Need to find Grow lights with less than 1 amp input draw.

I have been trying to find a way to run grow lights above my raised garden bed in my hoop house in the winter months using deep cycle batteries and solar panels to recharge them. I could run lights for many hours if I can find lights with less than a 1ah draw, but I can only find lights with more than 3 amp inputs. I have an 8ft long by 3.5ft roughly 28sqft growing area. Is this impossible?

My main issue is I don't have enough solar energy to recharge the system quickly if I use more than 10% of my battery's capacity, roughly 22ah, so I could run 1ah of lighting for 11 hours for 2 days before needing to recharge the battery.

I am also off grid and would love a solution to such a problem, but I do not think it’s feasible. When I was doing so on grid about 5yrs ago, for decent vegetative growth indoor growers look for at least 40w/sq foot. 60-100w is more ideal and necessary for good flower/fruit production. That would put your 28sq ft at 1120w+, which is about 11amps at 120v if my memory and math estimates are correct. I know technology has progressed l, but I doubt to the point of 11x the efficiency. A certain amount of light is a certain amount of energy, and once we light a space in a way to mimic a nuclear reactor millions of times the size of the earth (the sun), we then almost always have to actively ventilate with fans, which usually draw a significant fraction of the power used for light. Of course you don’t need light all the time in a hoop house, but you need it on days we don’t get much solar power. I am considering micro hydro as an alternative, as its not inversely correlated with when power is needed for lighting like solar. Wish I wasn’t such a downer, but this is part of why I do not grow indoors anymore.

The best grow lights I know are happy leaf, and they say they need about 11 watts per square foot of grow space for leafy veg.

So.... You need a lot more solar and battery to do what you want.

So far I found this light which will cover a 2ftx2ft area and uses .84ma per light. To cover my whole bed I would need 4 of them which would give a total of 3.36ah. This is not bad honestly if I had better solar panels or 1 or 2 150w polycrystalline panels this could be feasible. But for now, I only have 80w of panels so 1ah would be max. The problem is the cost of the equipment if I bought everything to do this, I would be looking at $2-$2,500, to grow lettuce in an 8x3' space, this is kind of ridiculous. But if you do the math and calculate how much lettuce you would buy in 2 months, let's say you buy 10 types of leafy greens per week which are approx $2.99 each at the store. It would take 10 years to save back the money invested in an off-grid greenhouse with supplemental lighting in winter. You could run 8 of these lights inside your home @ 12 cents a Kwh, and it would cost you $1.50 a day for 2 months, and over 10 years that is $1600 including the cost of the light fixtures, but you could grow $8650 worth of leafy greens, growing only 2 months a year, which would be about 4 heads of lettuce per day, which most people wouldn't go through, so you are going to possible have a surplus of food. Now, if I ran only 1 light and grew only a 2ft by 2ft patch of leafy greens per month I could grow about 16 plants in my hoop house, which over 10 years would save me about $1080 at the store, this would cover the cost of batteries, 2x 40w solar panels, inverter,  and the light over the 10 years span. Now the only feasible leafy greens I can think of that would grow and be harvestable in 4 weeks would be Arugula, spinach, and beets, and Arugula only needs 4" spacing between plants so growing 16 plants under 1 light is possible.

My thinking is that if you want to grow food in winter, it is best to do it inside, on the grid, and on a larger scale. Outside off the grid on a larger scale, doesn't make $en$e, but if outside off-grid on a small scale, you will break even on your investment.

The set up for a small scale off-grid winter greenhouse lighting system would be:

2x 6v 220ah deep cycle batteries, in series (switching between each every 2 days so one bank can get charged while the other supplies power)
2x 6v 220ah deep cycle batteries, in series ($400 used)

2x 40w mono solar panels ($200 used or on sale) come with a charge controller.

1x pure sine wave power inverter 1000 to 1500 watt continuous $200

1x sf1000 light $200

Total cost $1000 cad

The 2 40w panels could supply a max of 4.44ah of charge to the batteries which would take about 11 hours to recharge 22ah discharged at 11 hours a day over 2 days, so if the panels average 2ah, then charging it would take about 11 hours of sunlight over 2 days to recharge the system.

