Ok I'm bored, so I did a little investigation
I'm no electrical engineer, but based on my rudimentary understanding of power consumption and the specs provided in the links I posted here for what you need, here's what I figure you need for running a 400W HPS light for flowering 12/12. Maybe someone with more knowledge can check my calculations
So you need a battery like this:
hxxp://www.canadiantire.ca/browse/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524443277145&FOLDER%3C%3Efolder_id=1408474396676726&bmUID=1224645716938
$120 - This is a 6V battery and provides 390 minutes of use at 25amps. They also weight 62 lbs each
A HPS hooked up to this would draw 66 amps:
Amps = Watts / Volts
66A = 400W / 6V
So, to find out how long this would last, you need to get a conversion factor:
25A(x) = 66A
x = 2.64
So:
390 minutes / 2.64 = 148 minutes running time (say 2 hours to be safe).
If you are running a 400W for 12 hours, that is 6 batteries to run it. Total cost: $120 x 6 = $720
Of course, these need to be charged, and if you are doing it from the house power supply, well you just have an expensive middleman. You are still paying for the electricity to charge the batteries.
To get around this, you need a "free" source of power. Let's go with solar power.
80W Solar Panel:
hxxp://www.canadiantire.ca/browse/product_detail.jsp?FOLDER%3C%3Efolder_id=1408474396676726&bmUID=1224645328347&PRODUCT%3C%3Eprd_id=845524443281866&assortment=primary&fromSearch=true
These run $750 each, and you would need 5 to power a 400W HPS light while it is in contact with full sunlight for 12 hours a day without batteries. Of course, the seasons change the amount of sunlight that is available during the day, so if you are growing all year you need to figure out worse case, which would be the day of the winter solstice. In Toronto, this equals about 9 hours of sunlight.
According to the specs, you need 150 amp hours to charge a single battery. Our solar panels are 80W, charging a 6V battery, so:
Watts / Volts = Amps
80W / 6V = 13A
So each panel generates a steady 13 amps (in full sunlight). You need 150amps fed to it for an hour to charge, and we have 13 amps for 9 hours, or 117amp hours. Remember from above we need 6 batteries for our 12 hour period, so:
6 x 150amp hours = 900 amp hours to charge our 6 battery setup. This requires 900AH / 117AH = 7.69 panels, rounded up we need 8. They are $750 bucks each, so that will run you $750 x 8 = $6000.
So there you have it! For around $7000 in the northern hemisphere, you can buy yourself a free supply of energy! In reality, it is going to be more than this, since you will not get full sunlight 100% of the daylight hours, the intensity of the sunlight will change with the seasons, and you probably need some sort of sun tracker to make sure the solar panels are always pointing at the sun or compensate with more panels. So I'll throw out a number and say you need $10K for each 400W light you want to run. We haven't even talked about 18/6 or 24/0 for the veg period....
Or just grow outdoors :hubba:
