alternators put out 14.1-14.4 I think across the board for engines doing 12V DC. at your reading 13.x you are not charging your batts if running. take a reading at the engine first, then at each step(switch, and batteries themselves). unclear where you took your readings from. if you have an old style Perko batt switch, you charge 1 or 2 or BOTH(not great idea). Process of Elimination. Do checks running, and at rest. You will see a small drop from engine to batt due to resistance but not that large. the veradoclub.com has good public docs on this stuff, since verados are juice hungry
. but it all stands the same across engines inboard/outboard they all run 12V DC. same fer cars man.
at rest batt testing which is borrowed from another site:
http://www.veradoclub.com/smf/index.php?topic=59.0
If running you ought to see 14.1-1.4 at engine alt, then to batt switch, then to batt, maybe drop a little.
I just went to a BEP cluster, dual AGM setup and could not be happier-regulation and isolation
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