Getting power while out in the field

That will do the job perfectly. I have a similar Duracell powerpack that is rated 26Ah (that one is 18Ah) and that will power an LED spotlight I have for 3-4 hrs continuous. You can usually also daisy chain these units to a second car battery to extend the performance. If the location is a decent drive away you can recharge it when flat on the journey off the 12V cigarette lighter auxiliary.

The first thing you need to know about that particular battery is that it is rated for 400W. Which means the maximum total wattage you can run on it simultaneously is 400W. All your electrical devices should have the wattage written on them. You simply add all the watts together and if it's less than 400 you are okay.

The second thing you want to know is for how long. This is where Ah (amphere-hours) come in. The linked battery is rated for 18Ah which means it should be able to supply 18 amps for an hour. You won't be drawing 18 amps so in fact this is longer. Your electrical devices should have the amps written on them somewhere. The powerpack for the laptop I am writing on has 100V-240V 1.4A-0.7A written on it. This means that at 100V (or 110V US standard voltage) it will draw 1.4A, at 240V (Australian voltage) it will draw 0.7A. So if I divide 18 by the rated amps I will get an approximation of how long the battery can power it. So for the 110V battery 18/1.4 = ~12 hours. This duration would double with a 240V source.

So if I add a couple of GH2 battery chargers (0.2A each) and an LED spotlight I have (7.2A) then the total draw would be 7.2+(2x0.2)+1.4=9A. I could run all these simultaneous for 2 hours off an 18Ah 110V battery. Or just the laptop and two chargers for 18/1.8 = 10 hrs. The reality might not add up as neatly as the math and the battery may not perform to cited specifications. In fact testing with my power meter the real current draw of every device I've measured has been at least 10% out. But you can get a pretty good idea of what to expect with the math and the equations are about as simple as you get.
 
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I just read some of the comments on that amazon link which highlighted a couple of concerns. That model seems it does not automatically turn itself off on a charge cycle. The 110V Duracell Powerpack 600 that I bought off amazon does.

The other thing to look out for is whether the battery outputs a pure sine wave or not. The pure sine wave inverters put out a much cleaner signal. The Duracell I bought does not and I suspect the Wagan doesn't either. It will be okay for most applications but could reduce the lifespan of analogue circuits in particular. Pure sine wave inverters do cost a little more but produce a much better quality of power. For example the LED light I mentioned makes a quiet buzzing sound on the Duracell that is absent on the wall socket. Mains power is pure sine wave, the Duracell battery-inverter is not. Another term for this that might be used on the box is as either sinucidal (pure sine) or non-sinucidal.

Locally here there is a brand called 'Power Tech' that makes a battery-inverter (the proper name for the device you are looking at) that is pure sine wave and that will be my next purchase (plus the locally sourced one is 240V which will last longer than the 110V Duracell I bought off amazon).
 
Honestly, a small modern putt putt isn't a big deal if you hide it behind the mass of a car or van a ways off from set. And it'll give you a level of security and confidence, that no battery-based solution can match.

Plus they cost bugger-all to rent.
 
And you could also consider solar power, check out your caravan accessory place for a whole range of options. Egg, sine waves don't come into it, he's stepping down 12v DC to DC, not up to 50Hz.
 
Not necessarily. I thought the same thing when I bought mine but that will only be the case if the equipment has the 12V 'cigarette lighter' plug. With many devices such as a laptop charger the jumpstart battery will convert its native 12V DC to 110/240V AC and the laptop charger will then convert back to 12V DC. All the devices I use with it are 12V but run off mains power in this way. The only reason to not get an adapter to plug these devices straight into the car's 12V is because if you're off the beaten track you want to be able to get out of there afterwards. And one of the jumpstart batteries (especially with the air compressor built in) can give you a lot more confidence to 'go bush'.

The other option is the small portable generator that Grug mentions (which I am considering) of which there are many reliable chinese clones of the Honda 2000i at the moment that only cost half again as much as the battery-inverter. I have also investigated the solar option at the advise of a caravan-crazy work colleague of mine which are tempting but more expensive again. But I do like the idea of solar. The other advantage of having any one of these technologies is not sitting in the dark during a power cut. I am the last house on my grid so every single time the power company does any maintenance or repair my power goes off (and the bastards kick out all my retic sprinklers). While my neighbors are in the dark, I'm watching tv.
 
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