Except Wfcos are hardly known for their longevity, or fast battery chargng performance
Having 3 of them on the shelf, I'm well aware of this. I was just answering the question about the fan running. With the OP just having installed the replacement, the horse is already out of the barn, as the saying goes. With 10 years of service, the OP's WFCO has done perfectly well, longevity-wise. Having had a good experience, there was no compelling reason for the OP to seek out advice. With the fan running in an unusual way (to him), he sought out advice.