Lead acid golf cart batteries have a self discharge rate. You can't just let them sit for months without recharging. I had an EZGO I converted to lithium and could leave it at the lake for 6 months without losing any voltage. And being 400lbs lighter it was faster and had an increased range.
The cart should have a sticker applied by Club Car before it left the factory with a mfg date and serial number. EZGO TXT's have a sticker on the frame member under the seat and plainly visible when you raise the seat and lift the plastic flap up.
I think you need to dig out your purchase paperwork. If it was a refurbished cart it should say so in the paperwork. I would contact Club Car CS and see what they have to say.
