Tailgating with Directv, Inverter, How Long?

[reverett1522]

Searched and couldn't find the exact answer to my question... I will be tailgating and in charge of the TV. We've used generators in the past but it's not available to me this year. I want to use my deep cycle battery (80 Amp Hours) and an inverter to run my H20 (45W) and my 32" LCD (300W (2.5 A x 120V). Probably going to use a 750 watt inverter to be safe.

My question is how much viewing time will I get out of this set up? I've seen calculators on the web that say anywhere between 2 and 4 hours. Hoping someone has done this before and has some real world experience. I'll need it to run for 4 hours, will this work or should I look in to a second battery? I would like to avoid having to run the truck motor because of the exhaust.

Thanks,
Rob

[n3ntj]

Just using basic math and electricity formulas, you should be good to go with those specs. I assume the battery is 12v?

[aim2pls]

easiest way .. is to test it .. if your definately going this route ....

[davring]

If the inverter were 100% efficient(which it isn't) 350 watts at 12 volts is a 30.0 ampere draw. You would have approxamately two hours. A better spec on the battery would be to find its reserve capacity. Usually rated at a 20 amp load, it would tell you how many minutes the battery could maintain 11.2 volts with that 20 amp load applied. A deep cycle battery would be preferred and not a cranking battery.

[carl6]

easiest way .. is to test it .. if your definately going this route ....

I would definately test it, not only to determine battery life, but also to make sure both the H20 and TV are happy with the inverter power. Not all inverters are created equal, and the lower cost ones produce a pretty noticeable square wave. A high quality marine or rv inverter should produce a better approximation of a sine wave. For a 1000 watt sine wave inverter you would expect to pay upwards of $300 or $400.

My guess is you will need at least two batteries to last 4 hours. And that might be pushing it.

Carl

[captain_video]

Have you considered a portable generator?

[jfalkingham]

beyond getting a portable generator, you can always use your truck as the generator.

Run it for a bit mid way to keep the juice going, have a fully charged backup or a battery booster if your main won't start the truck up post game. I've done this for a year for NASCAR and NFL games, but finally bought a 3500 generator easily handles
the tv and sat, but can do the coffee maker, AC, and other comforts of home in the camper.

Have fun!!

[techntrek]

So you'll be using 2.9 amps (per hour), probably less since the rated amps are usually on the high side based on readings I've taken with my Kill-A-Watt meter. You should never use more than 50% of the rated capacity of a battery, so that gives you 40 amps of usable capacity. 40/2.9 = over 13 hours of run-time. Your inverter should be rated to handle 2-3 times the running amperage for start-up surge. It doesn't have to be rated at 2-3 times, only the surge rating, which is usually good for several seconds.

HOWEVER, if your inverter is NOT a true-sine-wave inverter, I would be very cautious about using it on this sensitive equipment. I have seen electronics burned out very quickly when a square-wave inverter was used (personal experience).

[houskamp]

So you'll be using 2.9 amps (per hour), probably less since the rated amps are usually on the high side based on readings I've taken with my Kill-A-Watt meter. You should never use more than 50% of the rated capacity of a battery, so that gives you 40 amps of usable capacity. 40/2.9 = over 13 hours of run-time. Your inverter should be rated to handle 2-3 times the running amperage for start-up surge. It doesn't have to be rated at 2-3 times, only the surge rating, which is usually good for several seconds.

HOWEVER, if your inverter is NOT a true-sine-wave inverter, I would be very cautious about using it on this sensitive equipment. I have seen electronics burned out very quickly when a square-wave inverter was used (personal experience).
you forgot that the 2.5 amps is at 120v not on 12v.. so devide that time by about 10..

[techntrek]

Whoops, you are right, I forgot that part of the math. A night with little sleep is my excuse. I also didn't factor in inverter losses (too minimal to have an effect in this case) and that power factor usually doesn't give you a perfect 1-to-10 conversion. But again, not something that you have to worry about for back-of-the-napkin conversions.

So you will only get around 1.3 hours of run-time with that battery, a little less when you subtract some of the losses I mentioned above. Figure on an hour for a nice round figure.

[Doug Brott]

Seems like something like the Quiet KIPOR Digital KGE1000Ti Gas power Generator (http://cgi.ebay.com/New-Quiet-KIPOR-Digital-KGE1000Ti-Gas-power-Generator_W0QQitemZ200131248182QQihZ010QQcategoryZ 16039QQcmdZViewItem) might work. It's not free, but might prove to be more reliable and cost effective in the long run.

This unit claims to be less than 60dB @ full load - put it on the other side of the car and you probably won't even hear it.