eFoil Battery Packs


#1

I just wanted to start a discussion about what sort of power supplies people are using and having success with. I have ordered two 6S 10,000 mAh LiPo batteries for some initial testing. I have also been looking to build up my own pack using 18650 Li ion cells in a 12s16p configuration for longer battery life. This way the whole system will have the option to be run with the LiPo packs and Li Ion packs interchangeably.
All the reading I have done into the 18650 packs seems to be around a lot of DIY ebike batteries, but the issue I’m coming across is the current draw from the ebike packs will be a lot less than what I’m expecting from the foil. Because of the high current demand there aren’t a lot of easily available BMS boards available for a pack with a high peak current draw. I have been thinking about treating the 18650 pack like a LiPo pack and balance charging it each time and not relying on a BMS. Does anyone have any experience with this?


Battery Solutions
#2

you should check out these batteries: https://hobbyking.com/en_us/multistar-high-capacity-6s-20000mah-multi-rotor-lipo-pack.html
they are insanely cheap and have tons of power with 200A continiuos and 400A peak current.
the best price-performance ratio of lithium based batteries i found on the internet, even better than any 18650 cells and more power. the problem is, you need an rc charger but you dont have to care about bms anymore…


#3

Thanks for the info! I did see those when I was initially searching but wasn’t sure about a couple of the negative reviews but it sounds like a bunch of guys are having good success with them. I have also purchased 10 hover board battery packs cheap on eBay that I have harvested the 18650 cells out of them for a really good /cell price. I am planning on making two 6s packs out of them and balance charging them the same way you would with a LiPo battery pack. But for the amount of effort if I need another spare pack for range I’ll probably end up just going with the 20,000 mAh LiPo packs.

https://m.ebay.com/itm/10-LG-36V-4-4AH-BATTERY-PACK-18650-EBIKE-VAPE-POWERWALL-BATTERIES-200-CELLS-BMS-/201916138726?hash=item2f0323c4e6%3Ag%3AnKUAAOSwuspY9YNZ&_trkparms=pageci%3A9aad17d1-b45e-11e7-ade6-74dbd18077de%7Cparentrq%3A31e1df6b15f0a9c0ee761ccefff8bd76%7Ciid%3A7


#4

It seems like you could easily arrange 10 of the BMS protected 18650 packs as 2 series connected sets of 5 packs in parallel for a total capacity of 21hr at 72v and close to 1.5kw. This would be about 10kg plus the waterproof case.

This would be even better cost/capacity compared to the hobby king cells and it seems like it could last allot longer (as in years of service).

Would the 100 amps max be enough?


#5

I initially thought of leaving the packs as is and doing like you had said. But I inspected a couple of them and they seemed to use a number of different BMS boards throughout the packs. Also though some video reviews of these packs it sounds like these were available because they were recalled due to fire risk, and the likely cause was the BMS boards themselves. I didn’t really want to risk trusting the unknown boards and let alone 10 of them. I would like to manage the charging though a smart charger the same way I willl be charging the smaller LiPo packs I have. I was aiming to have a peak current of 200A just to leave some wiggle room for when I am testing the initial setup, the rest of the equipment is going to be rated to 200+A. Also with this pack like you said I am expecting to get a lot of life out of it, I can’t remember the exclact number but these batteries are rated from LG to have a life of over 500 cycles.


#6

Idea to think about. If all of us can agree on a battery pack model standard, maybe 2 types only? We can get bulk orders that are direct to consumer from the factory for volume discounts. Can someone help identify and work with the manufacturers to setup 2-3 approved suppliers and price points? https://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&SearchText=20000mah+lipo+battery has quite a few and would appreciate if someone spoke the language or already has a connection that is trustworthy to use.


#7

I have just paid for 2, 24000mAH 6S Lipo batteries from an Alibaba supplier for total cost of $839AUD (including delivery to Sydney Australia). Will post further details when/if successfully delivered.


#8

I’ve got a reliable contact for LGMJ1 18650’S. I’m using 70 cells to make a 52V 17.5Ah pack. Vruzend sell an awesome product so you can assemble your pack without spot welding.

My guy is in China and ships to me in Hong Kong for around US30. Not sure what it would cost to the USA.

I paid US350 for 100 pieces including shipping and PayPal expenses.


#9

Good info.
Look like they now sell 2 ea for 9,79$ (489$ for 100) so you made a good deal.


#10

keep me updated on this please, I am in nz and looking at similar options on alibaba

Cheers, DavidC


#11

@DavidC I am also interested in a custom battery pack and will be doing some investigation soon. Maybe we can share shipping etc. when it comes to the crunch. Where are you based? I’m Auckland… Cheers, Glenn


#12

Hey Glen, I am also Auckland and will definitely like to keep in touch about possible shared shipping. I have just purchased two 6s 5200mah lipo batteries from hobby king to do testing with! Have a look , hobbyking is having a big sale atm. I got these for 30bucks usd each.


#13

@LIftAss posted in the propellers section about a Dive-X scooter with a variable angle prop, that in itself was pretty cool, but in tracking down more information, I found a cool direction in a brother product to the Cuda, the Piranha.

One of the biggest issues with the use of our devices is the inability to board and airplane with the batteries. Same issue with the DPV’s the solution they have is to use Dewalt power tool battery packs. Apparently they are cleared for airline flight.

https://dive-xtras.com/piranha-p1-dive-scooter-with-new-power-tool-battery/

I realize there is a tradeoff in package density, but the off the shelf nature of loading in lithium cells onto a board deck seems cool.


#14

I like their gear reducer:


#15

I like the belt drives too. With a two stage gearbox a concentric output is possible. Do you have experience in designing belt drives?


#16

I think this is the way to go, DIY battery pack 12s14P. 18650 cells LOTS of power (min 1.2kwh) and high discharge :blush:
here is a sketch of 6s14p will make 5 of these, then connect 2 in series. Planning on
adding BMS but will balance charge and monitor in the beginning.
expecting at least 30min ride with this setup😊
14 parallel gives a tolerable discharge rate :blush:
(11WH per cell *168= 1.848KWh )


#17

12s14p with some dimentions
will probably be 8-10kg


#18

Looks good @Hiorth. Are you going to build yourself or get custom made somewhere?

Are these safe to build yourself? What equipment is required? I.e DIY spot welder or need to buy an expensive one?


#19

I like your design. I use an additional 3d printed cell fixture, because i want an extra safety margin for crashes and rough handling. Will you spot weld your connections?


#20

best of luck on shipping to Auckland ha, let me know if you find a decent price.
the cheapest cells I could find in Auckland where 7.20$ pp.