can I run a laptop on a 12VDC 'car' battery?

Hi, I read a few threads, mostly a few years old about running laptops from 12VDC 'car' batteries.

Can it be done? Looks like it, but then the posts were before Li-Ion batteries were common. I understand that Li-Ion batteries have a devoted charging circuit, though this is only what goes around the grapevine?!

Also, people on this Forum name various computers of the period that worked fine on 12VDC back in 2007. Even then, they described them as 'older computers', so please don't mind me bringing this up again.

Googling tells me that there are LOADS of boat users who, like myself, are in need of a computer (laptop or tablet) that draws little power and runs on 12vDC without the need for either an inverter (= extra power consumption) or voltage increasers (say to 18.5VDC for many newer laptops). Both are an item extra to go wrong at sea, so a more direct approach without extra electronics is very desirable to us.

Googling also tells me that there are no, or very few, designated 12v laptops available.

The aim of the game is to buy 1 or even 2 or more low-spec laptops so that there is always a spare in case one gets 'washed' by accident. The computer is a valuable resource that can run loads of safety equipment on long/short handed voyages.

So, I have a load of questions really:
1. Is having a 'modern' Li-Ion battery a problem if one just sticks an average laptop that runs at or near 12vDC straight on to a 'car' battery? (with a fuse) or are there issues with it?
2. Are there any laptops (specific models) available that anyone knows of that are cheap as chips but reliable, which may be suitable for the job in hand.
3. Does anyone have any idea why it's not widely known that laptops CAN seemingly (from reading this Forum) run on 12VDC. Because other teccie sites (from the computer point of view, not from the electronics point of view) seem to jump up and down with anxiety at the very idea of trying it.
4. Is there any advantage in charging the battery seperately rather than running the laptop with the battery in it, practically? How would one do that from a car battery to be sure it doesn't get too much charge too fast?
5. Most batteries seem to be about 10.8 VDC (mine's 11.1VDC even on this machine wihich has a 18.5VDC output powerpack!). Why is the voltage so different and can I therefore run this machine from a 12VDC battery? Do I need a 'smoother' or controller or the like? Please note that this machine has a 3rd pin in the charger and supposedly uses intelligent charging, whatever that is. Is that a gimmick or does it have real application and does it make any difference to running on 12vdc?

I know I'm new here and have loads of questions, so please forgive me, there seems to be so much taboo about this, so I am really trying to get to the bottom of it in one fell swoop and hopefully good answers will be able to help loads of other boat (etc.) users.

Cheers!