Using a deep cycle battery - inverters?

[Captain Goddammit]

Here's a repost of something I wrote a few years ago that ought to help:

There's a lot of questions about batteries, power, watts, amps, etc. and it's all Greek to lots of Burners unless you happen to be a bit of a tech-head.

I've got an analogy that may not be technically perfect but it'll get you a lot closer to understanding WTF it all means.

The formula is volts times amps = watts.

Power (watts) is the total amount of work being done. So think about something almost all Burners are familiar with: BICYCLES!

The total Power is the bike moving down the Esplanade at say 10 MPH. Think about the speed you are pedaling as your voltage, and how hard you push on the pedals as your amperage (current).

You could accomplish that 10 MPH down the Esplanade by pedaling really fast, in low gear, and not pushing very hard on the pedals. That's like higher volts, and fewer amps. You could also accomplish the 10 MPH ride down the Esplanade by shifting to high gear, pedalling slower but pushing a lot harder on the pedals. That's like low volts, but higher amps.

This is why you need larger wires for low voltage but high current power use; lets say you're really super strong and leave your bike in top gear when pedaling through super soft playa, dragging a wagon full of beer. You'd have to pedal really hard - but at low speed - and you'd need a strong chain, strong pedals, strong crank, etc. to handle it. You'd need big stout wires to handle all those amps.

You could also shift to super-low gear and pedal really fast, but much more lightly. You wouldn't need as strong a chain, pedals, etc.

Low voltage doesn't shock you when you touch it; you can grab both terminals of a car battery and feel nothing. Take that same battery, run it through an inverter that steps that same battery power up to higher voltage (but less amps) and it will shock the daylights out of you if you touch the wires coming from the inverter.
It's kinda like if you're pedaling your bike really hard but slowly (high amps/low volts) and someone stuck their hand in the way of your pedals. It wouldn't hurt, you'd barely bump them. If you were in low-low gear pedaling softer but really really fast and someone stuck their hand in the way of your pedals, they'd get whacked.

So... volts times amps equals watts. Watts is the total power.
100 amps of current draw at 12 volts is 1200 watts of power. And it would require some BIG wires. This is why power companies use super-high voltage wires to transmit power over long distances. Lower voltage would require giant wires to send the same amount of power.
10 amps at 120 volts is the same 1200 watts.

Amp-hours is simply how long something (like a battery) can deliver power. A 12-volt battery that is rated at 100 amp-hours theoretically can put out 100 amps (at 12 volts) for one hour. Or, it could make 10 amps for 10 hours. Or 1 amp for 100 hour

[Traveller in Time]

Hi. I have a 2k watt inverter. Connected to a deep cycle which is connected to car battery. I run a 700w tv and a small flat screen. Can I run a DC batt with a auto battery? Or do I need to use a 3 bank DCYCLE battery all connected?
Thanx

Besides the don't mix batteries you will also need big wires to feed your converter. I would suggest to use only a few inches of wire between the converter and the batteries. Hmm, curious about what FETs (high power electronic switches) are used in your converter. Switching some 150A is not an easy job

2kW ~~ 2000VA >> an average car battery would not last ten minutes and be drained beyond repair.

[bradtem]

I wrote this article many years ago but it's still mostly correct, and people have found it useful:

http://www.templetons.com/brad/burn/burn-power.html

Since then, inverters have gotten cheaper and better. Even so, I have often come upon small TVs/computer monitors that use an external DC power supply. If you find one that takes 12v you could run it directly from your battery, which will be more efficient.

Yes, get deep cycle or RV -- your cheapest bet are the RV/marines at Costco. They should run your 70w TV for about 10-12 hours for the cheaper one, but you don't want to drain the battery all the way. However, if you have a way to recharge you will be fine. These are heavy -- 80 to 100lb -- so you must really be keen on watching your TV.

Or did you really mean a 700w TV? There is no such thing today so I presume you mean 70w.