I do not like batteries. They require charging systems that sometimes give trouble and leave one stranded. Therefore I put a voltmeter on the dash of my GS500f fairing. Good idea! When the meter showed that the battery was not charging, I was able to get home and check things out. At first, I thought it was the regulator/rectifier. However, as I was using my cheapo multi-meter I found a bad connection from the alternator. I like my dash-mounted voltmeter.
You got one of those LED jobs that change colour depending on voltage? They work well.