I reviewed the 2 hits Battleship values to 2.5 multiplier factor.
It is an approximation but this is easier to use this value if you need to assess between two naval fleet during a live game with no AACalc allowed.
It is based on the very even (almost 50%-50% survival equilibrium ) combat between 1 Destroyer @2 and 1 Cruiser @3 against 1 Battleship, 2 hits @4.
http://calc.axisandallies.org/?mustland=0&abortratio=0&saveunits=0&strafeunits=0&aInf=&aArt=&aArm=&aFig=&aBom=&aTra=&aSub=&aDes=&aCru=&aCar=&aBat=1&adBat=&dInf=&dArt=&dArm=&dFig=&dBom=&dTra=&dSub=&dDes=1&dCru=1&dCar=&dBat=&ddBat=&ool_att=Bat-Inf-Art-AArt-Arm-Sub-SSub-Des-Fig-JFig-Cru-Bom-HBom-Car-dBat-Tra&ool_def=Bat-Inf-Art-AArt-Arm-Bom-HBom-Sub-SSub-Des-Car-Cru-Fig-JFig-dBat-Tra&battle=Run&rounds=&reps=10000&luck=pure&ruleset=AA1942&territory=&round=1&pbem=
1 Destroyer @2 and 1 Cruiser @3
5 pips * 2 hits = 10 pips*hits
1 Battleship, 2 hits @4.
4 pips * 1 BB worth 2.5 hits = 10 pips*hits