Yes seems good ones are 100A continuous, 150-200A peak, which is doable… doing more searching…
Thanks Hiorth!
I still have 400x 18650 cells on offer. https://www.li-ion.hu/de/LiFePO4-IFR-18650-32-V-1400mAh-Batterie-Zelle They are connected as a 12v pack right now. These can handle many thousand cycles apparently.
Looks like we have our solution for ion, waterproof battery packs!
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Hi,
Here is my approach for the Battery.
I used 18650 cells to build 2 12s4p packs.
The cells are Samsung 25 R (Samsung INR18650 25R) with maximum discharge current of 20A continuous → this means the battery can deliver 80A continuous (and I have 2 Batteries in parallel so 160A). Max discharge off 400A for 1 second per Battery.
One is done by now, the other I still have to assemble.
The approach is to make a Battery with a integrated fuse. Without welding or battery/Cell soldering.
The connecting wire should have a proper cross section (not like the standard nickel stripes) to reduce heat generation.
I was inspired by the battery holders from Thingivers and designed my own holders with 6 Cells, connectable in a diagonal pattern.
For the connection I used woven copper wire normally used for ground cables.
The Terminals are screwable (M6), and a fuse is integrated.
I soldered only the balancing cables to the woven coper wire.
For the next battery I thing about plating the coper with silver to prevent corrosion and improve lifetime.
Here are the CAD Files and some pictures of the assembly. Hope this will inspire somebody or be helpful:
Copperwire: Amazon.de
http://a360.co/2CB8UMJ
Password: Efoil
best,
Alexander
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@Alexander this looks like a super easy way to DIY build battery packs, not requiring Welding equipment. Have you tested these packs yet? What are you thoughts on durability of packs made this way?
I saw a few guys using a Lipo as a welder.
Nice holders! What material are you using to print it?
wow thats a lot of material just to hold the batteries. Seems like it would not only be cheaper, but also more efficient to use a spot welder with thick nickel strips.
The copper strip likes to oxidize. Especially in the humid environment. The contact between the copper band and cells may not be permanent?
Hi @g.gregory8
Thank you, yes it is, but it’s some work to assemble without creating a short circuit 
I’ll start testing next week. It is not that easy to find a good 12cell charger. the cheaper way would be to build 2 6 S packs to use cheap chargers, balancers etc. I’ll report if I recognize something unusual.
@edivory I used PETG - its elastic and worked for the purpose.
Corrosion: Yes, I thought the same. there are 2 options for this problem: you can order the same woven copper wire with tin plating → no corrosion (typically you have a nickel barrier layer on copper and then tin, otherwise you’ll get copper whisker) but the minimum order was 25 meter for the tin plated version. I don’t need so much.
The other option is to plate it with silver by myself. this is what I’m planing to do for the next pack. You can by silver electrolyte on amazon and plate it with low voltages or even without electricity.
amazon: https://www.amazon.de/Silbergel-50-Alternative-Silber-Elektrolyt-versilbern/dp/B00XPRSN8Q
https://www.amazon.de/Silberelektrolyt-250-versilbern-Versilberung-Galvanik/dp/B01ALCOM0A/ref=sr_1_6?ie=UTF8&qid=1515531577&sr=8-6&keywords=silber+elektrolyt
You know that PETG is very brittle at impacts or quick sudden deformation? It is elastic and giving only if deformation is slow and gentle. Hit it with a hammer and it shatters like glass spitting debris all around. I made some plastic parts for motorcycle and some cracked off at potholes just supporting own weight. Have you tried Nylon?
My 16AH 10C Hobbyking has become a bit swollen (although I thougt that I did treat them nice).
They are and have always been very even on the celll voltage but I suppose they need to be replaced.
I would like your opinion about this battery 27AH pack.
It can deliver 50A continous and 150A peak using LG 3,4AH cells.
Did anybody find anything better or cheaper?
https://www.aliexpress.com/item/Free-Shipping-Battery-48v-27ah-1800W-for-LG-18650-Lithium-Battery-48v-with-2A-Charger-50A/32809337477.html?ws_ab_test=searchweb0_0,searchweb201602_5_10152_10151_10065_10344_10068_10342_10343_10059_10340_10314_10341_10534_100031_10084_10604_10083_10103_10307_10615_10301_10303_10142,searchweb201603_2,ppcSwitch_5_ppcChannel&algo_expid=0be1b33b-71ba-4240-b51a-db737d3c2514-1&algo_pvid=0be1b33b-71ba-4240-b51a-db737d3c2514&priceBeautifyAB=3
Got a picture of the batteries?
I’m working with a company in China for Lithium Ions battery packs for efoils. they make custom sizes both packs and waterproof packs. Also, there is another California based company working on pack specifically for efoil for everyone here based on 12S packs and/or 2x 6S packs.
Its best for us all if we can get away from the LIPO for safety, number of recharges, and ease of shipping. I’ll keep you posted as I get more details/specs/photos/and their pricing.
@Jan the 150A peak is fine, but I feel the 50A continuous may be a little low as you will be straining the battery/wiring all the time. Electronics don’t like to be run at their limits. Just my 2 cents.
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What kind of continuous current have you guys been measuring when using your equipment?
I could not find a pack that could handle more amps and I do not like to weld my own.
I am not to keen on Lipos either but a lot better with a BMS though.
Fine, I hope you will find a better solution and I will wait and see what you will find.
My old battery is this one
It has swollen 2-3mm on one side.
I use almost the same type, i use 6 pieces of 16Ah 4S. So i combine them to have 32Ah 12S. Do you remember how that swelling happened?
I use a frame to assemble them, which puts slight pressure on the laminates, so they actually cannot swell in that direction.
I am not sure if its dangerous with coffee bag style. Its a good practice for using large LiFePO4 cells and i have seen this on many electric vehicles to prevent swelling. Actually the clamping system is sold together with the cells.
https://de.wikipedia.org/wiki/Lithium-Eisenphosphat-Akkumulator#/media/File:Hotzenblitz_ThunderSky-LPF60AH.JPG
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Exactly the same type here. I will add some padding to mine to protect from crashes.