Battery Question ; time watching TV

Since I've often done something similar with a computer+monitor+sat dish+receiver, I can tell you these time estimates are about right. So I want to commend the well-reasoned and informative response from RJ, which caught many of us off guard!

For the OP, I would add that your battery life is roughly equivilent to the weight of your batteries. There is no lighter weight, easier way to do what you are doing. If you don't care about the battery you can drain it completely empty but only do that a few times before you kill it dead. This is why the calculations here figure on you using only half the capacity.

If you buy more expensive "AGM" batteries you can drain them deeper without harming them. They also do not give off deadly gas when being charged or overheated, so they are safer.

If you want an easy+simple but expensive option for doing this, google "goal zero". I use one of these when I'm tent/car camping and am very happy with it.

RJsfishin wrote:
What was it about this post that we didn't understand ??

RJsfishin wrote:
We can come perdy close.
You are going to be drawing about 125 watts total incl inverter, tv and DVD
125 divided by 12 volts is about 10 amps from the battery. Having 50 AHs available from a 100 AH battery, you will go about 5 hrs

Nothing. By the time I started writing I didn't recall there was a post that gave the complete picture. But yours did. Although we don't know the Amps he's drawing, but he can plug in his numbers.

What was it about this post that we didn't understand ??

RJsfishin wrote:
We can come perdy close.
You are going to be drawing about 125 watts total incl inverter, tv and DVD
125 divided by 12 volts is about 10 amps from the battery. Having 50 AHs available from a 100 AH battery, you will go about 5 hrs

The Snowman9000 estimate is good but I'd say plan on 10A and about 4 hours.

After that it depends upon how well the battery is recharged. If you are out driving your car and get the battery fully charged then great another x hours, otherwise less.

Summing up various correct replies...
Add up the watts or amps the items use.
If amps, multiply by ten to get amps at 12 volts.
If watts, divide by 12 to get amps at 12 volts.
The sum will probably be higher than what will actually be used, but anyway.
The inverter will consume additional amps, maybe it balances out with the previous over-estimate.

Let's say it is 72 watts / 12 volts = 6 amps.
For an hour, that is six amp hours.

Group 24 & 27 batteries are 85 & 105 amp hours respectively. Don't run them to empty or they won't last long. So depending on how you want to treat your battery, at 6 amps you could do 8, 12, 16 hours?

Hopefully this is good enough info.

Jeez, what is happening to this forum? What a bunch of crabby "get off my lawn" old men. It's not funny, it's shameful. If you won't help the man, then keep quiet.

35w sounds high for the tv, is this an older unit? my 28" vizio led draws 9 watts, can't imagine a 35-40 taking nearly three times that.

how old is your battery, and what does it say on the label for "AH", "amp-hours"

yes, I was being a wise guy in my original post, but there are a lot of variables involved that affect the outcome. for example a six year old battery isn't going to give anything close to it's rated capacity, which means your TV time is cut short versus the best estimates anyone could provide without the information.

Al leaset one movie, probably two.

tonymull wrote:

tplife wrote:
Planning it out beforehand would provide a lot longer viewing time. The largest 12V HDTV would be the 32-inch Jensen, $ 417.55 new. An Optima or Lifetime or whoever's AGM battery would tolerate deep discharge and offer a lot of other advantages over an old-school lead acid as well. The 12V HDTV gets you away from inverters that waste a lot of power to convert, rather than a converter, which wastes a fraction of power vs. an inverter (i.e.; convert a 19V laptop to 12V).

32-inch Jensen HDTV

Yep, TV's all run on DC. That brick in the cord converts AC to DC. If it's not in the cord it's in the TV itself.

And he said up front he knows very little about electricity. Probably wouldn't be good to give him a handful of alligator clips and turn him loose..

This has to be a joke.