Solar powered grow lights

I have 3 400 watt solar panels in use at a remote location that I would like help with designing a Solar powered LED veg light for a 4x8 area. For now I'll be using cheap chinese cobs for the design phase, something like these https://www.ebay.com/itm/50W-warm-white-white-Cool-white-High-Power-12V-32V-COB-LED-Chip-Grow-light-/253077886572?_trksid=p2385738.m2548.l4275.

My first questions will be about driving these cobs and finding a driver that will supply a constant current load@ 12 volts. Any suggestions?

solar is dc, youd just have to match your voltage on your cobs to the voltage that the panels put out, possibly no need for drivers.

battery storage is gonna be interesting///?

You need voltage regulators is all, this way it clips any peaks higher than 12v.

I would still need drivers to keep at the least a constant current value. Something like these. https://www.ledsupply.com/led-drivers/mean-well-ldd-l-series-cc-step-down-mode?gclid=EAIaIQobChMItr23hPyT1wIVllqGCh1LnwONEAQYASABEgLzoPD_BwE

vostok said:

battery storage is gonna be interesting///?

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I already have 8 12V deep cycle marine batteries tied into the panels now. But trying to eliminate the inverter to achieve better efficiency than converting 12V to 110V then stepping back down with the led drivers.

boilingoil said:

I would still need drivers to keep at the least a constant current value. Something like these. https://www.ledsupply.com/led-drivers/mean-well-ldd-l-series-cc-step-down-mode?gclid=EAIaIQobChMItr23hPyT1wIVllqGCh1LnwONEAQYASABEgLzoPD_BwE

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Its one or the other. Those would work

best is to design an LED array that operates just below (but close to) the lower of your minimum solar array voltage and minimum battery bank voltage

use a DC-DC power supply to step down the voltage to match your lights

charge controller for the batteries stays on the high side of this and supplies power to the dc-dc converter when solar array voltage is low

the idea is to use as much as possible directly because battery banks are expensive and lose 10% of your power on charge and discharge

if you ran 12/12 that was centered on your solar maximum day you could use about 75% of the power directly and store the other 25% for use in morning and evening

http://www.solartechnology.co.uk/support-centre/calculating-your-solar-requirments
**The power generation rating of a Solar panel is also given in Watts (e.g. our part number STP010, is a 10W solar panel). In Theory, to calculate the energy it can supply to the battery, you multiply Watts (of the solar panel) by the hours exposed to sunshine.

In practice it’s not a great way to calculate the output from a solar panel so we work to a few simple rules.

· We would generally advise that an average UK winters day will only give you 1 hours sunshine

· An average UK summers days will give you 6 hours of sunshine.

So in winter a 10w panel will provide 10w worth of energy back into your battery. (10w x 1 = 10w)

In Summer a 10w panel will provide 60w worth of energy back into your battery. (10w x 6 = 60w)

Using the above calculation takes into consideration any losses in the system from the regulator, cables and battery you may be using.**
So using those as a rough guide your max daily wattage from your 400w x 3 array will be 1200 x 6 = 7200 W/hrs or 7.2 KW/hrs high summer and about 1.2 KW/hrs mid winter before inversion. You would be best off running dc -dc with a buck converter to regulate the voltage. I would use a series wireing on both my panels and my batteries so assuming your panels are rated at 12v nominal and push around 20v off load then you can series them to for a 36v on load supply and feed them into sets of 3 batteries then use 36-40v cobs. If you adequately cool your cobs then nothing more than a buck converter to ensure stable output voltage with minimal loss would be needed to regulate voltage and over current will be controlled by your thermal regulation of your cobs (big arsed heatsinks) cobs only need current regulation if there is excess voltage or they overheat.
In conclusion; take your minimum solar output, divide by 24hrs then allow 20-30% for storage losses, this will give you your maximum cob array size 1200/24 = 50 x 0.8 = 40 watts
If you invert this then feed drivers with it you will need to lower that number by a further 10-20% for inversion conversion losses. Sorry but it looks like you will need more than 3 x 400w solar panels.

freemanjack said:

In conclusion; take your minimum solar output, divide by 24hrs then allow 20-30% for storage losses, this will give you your maximum cob array size 1200/24 = 50 x 0.8 = 40 watts
If you invert this then feed drivers with it you will need to lower that number by a further 10-20% for inversion conversion losses. Sorry but it looks like you will need more than 3 x 400w solar panels.

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That is part of the reason on running 10 watt 12 volt chips, Less cost of cooling ( can be cooled with just the aluminum c channel mounting), No matter what we use we lose efficiency anytime we convert energy so I'm trying to eliminate or minimize power losses.
My solar availability is averaged at 4.2 hours. So 4.2x1200 watts so that's roughly 5,000 watts. So by my calculations around 300 watts would be max Lighting I could run using those panels. Correct?

boilingoil said:

That is part of the reason on running 10 watt 12 volt chips, Less cost of cooling ( can be cooled with just the aluminum c channel mounting), No matter what we use we lose efficiency anytime we convert energy so I'm trying to eliminate or minimize power losses.
My solar availability is averaged at 4.2 hours. So 4.2x1200 watts so that's roughly 5,000 watts. So by my calculations around 300 watts would be max Lighting I could run using those panels. Correct?

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If you are planning 24hr veging then @ 4.2hrs you could run around 200w but unless you have mains/generator backup, you need to look at your solar minimum rather than average, you will not be able to store summer excess for winter deficit so your maximum array size needs setting to your minimum available energy.

What about cloudy and rainy days. You have to calculate for that as well.

freemanjack said:

If you are planning 24hr veging then @ 4.2hrs you could run around 200w but unless you have mains/generator backup, you need to look at your solar minimum rather than average, you will not be able to store summer excess for winter deficit so your maximum array size needs setting to your minimum available energy.

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16 hours in the veg cycle for these, at least that's what I did for the calculation for 300 watts of lighting.

boilingoil said:

I have 3 400 watt solar panels in use at a remote location that I would like help with designing a Solar powered LED veg light for a 4x8 area. For now I'll be using cheap chinese cobs for the design phase, something like these https://www.ebay.com/itm/50W-warm-white-white-Cool-white-High-Power-12V-32V-COB-LED-Chip-Grow-light-/253077886572?_trksid=p2385738.m2548.l4275.

My first questions will be about driving these cobs and finding a driver that will supply a constant current load@ 12 volts. Any suggestions?

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Use the solar to charge batteries. Led are dc. You don't need a driver per say.

Look into meanwell dc to dc step up or step down drivers.

Solar panel to batteries. Batteries to dc to dc driver. Driver to leds.

boilingoil said:

16 hours in the veg cycle for these, at least that's what I did for the calculation for 300 watts of lighting.

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Ok gotcha, but this still ignores the fundamental problem of winter/low sun times, are you very near the equator or do you have any backup source of power? mains, generator etc, if not you will have to go with your solar minimum not the average. Even a large battery array will only supplement daily solar lows don't expect much more than a day or so reserves. I've lived entirely off grid for a decade in the past so i got a fair bit of experience with this stuff.