A big welcome Hannes. ..As Nikroc says....I'd check the rectifier, especially the condition of the terminals appart from its output. Also, if you have time, I'd fully charge the battery and measure its charged voltage off the bike and then again 2 or preferably 3 or more days later. A healthy battery should still be close to the original voltage value.

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I have a lot of growing up to do. I realized that the other day inside my fort.