With lead acid batteries, you cannot use the full capacity of the battery. In practice, you can typically only use about 50%-60% before the battery voltage drops too low to be useful.
In addition, even if you only use 50% of the rated capacity, you will kill the batteries fairly rapidly. If you limit yourself to 30% you will get a much longer lifetime out of them.
Using quality deep cycle batteries (think fork lift batteries) will help with as far as how far down you can discharge them, but they still do not like being deeply discharged and will die sooner and degrade faster the more deeply you discharge them.
If you get quality deep cycle batteries, I would not count on more than 50% discharge and 30% will be much better. That means you need more batteries to do what you want.
The other thing to remember is LED’s light output is directly related to voltage - in a non-linear way.
Once the voltage drops below around 2.55 volts/led, they just stop working = zero light output. Max voltage is typically 3 volts or a hair less, so you dont have a large swing for usable voltage range.
If you are direct driving the LED’s from the batteries - with no drivers, regulators etc, that means you can only have about 15% drop in voltage before the LED’s turn off completely. Even with as little as a 10% drop in voltage, the light output will drop by a factor of around 6. So, when you batteries are discharged by 10%, your light output will be dropped by about 85% in round numbers. When the voltage drops by 20%, you will have zero light.
The only way around that is to use drivers designed to work with a 10-15 volt input. I dont know of any off the top of my head.
Here is a voltage vrs current vrs lumins output for the LED’s used in many grow lights - including SolStrips. Most LED;s in use with grow lights will be very similar.
I wasnt very clear with the two points I was trying to make above.
You need more batteries than you think - by at least double.
You will be far better served if you can find LED drivers designed to work specifically from 6 or 12 or 24 volt batteries. Direct driving is not going to work nearly as well.
One other detail - you are going to need to re-charge those batteries fully - every - single - time - you discharge them. If you dont, they will die even faster. Lead acid batteries do not like being left discharged for any length of time.
Also, when you decide how many solar panels you will need to do the re-charging, you have to remember that they are rated based on full sunlight, at hi noon, with the sun directly over head.
What that means in real life is that you probably need more like three times what you think you need to re-charge those batteries - and that assumes pretty clear weather, no shade trees, no dirty panels, etc etc.
In other words, early OR late in the day, any solar panel will only put out a small % of its rated power. You will typically average more like 30% to 50% over a full day - but only if its sunny and clear.
you could try something like the 12/1 light cycle… veg is 12 hours of light, 5.5 hours of dark, 1 hour of light, then 5.5 hours of dark and flower is 10 on 14 off…
this guy even says for those 12 hours on you can run 15 mins on, 45 mins off 12x, 5.5 off, 1 on, 5.5 off for a total of only 4 hours of electricity per day with no negative impact on vegetative growth… although i’m not sure how true that is lol. and then 10 hours of light should be sufficient for the flowering stage…
should basically just be able to interrupt the dark period for one hour in the middle to maintain vegetative growth
for flowering to begin it needs an extended period of darkness for all the phytochrome far red to convert to phytochrome red, interrupting it with an hour of light is sufficient to raise the levels of Pfr back up and prevent flowering.
likewise in flowering i’m sure you could run 15 mins of light. 45 mins of dark every hour for 12 hours as long as it has an uninterrupted period of darkness, interrupting the dark cycle is what will stress a flowering plant. photosynthesis would prob suffer though.
@Hoodini if you have 10 hours of daylight maybe you could run 2-3 hours of supplemental light then far red lights for a few minutes to initiate sleep faster. i’m not sure how many batteries you have
That’s all very useful information thanks everyone but I’m gonna be running auto flowering plants this winter so there is no keeping them in vegative growth so I don’t have to worry about that. Still all very useful info
I have 2 6v rolls 410 ah deep cell solar batteries D.O.D is 80%( I’ve been living on solar for 10+ years I’ve tried all kinds of batteries) 500w of solar paneling ( taken off my home system) I also have a 2000w inverter but I’m trying to keep it 12 volt if possible because 500w of solar paneling won’t be enough if I invert to 120v. I really don’t need 8+ hours of lights after dark just anything more than 10 hours of sunlight will help I could probably push a 600w hps bulb for at least 4 hours
In your situation i’d use the inverter to power a couple of 250W digital ballasts and have 2 dual spectrum 250W lamps with small hoods so they don’t block much sunlight. I’d run the lamps for a couple of hours at the start and end of the day and the batteries would have around 6 to 8 hrs to recharge between discharge periods. If funds allowed it later i would change to high powered led cobs strung up high so they don’t shade the plants from the sun.
It just sounds silly to me to use AC and ballasts when LED and 12v just go hand in hand. That has the potential to be quite efficient (and likely more than budget allows). I doubt that the extra light will be worth it in the end with autos. Just plant a few extra plants and use what nature gave ya.
Haha thanks man That’s what I think I’m going to for now and put my money into my greenhouse and I’ll always be able to upgrade it later. Thanks everyone great info!!!
In a greenhouse, all you would need is to extend the photoperiod to prevent them from flowering. No artificial light can compare to real sunlight. How big is your greenhouse? You are able to keep 28 plants vegging in an area of 15’x15’ using 7 to 8 2’ fluros 20watt each. The most important thing about that is not the light itself but to be able to prevent bugs from going in there at night when the lights are on. This is impossible if you don’t have a sealed netting
Yeh led would be way better but to get him up and going for around 400 dollars is not going to be that easy If he is decent with his diy electrical skills he could rig up some 12V cobs for about the same money though eh
