Anyone with expertise in off-grid system, using Outback? Started 2.5 years ago and have never gotten my system perfected. It is great 8 months of the year, and things quickly go downhill Nov - March. Gone through a generator and 32 gel batteries.
As people have noted, you probably draw more Wh/day in winter than you produce.
If you had reduced consumption such that PV brought the batteries to proper absorption voltage and held them there for proper duration, also never discharged below proper minimum voltage, they should have held up for their specified cycle life.
If you used the generator each morning to add enough charge so that PV could finish the job later, that would have given more Wh/day.
Beyond what system can produce, you have to just not consume more electric power. E.g. switch to gas appliances, firewood, or something.
With lead-acid, battery must be fully recharged including extended absorption time.
What happened to the generator?
Two new lithium batteries seem unable to hold a charge. Seeking a consultant.
Meaning you put some number of amp-hours into the lithium batteries, but get much fewer amp-hours out? That would be not holding a charge.
Or, do you mean they don't seem to have much capacity between "full" and "empty"? In which case, it could be an issue with what voltage you charge to, and what voltage you discharge to.
Unlike lead-acid, it is OK with lithium to bump along near empty and not fully recharge. Just need to prevent over-discharge or over-charge. About half full is ideal for long-term, but will have to periodically recharge past the knee for BMS to do balancing.