Also have a look at
@Dellmassive 's' How I done it 'threads, especially
Battery Monitoring -- How I Done It -- Part #1 Battery monitoring is a very important part of your 12v system . . . . whether its just the vans starter battery or your leisure setup keeping an eye on the power in your battery bank will keep you from breaking down and make sure your weekends...
www.t6forum.com
I have the Bluetooth BM2 and a USB voltmeter in an extension from the 12v sat on the dash that I can see through the window.
A low starter battery charge could be caused by several factors, including battery age, a faulty alternator, or a parasitic draw. First, check the battery’s age most batteries last 4–6 years. Then, test the charging voltage while the engine is running; it should be around 13.8V–14.4V. If it’s lower, the alternator may be failing.
But yes, if you want to know more, then you can visit:
Filemail Administration Account - t6forum.com