Sounds like the same as mine. This issue won't throw up an error code either. Unfortunately mechanics seem to over rely on error codes to solve issues these days. And RCZ's are famous for throwing up error codes that may not be true! Swapping the circuit board will be a good start.
Yeah that's why you need someone that is a true expert with honesty and integrity, not someone that just reads codes and takes them at face value, changes parts and hopes for the best.
Often times, one failing sensor or component can result in other connected components also throwing codes and that is why it's so easy for dodgy mechanics to say 'see, this code says we need to change your entire transmission', meanwhile, the issue was a single sensor etc.
In fact this type of scenario happened with the RCZ I just bought. The previous owner was having this same exact 'Battery charge...' error message pop up, it was listed on the workshop receipt as 'charging system not working at times'.
So of course, the 'expert' mechanics charged $1400 for a new alternator plus parts and labor which DIDN'T fix the issue because I got the same message a few days ago, it may have played a part in why she traded it in. They would rather charge some poor old lady thousands of dollars than do their damn job and properly diagnose the issue, in this case they could have tested the alternator etc.
Either way, sounds like swapping that circuit board you mentioned is the way to go so I've got one on the way, cheers!
