16 x 75 watts is 1200 watts. Since you mention four
batteries,I'm guessing you figure to set up four
lamp poles with four lights each.

4 x 75 watts is 300 watts. At 12 volts, that makes
for 25 amps. I guess you could run 10 gauge copper
wire, that's not too awful.

I remember from some where, it's not wise to discharge
trolling batteries lower than 50% at most. So, the
90 AH batteries would provide "about" two hours of
run time before damaging the cells.

If you rigged a cable from the trolling battery to
the battery (charging system) of a running car,
you could extend the light time, a LOT. Might not
run till you were out of gas, but it should extend
the runtime.

Sounds like a fun project. Hope you tell us how it
all works out. I'd still be thinking in terms of
gasoline generator, some how.

..
Christopher A. Young
Learn about Jesus
www.lds.org
..

On 9/26/2013 9:04 PM, sms wrote:
The marching band at my son's school needs lights for the practice
field. We've been renting lights for about $2600 for five weeks, not
including fuel for the generators. This is for two 4000 watt lights (4 x
1000W bulbs).

We'd like to find an alternative, even if we have to spend three-four
times as much as five weeks of rentals cost. We don't actually need 8000
watts worth of light. We need lights for two hours a day, two days a
week. There is no electricity available at the practice field.

My idea is to purchase sixteen 4000 lumen 75W 12V HID flood lights, four
90AH deep cycle batteries, and eight 18' light towers. This would cost
about $4000. The batteries would probably need to be replaced every 3-4
years.

I was looking for some other ideas on how to do this.