Not exactly programming (sorry) but I think it's pretty close and can be of interest to other programmers.

I'm trying to setup a battery power station so that I can work from anywhere. I go surfing a lot and my idea is to be able to work from wherever I can park my car (given there's coverage). So, I'm getting a deep cycle battery, a 240V charger (I'm in Australia), and an inverter.

At the back of my laptop it says 19V and 4.62A. From the people I've spoken to that means it consumes about 90W at most. So my inverter needs to be able to output about 100W. Most of them seem to be 200W and up so this shouldn't be a problem.

I want to be able run my laptop for 10 hours (plus the 2 hours I get from the laptop battery) straight. According to the people I've spoken to and from what I gather online I need a battery that has the amp hours for my "amp draw". I have no idea how to calculate this but I've been guesstimating.

Most deep cycle batteries seem to be classified using amp hours (Ah)... 35Ah, 50Ah, 75Ah, 100Ah, and so on. However the amp hours on those batteries is for a 240V and I seem to be using 19V. According to an expert I spoke to you'd need a 100Ah battery to power a 5A appliance at 240V for 10 hours (you only get about 50% useful power). That to me is 5A * 240V = 100Ah battery.

So, naive as I might be I take 240V and divide that by my 19V and reach the conclusion that I can get away with a battery that's about 12 times smaller than that 100Ah. The expert told me I needed a 50Ah battery so that's probably what I'll be getting, but it would be interesting to know what I theoretically would need to power my laptop for 10 hours.

As for charging the battery the expert I spoke to said I needed a 3-5A charger to be able to charge that 50Ah battery from flat to full in about 10 hours (I will just leave it plugged in over night).

Now to my question. The expert said it's not a matter of "if" more like a guaranteed "when" my computer will stuff up if I don't use a "pure sine wave inverter". From what I gather the power that comes out of that battery is not as clean as the power we get in the socket at home. Apparently it's "square" and the one in the socket is nice and smooth.

I've already got an inverter, but it's not "pure". Do I really need to buy the $200-300 pure sine wave inverter or can I get away with something else? Perhaps the laptop adapter that sits in the middle of my laptop power cable already fixes that wave to be nice and smooth?

Thanks!