The best place for generator/charging system testing is a generator shop. There are several around my home and all rebuild 6 volt systems.
As for battery testing, same reasoning...goto a battery shop, e.g., Battery Giant, Interstate Batteries. They test with the proper load applied.
When I needed to replace my 6 volt battery (TSC brand), I got a DEKA from Battery Giant. It is significantly heavier than the TSC one.
I use BATTERY TENDERS on all of my batteries that sit for longer than 2 weeks.
The one in my HJ lasted 6 years.