Get a magnet and check the crimped on battery to
alternator or any other crimped on lug type
connector to make sure it's not steel.

Most all aftermarket FLAPS battery cables have
copper plated steel lugs which will rust.

Steel BTW has 50 times less electrical
conductivity than copper.

Rule this out first beforee preoceeding. There is
something that is reducing your output after it
leaves the alternator.

A bad battery can also give you low readings.

Robert

1982 Westfalia

--- Geza Polony <gezapolony@SBCGLOBAL.NET> wrote:

> OK, tests in. There's a voltage drop all along
> the way, but grounds are good.
>
> At Alt, no load 14.15 vdc
> At Alt, loaded 14.03 vdc
> Alt  to ground, same readings
>
> At vehicle battery, across terminals, no load
> 13.73-75 vdc (.42 drop)
> Vehicle battery, across terminals, loaded,
> 12.82-85 vdc (1.21 vdc drop)
> Vehicle battery to ground, no significant
> difference
>
> At aux battery across terminals, no load, 13.17
> vdc (.58 drop from vehicle
> battery, .98 from alt.)
> Aux battery across terminals, loaded, 12.32-39
> vdc (.5 drop from vehicle
> battery, 1.71 from alt.)
> Aux  battery to ground, no difference.
>
>
> The worst problem here is what I suspected, a
> more than 1.5 volt drop
> between alternator under load and aux battery
> under load. The more you load
> it, the worse it gets. (I was using high beams,
> AC, and fridge.)
>
> This is with the stock 23 year-old wiring and
> relays, but upgrades to
> grounds. I doubt if any battery set-up would
> work right given these conditions.
>
> Any idea what an acceptable voltage drop would
> be using new 6 AWG wire and a
> new OEM-type relay? It seems like ideally, you
> could get 13.8vdc at the aux
> battery under load--but how likely is that to
> happen?
>

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