Portable Grow Box ?

I'm planning on building a portable grow box. Optimally, I'd have a power outlet near the box. However, certain situations may require a BATTERY.

Stay with me here. I'm trying to make sure this would work. If I have a 40-watt CFL, and (hopefully) a 12v lead-acid battery, that means I need 3.33 amps coming from this battery to light the CFL. (40/12=3.33)

If I need this battery to last for 7 hours, that means I need (3.33 * 7) a 23.31 Amp-hour, 12 volt battery.

I just want to make sure my math is right before I shell out money for a 12 volt/35 Ah lead-acid battery. Can anyone suggest any alternative batteries/systems? Also, does anyone have experience running CFLs from DC current?

Thanks.

sounds like too much messing about, and if your not there every 7 hours.
they will go hermie

Well, it's for a car ride and for emergency situations, really.

just use a 250 hps and an old closet.
dont make it harder for yourself,than it already is.
try to keep things reg. and simple.

mithra94 said:

Well, it's for a car ride and for emergency situations, really.

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what happenes when your flowering?
are you going to use flo's for 12/12?.
powered by a batt., that needs charging every 7 hours?.

Honestly, I'm set on doing this. My point was not to ask about the idea, but rather if anyone can double-check my calculations to make sure I'm rating the battery requirement correctly.

This isn't for flowering, I'm going to be plugging this unit into the wall outlet when I reach my destination.