There is some danger to that as a general suggestion and it should not
be commonly done because of this.

Connecting another battery with heavy wire directly to the alternator
runs the risk that someday that battery will be called on to supply the
majority of the starter motor current! While the new heavy wire could
support this the next wire segment between the alternator and starter
motor was never intended for starting current! It is safer to connect
the new heavy wire from the new battery to the starter post, and then to
beef up the wire from the starter to the alternator to allow better
charging of both batteries. The previously linked to product from
VanCafe fills the role of the beefed up wire from alternator to starter.

Mark

neil n wrote:
> That's useful info.
>
> I can't state this as a fact, but IMO, it seems the OEM aux. battery
> setup was designed for low draw appliances. It works fine for that.
> But. If one plans to install higher draw appliances and/or lots of
> "bells and whistles" (i.e. digital ice cream maker), as per your
> comments and observations, IMO, installing a new (fused?) large gauge
> wire from alternator to new battery(s), is a great start.
>.............
> Neil.
>
> On Sun, Oct 14, 2012 at 8:04 AM, Rocket J Squirrel
> <camping.elliott@gmail.com> wrote:
>
>> I want to describe an issue I found while working on my van. Most will
>> probably not have this problem unless they are running an '83 or '84
>> digijet (1.9) camper van and draw a lot more out of the alternator than
>> a stock van does. But if this fits your situation, it bears inspecting
>> for this potential problem.
>
>
>
>> I found the second problem when poking around in the connector box
>> located in the engine compartment on the firewall forward of the engine
>> on the driver's side.
>>
>> Bentley 97.56 shows a pair of 12-gauge wires coming off the alternator's
>> B+ terminal and going to the plus connection** in that box.
>
>> When I opened the box I saw that the last inch or so of the wire pair
>> had darkened insulation, and the connector used to connect them to the
>> plus connection was nearly black.
>>
>> Clearly the heavy load I'd been placing on the wiring had overheated
>> that connection, increasing its resistance and further reducing the
>> charge voltage on the engine battery.
>>