# Home solar system - COB LED Drive

Recently, I have installed an off-grid solar system - MPPT charge controller, batteries and solar panels.

Overall the system provides a DC 12/24/36/48v power (60A Max).

The main load I want to drive is a full spectrum COB LED which is used for indoor grow of cucumbers and strawberries.

I have 2 of these LEDs, each is 150W - 300W total - rated at 30V.

Currently I drive them with a standard 220v LED driver power supply.

I was wondering what is the best way to drive these LEDs with the use of solar power -

1. 12/24v to 220v and use the driver I used?
2. Using one the DC Output available with some method of limiting the current?

Or maybe you guys got another solution?

• Are the LED "pure led" or does it contains some driver / resistor in them ? Sep 7, 2018 at 8:52
• A 150W CoB LED requires expensive thermal management. Bridelux and Samsung strips are much more efficient and do not require a heatsink. Sep 7, 2018 at 17:52

## 2 Answers

Assuming there are pure LED, or perhaps just led with a resistance, you can use a current controlled step down buck converter. It will give you more efficiency than going through the 220V, in theory.

Product example

Principle

• Pure LED, the product example current is not high enough isn't it? also, didn't find one with a higher output current rating. Sep 7, 2018 at 10:31
• @SaharCohen The LDD is an excellent driver for horticulture. Your CoB LEDs are the problem. If you use more than 1200 mA you are going to be generating too much heat. CoBs are no longer the best choice for growing plants. Strips are the new way to go. By far. If you were to use CoBs then more and lower powered, would be the way to go. Sep 7, 2018 at 18:23

I did something very similar. I concluded I will never be able to make back the cost of the batteries. I pay 10¢ a kW. For me solar power would only economically feasible if the project is funded with government or utility incentives.

When calculating pay back, do not to forget to include the cost of the batteries.

This is my setup:

Using an inverter to convert 12/24V to 220 VAC then back to a constant current is very inefficient.

You should use the solar DC to power the LEDs.
Use a Mean Well LDD LED driver.

2 of these LEDs, each is 150W - 300W total - rated at 30V.

150 W @ 30V equates to 5 Amp. That does not sound correct.

When growing with LEDs the color temperature and efficacy of the LEDs is very important in the selection process.

This is an experiment growing tomatoes with a cool and warm strip of LEDs.

while you can use lumens/watt to select a line of LEDs with high efficacy you should select the warmer color temperature and CRI. 2700K 90 CRI is arguably the best growing spectrum.

Even though a with in a line of LEDs the higher color temperature (e.g. 5700K) will have a higher lm/W. Plants do not care about lumens only photon quanta. The light source of all common white LEDs is a deep blue (450 nm) LED with phosphor wavelength converters.

Ideally you would like an LED that provides sufficient deep red (660 nm). All white LEDs emit sufficient blue wavelength light and the cool white too much blue for most plant species.

Where a 5700K LED may have an efficacy of 180 lm/W a 2700K in the same series may only have 150 lm/W. But the quantum measurement of photons (i.e. µMol/sec) between the two colors is very similar (e.g. 63 vs 60 µmol/s/m²). The warm will emit slightly less µMol/s, but warm will provide a richer photosynthetic spectrum (quantum photosynthetic yield) than a cool LED.

In your case the optimal voltage would be 24V and to use a 20V LED.

I would highly recommend using 19V Brideglux EB Series Gen 2 strips. Or Samsung F-Series Gen3.

I also recommend starting the seedling with a single 280 mm strip and add strips as the plant grows. It is best to have the capability to adjust the current. This way you adjust the height of the fixture over the canopy then adjust the current for the ideal irradiance.

When the plant gets higher consider using side lighting more than top. The irradiance fades fast with distance according to the Inverse Square Law. As the plant gets taller less irradiance will get to the lower branches. But the distance from the sides to the center stem will lose much less irradiance.

which is used for indoor grow of cucumbers and strawberries.

Did you mean cannabis?

• Of course, switching to two strips, one red and one blue, might produce even better results. Sep 7, 2018 at 18:46
• @Jules that is possible true. 450nm blue and 660 nm red LEDs cost from $1 to$2 each. A 2,500 lumen strip costs \$4. I find the spectrum of the Lumiled Fresh Focus Marbled and Red Meat have a near perfect spectrum. I build my own strips with these LEDs, lumileds.com/uploads/691/DS196-pdf ---- I also have supplemental strips using OSRAM Oslon SSL 150 blue and red. Sep 7, 2018 at 18:55