Do you really need an AC inverter?

#46
You've changed the criteria. The original question was about the need for an inverter and anyone would reasonably say no. You can often find a 12 VDC appliance and doing no conversion is the best option. That is a good thing to point out, but you had a conclusion to support in your posit.

Several people pointed out that sometimes there are things that can't run on 12 VDC or doing so would lock you into niche product or custom solution. You acknowledged that battery chargers and laptop adapters are common reasons to need something other than 12 VDC.

You'll need a conversion and whether you select a DC boost converter or an inverter isn't going to matter much. The primary loss of efficiency is due to the large switch on the primary source and that's going to be present in both cases. Once you've chopped the 12 VDC with a large FET and stored energy in a big inductor you've lost the majority of the energy you're going to lose, so the additional loss from choosing to rectify back into a higher voltage DC or create an AC output is marginal (and the current bleeding edge transformer-less inverters are essentially exactly the same as an equivalently sized DC converter).

So *if* you can't find a 12 VDC solution for a given power requirement what drives your losses is the quality of the converter and sizing it right. Selecting a poor quality modified square wave inverter running at 10 KHz that is lightly loaded will result in a lot of lost power. Selecting a true sine 400 KHz PWM inverter that you run at 80% of load rating won't. The same is true of a DC boost, though. If you size it right and it's running completely in continuous mode at the peak load it will be good while putting 10% of the rated load, forcing the switcher to go discontinuous and shunt power to remain in regulation might reduce it's efficiency to 1/3rd of its peak efficiency.
Great discussion can easily change criteria of the original intent, but that is assuming I had intent, of which, I didn't. Just stirring thought, in a giant think tank to hear different views.

In an ideal world, we could have uniform power, without conversion, but as you mentioned, some are and/or aren't better than others.
 
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#47
I would say we don't "need" 90% of the crap we drag with us , don't need a rtt, don't need a camp kitchen , don't need a fridge , don't need tablets and cameras and ect ect . but if it's something you feel to be useful to your situation and style of traveling then by all means use it . I keep a small inverter in the tahoe and it's come in handy a few times when a car charger has been forgotten or I needed to use a corded power tool in a pinch . yes I could buy some other tools that are cordless but that's money that could go to getting out and exploring .
Working from a base, you need less, but if you are on a true expedition, you will be very far from a base, and you needs will change accordingly.
 
#49
One thing that I haven't seen discussed here is: what if someone else on the trip has a device that has a unique AC battery charger and you want to charge it? I carry one or two very small 150W inverters for computer, cam batteries, etc. They travel in a bag buried behind the driver's seat and I haven't had to use them in 5 or 10 years, but they're there if needed.