hah
For several reasons I do not use a standard vehicle alternator to charge.
1. Alternators are basically power supplies and do not charge a battery properly, about 65-70% full is the most you will get from standard alternator charging.
2 and perhaps worst is that say you run a decent charger and properly charge the battery, any journy you make will discharge the house battery down to the same level as the starter battery.
Because you should never discharge a house battery below 50% say you start with a 100 Ah battery if its charged to 65% take away the 50% not to be used and you end up with 15 miserable amps
I agree though that all elec systems should be grounded mains and ultra low voltage battery systems.
Here is some info
http://www.caravanandmotorhomebooks.com/books/motorhome_electrics_caravans_too.htm
Here is a test I did to prove that a fully charged battery lost some AH when connected to an alternator system
From fully charged at 12.93v (measured 12 hours after coming off the Sterling charger) connected bulb, it took 6 hours and 17 mins to reach 12.2v (ie flicking over backwards and forwards from 12.3v)
It was then fully recharged on the Sterling, allowed 13 hours to settle the voltage, reading was 12.94v flash 12.93v, the engine on the iveco was started, then I connected the battery using a good solid cable as before and drove this morning for 1 hour 14 mins, as soon as I got back it was connected to the same bulb (55w halogen) connected at 12 : 12 today, it started flashing between 12.3 and 12.2 at 5 : 37 PM today
Same battery, same full charge by Sterling, only difference 1 hour 14 mins of extra "charging" as knocked off 52 mins off usable power !!
The Sterling charger is a top quality 30A 4 stage inteligent charger, which also acts as a power supply on hook up/shorepower, made for marine use it will accept input power from 80 to 440v and 40 to 400hz so will work from any power supply in any country.
If I was ever going to charge via a vehicle I would add a smart regulator to the alternator and a split charge diode so the 2 systems stayed completely isolated.
And I would still ground all equipment and metal work, its the safest way, I would never use it as a feed though for the reasons already stated.