I am in the game still with renewables. So with caution I speak.
YES. Good money to be made.
YES. Warranty / efficiency concerns on batteries are increasing. ( I am the recent recipient of a warranty exchange) Many are now complaining. But many do not have access the information or logging instruments I have.
ALSO at the start of the year I was fortunate to acquire two new additional Pylontech batteries to the existing. Less than 12 months in they are 2.5% down on efficiency. I can assure you the efficiency degradation is NOT linear. Hence the major two Batteries two years in Just replaced. 50% degradation in COULOMB capacity just this year!