** EV maker Rivian's RIVN.O shares fall 7.6% to $18.62 premarket

** On Monday, co launched offer to sell 75 mln shares; to raise $1.5 bln based on last close of $20.14

** RIVN plans to use proceeds to fund equity contributions as part of a loan agreement with the U.S. Department of Energy

** Forecast Q2 revenue between $1.55 bln and $1.65 bln, vs. analysts' avg. estimate of $1.45 bln - data compiled by LSEG

** Estimated $5.3 bln in cash and cash equivalents at the end of June, up from $4.8 bln at the end of Q1

** Up to last close, stock has risen 2.2% YTD