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A DC to DC converter working at its normal ratings is usually about 85% efficient, I am guessing that a 240v Inverter is possibly similar or less and a 240v power supply unit is similar or maybe even worse.
That means you could potentially be wasting 15-25% of your batteries energy in all of these conversions - I dont know what their idel current draws are, but they could be a hidden killer !
If you are going out in the field there may be some benefit to having 240v for other devices, on the other hand there might be a benefit of not having 240v lying around on the wet ground ?
Only you know that.
I chose the DC/DC converter route and made up different leads with pkugs an sockets to suit so they couldnt get mixed up.
Check the voltage requirements of your USB hubs they are more usually 5v DC not 12v DC. (but 12v models do exist - just harder to find).
USB 2.0 Type A sockets are in theory rated to supply up to a maximum of 500mA (1/2 amp- 2.5watts) per socket, but a device has to announce itself as a high current device in order to be able to draw more than 100mA. So the required power for a USB 2.0 hub with say 7 ports can actually be quite high !
Of course if you know for sure that none of your devices draw this much power then you can cut down ?
If its a separately powered device then you are probably quite safe, but if the nly cord is the USB cord then it is also supplying power.
Assuming the Apple power jack is readily available and is just a simple 2 wire, it should be relatively easy to make up your own cable.
If you are removing the PSU's then I recommend that you fuse all lines appropriately for their purpose, otherwise you are bypassing an important safety mechanism.
I recommend that you fuse all 12v lines anwyay inless they are already fused
Hope that helps
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