some tests (with smaller panels) and see how much of the rated power you get in weather conditions you consider somewhat average for your location/time of year/day.