Inaccurate battery reporting (solar pathlight)

I purchased a solar pathlight a while back. During fall and winter I don't get direct sunshine on the solar pathlights, but it gets enough drastically slow the battery drain. When I went to go charge it most recently, it was around 50% and after 2 to 3 minutes the device said it was at 100% ... I knew this was inaccurate. I have held the device reset button, removed it from my account and re-added it. But nothing seems to resolve this bug. What options do I have? I no longer have a receipt from purchasing this solar pathlight. To walk into a store and do a 1-for-1 swap.