Why can't I be interested in normal things?


Grow light link

R Scott wrote:The best grow lights I know are happy leaf, and they say they need about 11 watts per square foot of grow space for leafy veg.

So.... You need a lot more solar and battery to do what you want.

The happy leafs still consume 2.16ah and do cover a 4x4' area, but 2 of these would be 4.32ah and would not work. The Spider Farmer SF1000 LED Grow Light consumes .84mah but only covers a 2x2' area, 4 of these would be 3.34ah which would be less than the happy leaf, and the Spider Farmer SF1000 LED Grow Light is a lot cheaper cost.

Ben Zumeta wrote:I am also off grid and would love a solution to such a problem, but I do not think it’s feasible. When I was doing so on grid about 5yrs ago, for decent vegetative growth indoor growers look for at least 40w/sq foot. 60-100w is more ideal and necessary for good flower/fruit production. That would put your 28sq ft at 1120w+, which is about 11amps at 120v if my memory and math estimates are correct. I know technology has progressed l, but I doubt to the point of 11x the efficiency. A certain amount of light is a certain amount of energy, and once we light a space in a way to mimic a nuclear reactor millions of times the size of the earth (the sun), we then almost always have to actively ventilate with fans, which usually draw a significant fraction of the power used for light. Of course you don’t need light all the time in a hoop house, but you need it on days we don’t get much solar power. I am considering micro hydro as an alternative, as its not inversely correlated with when power is needed for lighting like solar. Wish I wasn’t such a downer, but this is part of why I do not grow indoors anymore.

1120w/120v = 9.33A still more than I would want for off-grid. But yes, if I were to follow 40 watts per sq ft. then I could only cover 3 sq ft. while being at exactly 1A.

The other thing that I am reading that is concerning is the ah loss of converting dc to ac voltage, and that for every 10W ac produced 1A dc battery capacity is required. so this would mean for a 100W light, 10Ah per hour will be consumed by the conversion. So instead of getting 1ah per hour consumption for 22 hours of lighting, you would actually consume 220ah of battery capacity. So I really can't figure out how to work out an off-grid light setup unless I used 12vdc lights at a maximum of 12w to meet the 1ah draw from the batteries, I have found 960 lumens 12w 12vdc light bulbs, but I am not sure how sufficient that would be for growing Leafy greens or how much space that would cover.

I found evidence of someone trying to grow lettuce with 2 900 lumens tube lights and they did not have success so perhaps 2 960 lumens 12w 12vdc bulbs running for 5.5 hours a day might work. Between the 5.5 hours of artificial light and the probably similar amount of natural light available in the winter, this may work.

The happy leaf are 12 v, so that saves you the conversion.  But there is just a minimum amount of power density needed, no way around it.  The sun is awesome, we make mediocre substitutes at best.  

Your prices for panels looks way high, I can get 250 watt panels for $50. Get bigger panels and spend extra plus the inverter money on batteries.

Here's an 1800 lumens 12vdc 20w 1.6a 24" long light, which could run for 6.875hrs per day for 2 days. Could maybe supply enough light for lettuce in a 2'x2' area. This might be the winner.

https://www.thecabindepot.ca/collections/12-volt-dc/products/kedron-led-20-watt-24-inch-12vdc-warm-white

R Scott wrote:The happy leaf are 12 v, so that saves you the conversion.  But there is just a minimum amount of power density needed, no way around it.  The sun is awesome, we make mediocre substitutes at best.  

Your prices for panels looks way high, I can get 250 watt panels for $50. Get bigger panels and spend extra plus the inverter money on batteries.

They are 12 volts but still use a 120v adapter, which would still add more current draw, and they are 100watts, even at dc they would still draw 8.3a. Maybe in the US panels are cheaper but in Canada, they aren't even though we make them here, I did find a Canada Solar brand panel 300watts polycrystalline for $250cad, but they are huge compared to what I have.

Have you seen these new fish eye led grow lights?

https://www.opticledgrowlights.ca/collections/veg-lights/products/optic-1-veg-cob-led-grow-light-54w-5000k-cob

Also, have you considered using a light mover?

