Your voltages seem to be quite high, I would measure with a hand held multi-meter set to the 20 Volts DC range and see if the displayed voltages matches. If the voltages you are posting match the multi-meter I would call Magnum customer support to discuss.
Normally, topping charge would be 14.4 to 14.5 volts
Normally, float charge would be 13.5 to 13.6 volts
If your voltage was above 14.5 for any length of time, unless you have AGM batteries they may have lost water, get some distilled water and check your battery levels and top off with distilled water as needed. Over volts on AGM may cause them to vent gas and they can be damaged by long term over-voltage, you might have to consult with the AGM battery maker's tech support if you have AGM and they had long term over-voltage.
One possible reason is that Magnum has a user selectable de-sulfate mode that will set the inverter/charger to output 15.1 volts to drive sulfate off the battery plates of Lead-Acid batteries. Should not be used for AGM batteries. Each time you use the de-sulfate mode you need to check water levels on the batteries. It is intended to be used for a few hours at a time at infrequent intervals of 30-60 days apart. It should be covered in your Magnum manual or you can call their technical support line and discuss with them.
Randy - Manhattan, Kansas
2015 Vista 27N
2016 Honda HR-V