Siemens and AES joint venture Fluence is trying to help US utility Arizona Public Service to get to the bottom of an exploding Lithium Ion battery last week. It was a 2 MW battery installed since 2017 in Phoenix. Local firefighters ended up hospitalized. The battery systems were supplied by AES prior to the partnership being formed. The US battery market is poised for take-off and any potential black marks over safety may prevent this. APS says it has projects to take it to 850 MW of battery storage by 2025. One of the big worries with Lithium Ion is that if anything penetrates the battery exterior it can release all of its energy in a few seconds, which is…