Scour Kijiji for deals on panels, they can be had, though February isn't a great time to be buying. Complete home systems being uninstalled can provide good deals, or leftovers/rejects from large-scale commercial installs.

Maximizing the amount of light that hits your plants may be worthwhile, so whatever that may mean in terms of a reflective environment.

I'm also on solar-power, and am also looking for ways to run grow lights. It's tricky. Right now heat-lamps for chicks are burning up most of my power... and here comes another cold night.

Do you have a running stream/river close by?

I would love to set up micro-hydro to provide 24/7 power, but the only suitable stream is way at the back of my property, some 600m away.

Ryan Adobe wrote:Have you seen these new fish eye led grow lights?

https://www.opticledgrowlights.ca/collections/veg-lights/products/optic-1-veg-cob-led-grow-light-54w-5000k-cob

Also, have you considered using a light mover?

Hey those are cool but still have the issue where when run through an inverter it will draw 5.4 amps, but when used indoors with a 120v outlet it only draws .5A which is really good, now it would be interesting to see if you could run them straight off of a 36v battery bank because then it would only draw 1.5a since it says the Forward voltage is 36v whatever that means.

Forward Voltage: 36V

Max Current Drive: 3600ma

Actual Power Draw: 54 watts

Amps: .5 amp

COB Max Power: 137 Watts

Finish: Anodized Black

COB Holder: Solderless

IP Rating: IP65 Water Resistant

Fixture Weight: 4.4 Pounds

Shipping Weight: 5 Pounds

Product includes: 120v power cord, 1 Rope Ratchet Hangers & LED Fixture. (120v-240v power cords available, we automatically ship the correct power cord for your country)

J. Rosseau wrote:Do you have a running stream/river close by?

I would love to set up micro-hydro to provide 24/7 power, but the only suitable stream is way at the back of my property, some 600m away.

Nope this is what I am working with https://permies.com/t/138417/Greenhouse-Raised-Bed-Tiny-Backyard#1210196 currently I just don't grow plants Jan and Feb. I was just trying to find ways to grow all year in my polar vortexing butthole of a backyard.

That cabinet light does not have the intensity to grow, it would be fine for sprouting.  

There is an absolute minimum requirement in time and intensity for plants to GROW, to do less and they will only just stay alive.  You are trying to spread yourself too thin.  It doesn't work, been there myself.  I have ten times the grow lights this year as I had last year. I still don't have enough.

I don't remember values for specific plants but I know a lot of Chinese winter greens have lower light requirements compared to commercial western varieties.

As you can see we get plenty of sunlight here in Ontario in February, it's just a matter of trying to use Elliot Coleman's greenhouse science of using multiple layers of plastic cover to increase temperatures inside a cold frame that is inside a greenhouse, while dealing with snow, wind, and darkness. I am sure the added heat from the grow light I put in the cold frame inside the hoop house will be fine for providing a growing climate, it's really just a matter of daylight hours and using stored energy to run lights inside the cold frame to produce light and heat to allow things to grow. I would be interested to see if it can be done with such a low wattage of light as the $28 20w 12vdc one, and be able to recharge with only 80w worth of panels. This could be the only way I could think of to grow food in the coldest months of a typical Canadian winter, for less than $1000, provided you already have a primitive hoop house and cold frame. If I put an insulating blanket over the north side and left and right side of the cold frame, I could still allow sunlight in through the lid at the south side and have the led light bar inside the plastic cover where the plants would be. this way as the sun goes away the solar lights could kick on for 6 hours. and hopefully, the temperature inside the raised bed wouldn't drop too low at night.

