+1 on carrying a charger - don't forget the extension lead!
(hope your trip went well and the alternator didn't shyte itself, since this thread is a couple of months older now ... !)
once you get sick of roughing it and start using powered sites, they come in bloody handy to keep the freezer frozen and the cranking battery up to scratch :)
i picked up a 2 amp charger from the auto-shop in derby - it was a simple thing without any fancy-pants charge control: we'd plug that sucker into the aux battery to keep the freezer happy, and when the volts got back up to a certain level the isolator allowed current into the cranking battery as well.
9-12 hours of 'slumming it' worked out to be just enough to get the freezer to -20 and the volts in the 2ndary to 13.x
this is the isolator we installed, ~$120 jaycar:
http://www.nissanpatrol.com.au/forums/
jaycar 12v 100amp isolator MB3680
we used heavy-guage speaker wire to join the aux battery to the isolator & the isolator to the primary battery - i ran the wire in the cable guttering and installed the 2ndary in the back of our wagon - one of these days i might even change it to some sort of sealed battery; but for now, we're just using a wet-cell deep cycle which has served us well 2yrs and counting
getting back to the original topic, my understanding was the regulator also converted (3phase?) ac to dc by 'clipping the wave' - ie, only allowing current to flow out into the 12+ vdc line at a certain voltage range
as to 'how much' is output, three separate considerations affect this:
a. as the charge stored in the battery increases, the overall system voltage downstream of the regulator increases
b. alternator-regulator magnetically affects slip-rings that shift the rotor-shaft relative to the stator, which increases the distance between the magnets and windings - how it does this is (1) black magic to me, (2) based on the voltage downstream of the regulator and (3) something to do with electro-magnets
c. this change in distance leaves the windings in a weaker part of the magnetic field, which in turn reduces the current induced in the windings: a drop in amps for the same resistance results in a decreased voltage (edit: got my wires crossed a couple of times... seems i left my maths brain behind at 30 deg c), because our mate ohm said so
... so if any part of that closed loop is fucked, then the voltage could be out of whack causing the alternator to overcharge the battery
long story short, if you have a fridge-freezer and you have an shonky alternator punching out too many volts, you could fill your fridge-freezer with bottled water and turn it down fully (coldest setting), thereby presenting a big fat juicy load for all those lovely little slaves to work on :)
as to what you do with the frozen bottles of water, well, i'll leave that to your imagination - but i find it does wonders keeping the beer cold
if you can stomach it, here is a riveting read : http://alternatorparts.com/understan...lternators.htm
ps - talking about carrying spares, i wound up with 2 multimeters in our rig - at 10 bucks a piece you can't go wrong!
