# DIY Li-Ion Battery pack
**URL:** https://foil.zone/t/diy-li-ion-battery-pack/18653
**Category:** Electronics (ESC, remote, batteries)
**Created:** [July 17, 2023, 7:12pm UTC](https://foil.zone/t/diy-li-ion-battery-pack/18653 "2023-07-17T19:12:43Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@macfly1202](https://foil.zone/u/macfly1202)
#### Post date: [July 17, 2023, 7:12pm UTC](https://foil.zone/t/diy-li-ion-battery-pack/18653/1 "2023-07-17T19:12:43Z")
Hi,
I currently start to build a “foil-assist” powered build for my wingfoiling gear.
In this topic, I share what I done and looking for battery assembly advice.
I choose the 21700 Samsung INR21700-40T (40T3) 4000mAh - 35A ([Samsung INR21700-40T (40T3) 4000mAh - 35A - 21700 & 20700 - Li-ion - Piles rechargeables | NKON](https://www.nkon.nl/fr/samsung-inr21700-40t3-4000mah-50a.html))
I build a total of 12S8P compose of 2 x 6S8P for better waterproof case organization and the possibility to use my trusted SkyRC RC-Charger (I use it for all my Drone and RC planes without any issues and perfect balance)
I design custom organizer for 21700. Probably not the best - I could have done a better job but will improve it over next iteration.
[place for photos]
I choose nickel strip 0.20 x 10mm ([Amazon.fr](https://www.amazon.fr/gp/product/B09KNLS469/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1))
I use this (expensive on [amazon.fr](http://amazon.fr) 150€ but 80€ on aliexpress) welder solder that is absolutely perfect
[https://www.amazon.fr/dp/B0BTHQ46FS?psc=1&ref=ppx\_yo2ov\_dt\_b\_product\_details](https://www.amazon.fr/dp/B0BTHQ46FS?psc=1&ref=ppx_yo2ov_dt_b_product_details)
I have build 2 pack like this one (6s8p)
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### Author:  [@macfly1202](https://foil.zone/u/macfly1202)
#### Post date: [July 17, 2023, 7:13pm UTC](https://foil.zone/t/diy-li-ion-battery-pack/18653/2 "2023-07-17T19:13:22Z")
[another post for Photos and thingiverse link]
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### Author:  [@macfly1202](https://foil.zone/u/macfly1202)
#### Post date: [July 17, 2023, 8:45pm UTC](https://foil.zone/t/diy-li-ion-battery-pack/18653/3 "2023-07-17T20:45:41Z")
I would like some advice for soldering the “drain” battery wire. I plan to use AWG 8 but I am not sur how to solder it. I have the idea to solder AWG 8 on another nickel strip on ‘+’ pole and ‘-’ pole.
AWG 8 will be the same length than 8p (so approximate 18cm).
I have copper strip ([https://fr.aliexpress.com/item/1005004719059885.html?spm=a2g0o.order\_list.order\_list\_main.20.4ba75e5bDjNUL4&gatewayAdapt=glo2fra](https://fr.aliexpress.com/item/1005004719059885.html?spm=a2g0o.order_list.order_list_main.20.4ba75e5bDjNUL4&gatewayAdapt=glo2fra) the 31mm version) I could use to make connection to assembled pack.
Good or bad idea ? Any advice really appreciate. thanks!
red and blue: AWG 8 wire soldered on copper strip (step 1)
yellow: copper strip 0.2mm (2p cut in center - welder spot (step 2)
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### Author:  [@sat\_be](https://foil.zone/u/sat_be)
#### Post date: [July 18, 2023, 5:43am UTC](https://foil.zone/t/diy-li-ion-battery-pack/18653/4 "2023-07-18T05:43:06Z")
See the link below how I built my batteries. Built two, the first one I spotwelded the terminal nickel strips first and soldered afterwards. The method for the 2nd one is better, I first soldered 8 AWG to a nickel strip and then spotwelded it to the cels. Less thermal stress.
> [@Daniels (un)geared inflatable (slowly built)](https://foil.zone/t/daniels-un-geared-inflatable-slowly-built/8069/81):
>
> New battery Pack Buit a new pair of batteries from Samsung 21700 40T. They were available for a good price from nkon. I built them like the first ones, apart from the main wire connection to the nickel strip. This time I soldered them to the nickel before spotwelding. This way the cells do not absorb heat from soldering which could damage them. Tested them once, they work great. Capacity is slightly lower than the molicel p42A pack but that’s justified by the lower price of the cells. …
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### Author:  [@macfly1202](https://foil.zone/u/macfly1202)
#### Post date: [July 18, 2023, 6:11am UTC](https://foil.zone/t/diy-li-ion-battery-pack/18653/5 "2023-07-18T06:11:54Z")
super Daniel ! Your advice is exactly what I have in my head. thanks !
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### Author:  [@macfly1202](https://foil.zone/u/macfly1202)
#### Post date: [July 18, 2023, 10:55am UTC](https://foil.zone/t/diy-li-ion-battery-pack/18653/6 "2023-07-18T10:55:37Z")
Sorry Daniel @sat_be I forgot to ask where did you find thermoretractable film. My last idea was to use laminate I use on my RC plane wings but perhaps your source is better. 🤓
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### Author:  [@sat\_be](https://foil.zone/u/sat_be)
#### Post date: [July 18, 2023, 11:43am UTC](https://foil.zone/t/diy-li-ion-battery-pack/18653/7 "2023-07-18T11:43:23Z")
From Ali, width 230 is good for 6S, 21700 with my spacers:
Just found this amazing item on AliExpress. Check it out! US $0.68 15％ Off | 1 Meter 18650 Lipo Battery PVC Heat Shrink Tube Pack 85mm ~ 400mm Width Insulated Film Wrap lithium Case Cable Sleeve Blue
[https://a.aliexpress.com/\_mPosPEW](https://a.aliexpress.com/_mPosPEW)