As mentioned above I would go for a 12 volt led setup since LEDs are dc and a 120v ac unit converts it to dc anyways. Something like this https://www.amazon.ca/Growing-LED-Light-Spectrum-Lights/dp/B07WJ4BV2D
No idea of that ones  quality but it's similar to the tube ones I have now.
Next would be panels: you can get used 250 watt panels for 30 cents a watt so add more panels.
My two cents,
Cheers,  David

David Baillie wrote:As mentioned above I would go for a 12 volt led setup since LEDs are dc and a 120v ac unit converts it to dc anyways. Something like this https://www.amazon.ca/Growing-LED-Light-Spectrum-Lights/dp/B07WJ4BV2D
No idea of that ones  quality but it's similar to the tube ones I have now.
Next would be panels: you can get used 250 watt panels for 30 cents a watt so add more panels.
My two cents,
Cheers,  David

Yeah, those are good too 8w per meter for 32 watts for a 4-meter strip, I could run 2 strips at 6.5ft all the way down the cold frame bed. I wouldn't run the 120v adapter though because then I would need a dc to ac power inverter as well as a ac to dc rectifier after that which would mean big increases in current draw. Just hook up the 12vdc battery and that's it, 32w/12vdc=2.66A could run these for 4hrs a day for 2 days before needing to recharge, this is actually better than the one I mentioned and may even distribute light better. Hmmmmmmm...

Yes, bigger is always better but I am trying to stay within a budget, meaning cheap, also bigger panels mean more space required and more material to support them. If I buy bigger panels, then I need a bigger charge controller, and I'd be looking at an additional $400 cost to improve what I already have. But yes, better panels would mean I could discharge my batteries further than 10% before recharge, letting me run lights longer, but if I increase lighting wattage, then I would be right in the same spot again lol.

Here is a good study on how DC lights running off an AC grid are actually less efficient than AC versions, and vice versa.

https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1385&context=eesp

It is a chicken and an egg kind of thing. Typically 12 volt panels running on a pwm charger will produce much less power in the winter then a mppt charger unless you adjust the angle constantly. Especially for winter I would invest in a better charger and the higher voltage panel and not be let down later . I had not noticed the leds came with an ac adapter I would not use that of course go straight to 12v dc... the renogy is not bad for a no name... https://www.amazon.ca/Renogy-Controller-Parameter-Adjustable-Regulator/dp/B08CXSPB2Y
Powering a used 60 cel panel like this...

https://www.kijiji.ca/v-general-electronics/belleville/solar-panel/1550306069
Just some ideas for you. Good luck on your project please post results.,  

Found these really cool led lights, 12vdc 3.5w each. could run 4 at 1.16A, 9.4 hrs runtime per day for 2 days. The bright white is 6000k which is good for growing and simulates natural light.

https://www.amazon.ca/AUTOMONARCH-Motorcycle-Daytime-Clearance-%EF%BC%8810pcs-Pack%EF%BC%89/dp/B071RFYB3D/ref=sr_1_44?dchild=1&keywords=12%2BVolt%2BLED%2BLights&qid=1613587695&sr=8-44&th=1

These are also good only 2w each.

https://www.amazon.ca/Kohree-Recessed-Replacement-Equivalent-Motorhome/dp/B07BF4SLGT/ref=sr_1_74?dchild=1&keywords=12%2BVolt%2BLED%2BLights&qid=1613587695&sr=8-74&th=1

I suppose something that hasn't been mentioned here is whether or not it is important what the spectral output of the lights are. PAR - photosynthetic active radiation

This is a really good rgb led light with remote only 2w 12vdc.

https://www.amazon.ca/EverBrightt-Controlled-Colorful-Festoon-Adapters/dp/B01HCUSIKO

We in business managed to get some 6v 220ah batteries, 4 of them. just waiting on wiring and lights to be shipped, and I will be able to test this theory that probably won't work, but I still need the batteries to run a ventilation fan in the summer so it's not a total loss if it doesn't. I've decided to just hook up the batteries in series/parallel to get 12v 440ah, but only drain them a maximum of 5% which would be 22ah of use. the 4.4amps of charging current from the panels will then need 6.2 hours of sunlight over 2 days or in 1 day to recharge, and if they don't get that I will have to charge them manually with a battery charger, at least until I get more panels. I will be able to run the lights for 9 hrs a day for 2 days provided I get sunlight to recharge the batteries.



