Nibblers Second build

EFOIL.builders Builds
#1

Hey Guys,
im starting my second build the next months. I dont have much time to foil atm, but i want to do some things in my workshop :wink: currently im still riding my first build.
I will use a GONG WING FOIL LEMON FSP PRO - Wing board - GONG Galaxy (gong-galaxy.com)
I know its very low volume. But im pretty sure it will work with some practice on getting up.
The other componets are pretty standard. I will go with flipsky ESC and Motor. and 7" FR prop
The ESC will be mounted in an aluminum case directly to the Mast for propper cooling.
The only thing im completly undecided is the battery. Im realy thinking about to build a Lifepo pack with 33140 cells. The other option would be 21700 cells. Im planning to get a 14s (2x 7s) pack.
I know some of you already used Lifepo.
I also dont want to use a BMS in my batteries. I will charged them balanced. The reason behind is that i want them to be galvanically isolated completly if they are not in use. There will be a voltage monitor in my board to controll every single cell. Also with an accoustic noise that says your battery is low.
I will start posting here when all the parts arrived and i started my work.
Maybe you lifepo and BMS guys have some advice for me in the meantime :wink: I would appreciate that

BR
Chris

#2

Li-Ions don’t require a BMS to be always connected. You can charge through a BMS and have just the cells onboard when riding. If you are going with LiFePo, make sure that the current delivery capabilities are good enough. I am building a 14S7P 21700 pack, which is on the dangerous end considering current delivery I think. For 60-70A battery current during takeoff, each will have to deliver almost 10A.

#3

Thanks for your reply. Yeah thats what i have planned. I want to charge them with the built in BMS on my Graupner Duo 80 Plus and then ride them without. I would go for a 10p pack. Think this will be fin regarding the current.
I planned these cells when i use Li-ion
LG INR21700-M50LT 4890mAh - 14.4A - 21700 & 20700 - Li-ion - Wiederaufladbare Batterien | NKON
This will give me 70A continious and 140A peak. I Think this will be finde even for that small board

1 Like
#4

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That’s exactly what I am using. They output 14.4A continuous per cell if the temperature is acceptable. The continuous rating is derated down to about half when the pack heats up.

#5

Thats cool :slight_smile:
I also was thinking about to make a mast battery. With a 220x50x1000 selfmade mast it should be possbile to fit in a 12s10p pack of the LGs. The drag will be at least 3 times higher compared to a gong V2 mast. But the overall drag wont rise that much.
The only thing im affraid of is winding and bending of the mast under load. The battery pack needs to be a little flexible (at least between the single parallel packs. (connection with wire neccesary)

There are a lot of advantages on this
Very good cooling of electronis and battery.
Its plug and play for every board with us box.
And the best thing is I dont need to work with glas fibre and epoxy xD

But also some downsides
you cant switch the battery at the lake
sealing could be hard
less efficient

Please correct me if im missing something.:wink:
thanks in advance

BR
Chris

#6

To be honest I am not super excited about having a mast battery, simply because of the drag and difficulty of construction.

It is quite straightforward to make a waterproof battery and put it inside a waterproof hatch in the board. That way you have two layers of protection. Additionally, the board ideally rarely touches water, so a lot of the drag comes from the mast assy.

However, having the ESC in the mast is something I can get behind. A bit thicker upper section of the mast, and you make cooling super robust.

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#7

You might consider one of these: li-ion 12s-1p 2kwh 11.8kg 14"x6"x4" used EV battery. May be a bit heavier than an 18650 battery, but it’s a really nicely built battery. Not sure about it’s max amperage, but it comes with a 150a fuse. I’m using them in electric law mowers, ebikes, and my efoil build. Still working on the efoil so I guess I can’t say it’s a great efoil battery yet. There’s also lots of other nice used batteries on that website.

#8

Thanks for your replys guys.
I need to build the pack on my own because im very limited regarding space.
I will do some construction work on the mast battery and try to run some comparison simulations regarding drag. I dont think theres a huge difference afterwards. A Lot of the drag will come from the wings .Also the section of the mast beneath the waterline isnt that big.
Also the board arrived. This thing is so small 0o and it only has arround 3.5 kg.

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#9

Batteries arrived today. Should i go 12s or 14s with the flipsky 120kv motor and FR 7"
I was targeting 40kmh.

BR

#10

Hello again.
had some thoughts about the mast battery.
here are some sketches of what im planning to do.

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The battery tube is seald by a plate with a rubber sealing.
This sealing is inside the electronics comparment. So there is a second sealing stage.
also the esc and the other electronics components will get an additional sealing.
Inside the first stage there will be a sensor which shuts down the whole system if there is a leak.

I am planning to use the motor pot as fuslage to compensate the additional drag of the very big mast.
But while riding thers only a small section of the mast beneath the waterline.
Even with the higher drag the ridetime with a 60ah battery should be fine. (starting could be hard)

Regarding the battery:
There will be 12 single packs with 12p These will be connected by wire because i want it to be little flexible because of the mast bending under load. Im affraid of breaking nickelstrips and short circuits.

Things to clarify

  • 200A circuit breaker needs to be accesible from outside
  • on off switch needs to be accesible from outside
  • balancer port and voltage supply for charging needs to be accesible from outside (i wont use a BMS while riding because of the limited space and i also think there could be trouble with it)
  • how to attach the rear wing. (Maybe could a duct take over the task of the rear wing. tbd)

Im also a little affraid of it to be not very reactive on weight shifting because of the big mast and the low center of gravity.

this would be a lot of welding an machining. :wink: when im back at work i will start to work on the models.
Has someone a 3d model of the gong wings? I want to make a comparison cfd simulation regarding the drag

If you are interested please tell me what you are thinking about that. Thanks in advance.

BR
Chris

1 Like
#11

Hey,
I made some 3D models regarding the mast battery. It will be too big and too heavy so i decided to build it the normal way.
The mast with battery will have around 27 to 30 kg. The overall length with electronics compartment is arround 110cm.
At the moment there is nearly no progression on this build because i have no time.
I will post more when the build goes on.

BR