In a message dated 96-05-20 15:18:08 EDT,
fairwind@northernnet.com (Dan Houg) writes:

>.
>
>But a problem remains when the aux battery is heavily discharged and 
>the vehicle is started.  The discharged battery can draw a very heavy 
>current load until battery voltage comes up.  Something in the order 
>of 30, 60, or even 100 amps.  This also has a disadvantage of 
>prodcuing gobs of H2 gas (acutally H2 and O2 in a exquisitely 
>explosive combination) if a conventional deep cycle battery is used.  
>Very heavy battery cables are the order of the day, in addition to a 
>sealed battery box.
>
>Isn't there an electronic device that could limit the charging 
>current in the conductor going to the aux battery?   I can't picture 
>what it would be in my mind but there must be something out there.
>
>It would need to:
>- not interfere with the terminal charging voltage
>
>- be self-adjusting to limit current to say, 30 amps but also let a 
>trickle of 1 or 2 amps thru to top off the battery when it isn't 
>fully discharged.
>
>- be electrically efficient and not create a dangerous amount of 
>heat.

With the alternator regulated to under 14 volts, you will never get much more
than 30 amps going into battery. If the battery is completely dead, it will
not conduct current well until it starts to get some charge on it. #8 wire is
more than suffecient to charge battery and feed the accesories tied to it.
 The wires from the alternator to the original battery are a pair of #12's.
 I've never seen them fry although they do get quite warm with a lot of
accesories, lights, etc being used.

Dennis.