In a sailboat install, I have an Orion Smart 12/12V -18A Isolated with firmware v1.13 charging my starter battery. The alternator and multiplus charge the 400 Ah bank directly (2 SmartLithium 12V/200), and the Orion charges the 100 Ah AGM start battery. The Orion is running in charger mode. The system is working well and charges the start bat at 14.2 v, then floats it at 13.2 v as expected. Engine Shutdown Detection is OFF, so Orion should always be ON. No problem here. Working as expected.
After about 24 to 48 hours in Float, the output float voltage drops from 13.2 to 12.9V and remains there indefinitely. If I restart the Orion it behaves normally again, bulk to absorption and floats to 13.2V until about 48 hours, then drops to 12.9V or maybe just stops the output.
Any ideas what is going on? Should I be running this in Power Supply mode at 13.2V?