Very slow build from France


#183

don’t You have enough power?
I designed the building based on your construction (45mm)
I just got a 440 kV TP 40 mm motor + 1: 6 with 14S battery
You recommend giving up or you have reasonable power.
I plan to build a little efoil for my daughter (35 kg)
Thanks


#184

Why do you take 18650 batteries? lipos are cheaper?


#185

For my application ,top speed… This 40mm don’t have enough torque , and i was running 8s which did not help
But a small board and 35kg ,i think it is perfect , espacially if you run 14s


#186

For high capacity building a li ion pack is way cheaper. And more reliable and safe too.


#187

I’m very sorry for your end of season. Do you think these issues are somehow also linked to the ESC short circuit ? Will you buy these connectors again or do you have new connectors in mind ?


#188

Partial load , more amp on the motor , i will put the log file …
I will buy the connector again , and check more often the male connector to make sure there is good contact all around , i used the same on the battery side and no problem because they were not un pluged as often


#189

i want to use 18650 because they are safer, i can build the battery pack the size and the shape i want, you known what you buy with 18650, not exactly with lipo…
18650 have a higher internal resistance and a lower c rating, but what i have seen with my lipo (multistar) is that when i get below 50% of capacity i am not able to take off without “pumping” on the board, but when i fly i can take them to 3,4v
the C rating on my lipo decreases to much with capacity, probably not the same with higher quality brand and a more efficient setup, but i think 18650 can keep the (lower) C rating all the way to the end .
as far as money, it is the same at the end you just need to build a higher capacity pack at the first, but i gain on flying time
that is the way i see it…


#190

I used those also but they can get hot because of their design. The y are huge connectors and would be awesome with lots of surface area for connection but someone got fancy and put made it so most of the current is only going through the ends where the connector is larger as clearly see in that photo. More than half of that connector is not making a connection so its like a 5-6mm connector (undersized for high current) if you ask me.

Check this connector post: Troubleshooting burnt off Seaking ESC

And this post for some great connectors which have been working for some heavy testing of 150-220A without an issue: Troubleshooting burnt off Seaking ESC


#191

I wanted to share my last log (where my plugs soldered) : this is a 7min ride at partial throttle around 80% , the esc didn’t like it and heated to 60°C, i am happy to see that i can fly under 100A at a decent speed on 8s with this small motor size and propeller at 2600rpm
running partial throttle heats up the esc as i suspected (but better for the battery)

there is a big stretch between 80% and 100% throttle, i go from 90A to 140A for only 400rpm, this is what i will work out for 2019 , putting all the data log on paper and choose the right motor


#192

What temperature does the ESC get to at 100% throttle?


#193

most of the time i was at 40-45°c

at the beginning (june 2018) i never went above 40°c but i was spending most of the time in the water, this last time (october 2018) i didn’t get wet for the first 5 min , funny feeling to be dry on the board :wink:

the esc was hot on top and bottom (the first time), but the battery pack didn’t swell much and i was able to get below 3.7v on this multistar with some pumping for take off

if i am right this ride is around: speed 26km/h, torque 6nm, mecanical power 1665w, and 2300w consuming, it drives me crazy to loose so much !

will see… a 56114 sss has 80% more torque


#194

I can tell you, I really hate ESCs. I had nothing but trouble with them. On my eskate, on my rc planes and on the Hydrofoil. I wish there was just one awesome ESC that would not break, blow up or require complicated setups.


#195

a fun calculator to see the effect on amp/torque on a larger motor…

https://www.ecalc.ch/torquecalc.php?neumotors&lang=en

still no inrunner capable of 9nm under 100mm diameter…
the 4415/2y 83kv is nice :wink:


#196

Hi Alexandre good information shared…what data logger are you using


#197

the one in the esc: hifei swordfish 6.1 , not very accurate but it gives a good idea


#198

Use an ebike controller. I’ve been trying to get others to use them, haven’t seen any other builds with them. Space isn’t a problem on a foilboard. There’s a reason why bikers don’t use RC ESCs and the same reasons why we shouldn’t. Why not try it out? They are also way cheaper, $50 buys a decent one.


#199

And what about erpm ? I need 3600rpm for the propeller , with a 6:1 gearbox … So a about 75000 erpm (édit pair of poles …) , it may be a problem with this type of controller


#200

@Dirkdiggler Can you suggest some good suitable (12S) ebike controllers?


#201

Erpm shouldn’t be a problem most will do at least 28k. Depends on what you want to try - sensored or sensorless, high quality or cheap $40. Voltage and amperage are the key. You can run 36v on a direct drive. Like Alexandre you might need 48v to get the right rpm. You can easily do a shunt mod for higher amperage. The huge plus with an ebike controller is current limiting. It won’t catch fire like the RC controllers will.


#202

Ebikes in Germany are 250W max. Are there controllers for 3kW?