There are no real pros or cons.
If you decided to power the reciver separately ensure you disconnect the esc’s power wire on the plug as plugging in the esc harness with 2 battery sources will over load and blow the
You do however have less issues with extra battery’s should you choose not to use a twin power method.
Downside is you have to ensure both power systems are equal ( meaning you can’t allow the receivers battery pack to run out or you end up with a fed boat stuck in full throttle at worse case if the reciver dies)
However you also get the continuing function of servos should the esc’s power fail abling at least some drift control.
Honestly tho there is no reason whatsoever to use a 2nd reciver pack as power. You can notice a speed slow down easily when the battery becomes low giving you enough time to return the vessel to dock.
Years ago I used to think on redundancy’s even to a point on some models that I used a failsafe which when the power dropped off I was able to toggle a micro switch to draw power from a secondary battery ( mainly used as ballest)
However this over engineering is more hastle than its worth. Given that most 7.2v battery’s will run a 540 size motor for 20 mins and a 400 size into 40mins, even brushless motors in the 1500-2000kp range would run for 40 mins using a standard nhmi 7.2 pack ( ignore lipos)
That said if your running with a la battery run times are dramatically increased. As an example I am able to run my triple prop grahpner Wiesel on a single 6v LA (3x400 motors) for an hour without slow down, or over 2 hours with a 12v.
After 20-30 mins I’m pretty much bored of running the model for a while and end up swapping to a yacht or something else for a bit on a sail day.
The choice is yours but imo not worth the extra issues that come with.
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