Has anybody used an external battery inside an Aquatica housing for Sony a7R II. I've never had an issue with battery life while using wide angle lens but recently I started using a Macro lens (90mm) and all the focusing seems to drain the battery quicker. I now that Nauticam sells an external battery, but I'm using a flash trigger therefore I'm unable to use it. The housing seems to have some available spaces. I was looking into this battery BigBlue Power Bank With Built-in Lightning Cable (https://smile.amazon.com/dp/B01NAQQTA9/ref=psdc_7073960011_t3_B01KUVLMPK).
Any experiences or suggestions?