I have a 17 kw Generac branded Carrier. The controller (0H06430) display shows CHECK BATTERY. The terminal board terminals connected to wire 13B and 0 measure 13.4 vdc with tender charger powered and 12.4 vdc with tender charger unpowered. Both look OK to me. Does anyone know what triggers the CHECK BATTERY display? The Owners Manual is silent on this issue.