If I set up a pc to run from solar charged deep cycle batteries, can I bypass the power supply of the pc (remove it) and supply the different required voltages from these batteries?

This seems to me to be a much more simpler set up than converting the 12 volt power from the batteries to 240 (in .au) through an inverter and then transforming the 240 back to 12 (and 5 etc) through the power supply of the pc.

If yes, does anyone know of a suitable Howto?

I have used those batteries in the Western Australian outback, the 12 volt batteries used to give a steady 12.8 volt (adjustable through a regulator) from which I used to run a Toshiba 486 laptop and a printer, as well as the lighting of a camp.

The purpose would be to keep the pc on when there is a mains failure (blackout).

Thank you for your help.

Yes, by using a power supply designed for 12VDC systems. Google for PC car power supplies.
Of course you could design one yourself too.

It seems that the 12 volt could be used directly--possibly with one or more series diodes to put the voltage in the right place.

I would think that you would need down-convertors for the lower voltages--especially the CPU power.

You may want to use your favorite search engine with Dan's Data for the search I remember reading a couple of questions on there about this type of thing.

...if you bear in mind that you are trying to do the same sort of thing that an UPS does, you might also choose to ask yourself the question "Why not use an UPS?"

Assuming that the answer is something like that you would prefer the DIY route, then you can. Remember that you'll probably have to produce most or all of the rails that a normal PSU does, you can start by looking at the ratings on a typical power supply. If efficiency is an issue to you, you'll have to use switching power supplies, but to be honest, these are a real pain. Alternatively, linear supplies are easy (watch the power ratings!) but inefficient. This may be a very reasonable trade-off, particularly for the lower current rails.

Thank you all - great stuff.
I will investigate it all.