Very inconspicuous

This is where the greatest fire risk lurks in PV systems

It's a fact: the fire in the cellar of Steyregg started in an electricity storage unit of the PV system. This would be the first known case of a fire involving a large battery storage system in Upper Austria. 

PV systems are considered to be very safe, but there is an inconspicuous weak point that - when it happens - is usually to blame for fires.