Eos Energy Enterprises surges after BlackRock reveals stake

** Shares of energy storage systems provider Eos Energy Enterprises EOSE.O climb 17.5% to $6.2, hitting a more than eight-week high

** BlackRock BLK.N discloses a 6.5% stake in EOSE, as per a filing late on Thursday

** BLK's stake is worth more than $85 mln, according to Reuters calculations based on EOSE's last closing price of $5.3

** EOSE will report Q2 results after markets close on July 31

** EOSE has 248.6 mln shares outstanding, with a market cap of $1.32 bln as of Thursday's close

** Including sessions' gains, stock up about 28% YTD