I have the MPPT 100/30 feeding my 2 6V flooded wet lead acid batteries with a Magnum 1012 inverter. The system worked fine for 18 months and now this winter I'm not getting complete charge in days that it was charging to 100%. The system is in a cabin with infrequent use and temperatures are around 0-4C.
Day one: drew the batteries from 85%-69% and the next day they only recovered to 74% in full sun with 11.64V min. 13.59V max. 69% min.- 78% max. charge .....(Yield 770Wh, 244W, 43.51V)
Day two: drew the batteries from 78%-59% and the next day they only recovered to 74% in full sun with 11.55V. min. to 13.64Vmax. 59% min. to 70% max. charge..... (Yield 1.00kWh, 263W, 42.05V )
Day three: drew the batteries from 70%-54% we left that day with the batteries at 54%
With this trend the system will fail if we are there for a week and it does not closer to 100% recovery in a full sun day.
What do I check?
Why the change?