Check your 30A charging fuse. It's on a pretty fat red set of wires. If you get the error right away on a charged battery, you may be getting low voltage across that fuse or fuse connector. I had an issue where my fuse connector was getting a bad connection heating up, causing melted fuses. Your connection could be so poor, that you may be getting low voltage from it. I had to get a new fuse holder and metal crip-on connectors to fix it. I never got a low voltage alarm from it though, but was melting fuses left and right. Strangely, they would still work all melted.