The instructions on the Xantrex installation manual says that these two wires (yellow & brown) should be twisted to reduce noise interference. Originally, they were not twisted. We thought this may be the cause of incorrect readings on our starter battery charge, but that wasn't it. After twisting the cables, the problem is still there.
We had the starter battery tested, and the battery health came back at 50%. So we started looking for a new starter battery. Our fist choice is Mastervolt, but there is a limited sales network here. We may have to settle for our second choice, a Trojan 31M AGM.