Max battery power gives you more power and launch mode, but isn't as fast as ludicrous+ mode. Ludicrous+ mode is only enabled when using the easter egg icon, or from holding down the ludicrous button for 5 seconds and getting the light speed animation. You can tell them apart because the ludicrous+ mode enables the battery temperature display on the instrument cluster, and when it gets to optimal temperature (about 52 degrees C) the cluster changes again to display the transparent vehicle showing animations of both motors, and the left side of the cluster shows you the performance information of acceleration, battery power etc.