Could someone recommend a battery setup? I have FR motor and 160amp high end 14S esc.
I would like to build a light battery with the primary goal of wave riding and downwinding rather than distance efoiling. Given the capabilities of the esc and motor, how small of a batter could I go with?
I was thinking Molicel 45A batteries to be able to handle the current draw in a smaller pack. I was also thinking making multiple batteries that could be added in series for easier charging.
With 45A batteries what is the best way to assemble, multiple nickel strips spot welded? Is that even possible at the current rate? Also, are xt90 connectors enough?
Thanks so much for the help and all the great info in here!
Those Molicels are great batteries, but don’t count on them for 45A - that is just if they are cooled.
My guess is around 14s4p would be as small as I’d go, should get around 15-30mins of foiling depending on how efficient you are. Assuming you have a VESC you can also limit max battery amps so you don’t trash the batteries.
For building the best if a wide nickel strip instead of a bunch of small ones. If I didn’t already have the size I got I would have gone wider:
Xt90 is probably OK, but I’d just use a QS8 connector since that is way better.
The voltage drop is 0.5V (lets assume constant)
Multiplied by 30A = 15W
Per 5 min = 4500 J
And there’s still some juice left in batt to keep frying it!
And the cells heat capacity is : 67 grams × 1 J/grams×K = 67 J/K (i found a site that says that the overall specific heat capacity is one, not sure how accurate it is)
So then, a fully isolated batt would INCREASE its temp by = 4500/67 = 67 K !
And thats just the average, some parts will get even hotter… and that wasnt even 45A
So, given the same motor, esc, and number of cells; does increased voltage (higher S) lower esc temp with higher rpm and hotter battery temps. Whereas, increased cells in parallel (higher P) decreases battery temp and motor rpm, but increases esc temp?
@pablo_foil For figuring out how much lost wattage in the battery the best metric is probably the internal resistance which is 15mOhm. P=I^2R: (30A)^215milliOhm = 13.5W Your ballpark was pretty darn close!
@Sarcomere It depends, I’d say if you had a 14s10p vs a 10s14p pack for the same target RPM. With 14s motor current would be lower and the ESC would be cooler, less losses in wires. Battery probably would be cooler since a proportional decrease in current has a I^2*R decrease in power loss, but maybe that would be a wash with a 10s14P battery and lower R.
Maybe missing something, but in general more S is more better
