Hello, thank you for your response! Yes, that is exactly the problem. As soon as I put the old battery back in the battery charges perfectly. When I put the new one back in, it will not charge and the lights are flashing. I have three of the same kind of battery and I am having the same problem with each one of them. The brand is Fluerion. Do you have a particular brand you like to use or recommend? Thank you, Ronnie