[Richard]

I went to the Magnum manual again, because I did not remember the cautions. The cautions in my manual are really about two lookouts when using End of Charge on Amperage.

One, use a BMK to get a more accurate reading, otherwise the amp reading comes from the charger.
Two, if DC loads come directly off the battery, it could trick the charger into charging too long, since whatever DC loads there are would be subtracted from the Charge End Setting.

Not worried about either, since we are talking about setting the number at 30. Your background drain is 3 to 4 as you noted. And the loss in the battery cables at 30 amps is also minimal.

Now if you are reading another caution, please tell me, since these are the two I found.

I believe that Chuck installed a Sterling battery to battery to work around the fried alternator issue.