Bit of a hypothetical here, have a system currently running 10S2P Molicel P42 with X Cross 160, Flipsky VX3 and AliExpress 120kv 6384 with Foil Drive twin alloy props. I’m using the Camden box and will probably change the motor to Flipsky 6374 140kv once the AliExpress motor craps out. Although so far un waterproofed, simply soaked in Corrosion X 6384 seems to be bulletproof after maybe 100 sessions!
Looking for a little more run time so I’m going to go to either 8S3P or 12S2P with Molicel P45’s. Using AK 5’5 x 19 46L board and I’m light, 65kg. Motor close to board with internal cable in Axis mast - motor centre line approx 150mm below board. I don’t need more grunt than the 8S can provide, it’s heaps to get me going even with 120kv.
So my hypothetical relates to 2P v 3P I guess, simply want the longest useful run time and wondering whether 3P will be best at achieving that. I do love the instant kick and responsiveness of the 10S but would actually prefer being able to keep going right down to lower voltage levels, The Flipsky VX3 handset has three ‘power’ settings and usually I just run it on Medium and that’s still plenty of grunt.
Have no idea what rpm the foil drive props are optimized for, that would seem to be the critical factor in terms of efficiency of the system. My use is chugging along off foil or just semi on foil and then punching to ride either ground swell or wind swell.
Would welcome any theoretical or practical experience discussion. Thanks
Which RPM the motor/prop is optimised for is not really gonna change the efficiency between 8s and 12s
Picture the ESC like a transformer, for a given RPM and associated power it will always give out the same current and voltage to the motor - with higher input voltage that means it needs less duty cycle - resulting in a lower current from the battery.
So if you leave motor and propeller the same, switching from 8s to 12s will change nothing meaningful in terms of efficiency on the motor side.
On the battery side, on a cell-level 8s3p and 12s2p will also behave the same. The 8s pack will have 1.5x the current draw than 12s, but it also has 1.5x cells in parallel. So every cell will see the exact same current in both cases
That leaves the wires to the ESC as well as the nickel strips in-between the cells- these will see more current at 8s than at 12s (1.5x more) which means - with equal wires - 2.25x the losses. However, if your wires are thick enough these losses are negligible
Funny side fact: The biggest contribution to a fuel consumption of the car is the driver: This can influence your milage up to 20% depending on your mood
What I want to say with that: On a 12S setup you will probably be more likely to “floor” it because that’s just fun - causing less range / efficiency
That’s the only difference I can see, so I would pick based on chargers available, space available and 12s2p or 8s3p fitting better depending on the shape or just toss a coin 
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Thanks so much Ludwig, you do so much for the forum! I’m loathe to ask and I did search but couldn’t find the layout you did some time ago for 12S2P in an 8 x 3 format. If it’s something you have readily available and could post it would be much appreciated. My version has one strip taking full current and was planning to double up the nickel at that point. At least the 12S is reducing current.