I find that the new 510 top that I bought has a spring that has a sharp protruding end that catches on the battery tops. What eventually happened is that it caught and twisted out of shape. Since then I only load the battery from the bottom. The old GG Slim 901 brass top had a spring that ended on an even loop and this was not an issue. Unfortunately, the springs are not interchangeable. I am going to contact COV to see what I can get. Has anyone else had this happen?