These are the lights I am going to use, since they are on the right spectrum and very bright, and I can run 6 of them at only 1.2a.

https://www.amazon.ca/gp/product/B0831D5FLK/ref=ox_sc_act_title_5?smid=A1TF0WKG5BQMBR&psc=1

I also will need a timer to time the lights so I found this

https://www.amazon.ca/gp/product/B01MRWKVM0/ref=ox_sc_act_title_3?smid=A2WI2LFG1JAJEM&psc=1

I am also going to connect my solar panels in parallel using this.

https://www.amazon.ca/gp/product/B07S7WHZ73/ref=ox_sc_act_title_6?smid=A9YVKOTFON4VC&psc=1

I hope this works well for you, but my incorrect math not withstanding (forgot its an easy formula of w/v=A, I was just estimating off what could be safely run continuously off a 15amp circuit, 1250w, 1440w at peak), using solar to produce light during the day seems a bit like running a fan to move your sailboat when lacking wind. Here, when it's not sunny we get a lot of rain (105" since April 2020), and I plan to use micro hydro in addition to my storage tanks and ponds as a battery for my solar pumped water. It may be more viable to look into wind in your region. Also, most "winter veggies" are actually grown in late summer-autumn, and just hold tight in the cold dark of winter, not growing much if at all.

It may be worth considering how nature, and people who've lived with it for generations, adapted to cold climates by storing plant energy from summer in animals that fed them through the winter, and then jumpstarted plant growth in spring with their manure, carcasses, and afterbirth from mass calving. I do wish you and your project well, and will learn from your experimentation as I try to get plants started off grid myself without using any more diesel in my genie.

A nice battery pack/power setup:
https://www.youtube.com/watch?v=Fd9quNpOSn0&feature=emb_logo

Mounted my solar panels to my hoop house. I also made use of a hard case I had bought a while back at a surplus store. Turns out it perfectly fits my batteries, this should help keep them warm and my electronics waterproof inside the greenhouse.

This little dc timer switch draws 0.025a in case anyone wanted to know, it is a pretty impressive little switch, you can time 7 days a week, and has several on-off programmable schedules. like if you want something to turn on an hour and off an hour then back on an hour and so on, it can do that, and have it repeat this every day or certain days of the week.

I recharged 17ah of battery drainage yesterday in just 3 hours of sunlight. That amount of drain would be equivalent to running 6 of the led light panels for 14 hours straight. So I think these panels will be able to supply enough charging current for my needs. I don't think getting larger panels is really a necessity.

The batteries were at 12.94 volts when I connected them to the solar charger, now they are at 13v. if 13volts is full capacity, and 11.4 is drained then the math would be as such;

12.94-11.4=1.54

1.54/1.6*100= 96.25 or 96% battery capacity left.

4% less 440ah= 17.6ah

Forgive me if you already factored this in, but be sure to take your voltage readings when there is no load on them. The load will pull voltage down.

Hah, I like the license plate!

John Rosseau wrote:Forgive me if you already factored this in, but be sure to take your voltage readings when there is no load on them. The load will pull voltage down.

Hah, I like the license plate!

Yep, no load.

For some reason, I am not sure why the batteries are at 13.26v with the solar charger hooked up and it is very overcast out, with no sun. Not sure why this is?

John Rosseau wrote:Forgive me if you already factored this in, but be sure to take your voltage readings when there is no load on them. The load will pull voltage down.

Hah, I like the license plate!

I needed a bracket to hold the panels aligned and found an old trailer license plate I had and said you know what I could run bungee chords through the holes and bend this. It actually worked pretty well, I even took the time to make sure the Ontario part was showing at the front.

It is a very overcast day today and my charge controller is putting out .4ma of current which has raised my battery voltage to 13.48vdc no load attached. So this means that even though I haven't had sun for 2 days my panels have still been charging my batteries.

Does anyone know what the best way to connect a solar charge controller to this bank would be? As in which terminals would be best to hook up to the charge controller.

This is how I have my charger connected (top right) which is different than how I had it before, but I think this would be the proper way, according to a video I found on youtube (the guy's hands indicate where the charger should connect). I had the negative on the terminal top right before where it says to ground, which you would think would be the same as the one below, but it is not since I was reading different voltages across each series bank when I switched them both series banks read 13.38v. Very interesting.

I've done it, here are the lights wired up. I am very happy with the output for just 15w 12vdc.











I will take an accurate current reading tomorrow, and mount the lights better inside.