Help Battery keeps dying?

Hey guys, not my bike but my mates it's a suzuki gs 500 2009 not sure about it. But he has out 3 different batteries in it and they have all ended up flat fast in just a few days. The last one he rode it daily and it lasted longer so maybe the bike version of an alternater isn't working well?

 

Probably the stator or regulator ,

here are some simple tests if you have a meter

 

Thanks for the help! Got his bike going only to get t-boned in a car park later that night do worry he's alright just the bikes not