Hello, I am looking to build my first Battery pack which will probably be 12s2p with Samsung INR21700-50S cells.
I have seen that NKON sells active [BMS](https://www.nkon.nl/de/jk-bms-bd6a17s8p.html) at what seem to be affordable price.
I have seen in youtube positive reviews of this BMS, although it is supposed to be used in solar Batteries, so i would assume it is not so small…
what do you think about this? do you have a better solution?
Thanks in advance!
these are Balancer only, so I believe they do not turn off (protect) when single cells get over or under charged. if you plan to charge your pack “through” this, I’d choose a real BMS like the JK BD6A20S. I am using them with my Lipo packs (charging and discharging).
Can also recommend the JK BD6A20S, used a few over the years, active balancing with 600ma current, and quite reliable.
I have been using a JBD BMS in my 2 efoils batteries they are 240A peak 80A countinous with bluetooth and active balance they have been flawless so far. I also used JBD BMS in other packs great products and with bluetooth you can monitor the temperature individual voltages etc…
Little off topic, but I would strongly suggest another cell than 50s in a 2p efoil pack. It will get very hot! The amp specs are a bit optimistic on these 
Use the new 50pl or the p50b in stead. I am using the 50s in a 7p or 8p in my current build an that should work fine.
Im guessing that it is for an assist. But yeah. Wont work with an efoil. Maybe with a kid that’s 30kg on top.
It may be off-topic but it is nevertheless good info for me, thank you!
I want to build an assist, i am a pumpfoiler so my foils are 1700 - 2000 sqcm.
For the battery i want to keep it small and light so that i can practice pumping.
but it has to pack a punch since i will be moving to smaller boards as i progress, I am starting with 150L and i have 40L and 7L to try, we will see if that works…
this video gave me some hope https://youtu.be/mR3mwZXEYKU?t=93 he manages to start with 20L and 1000 sqcm…
So far, i have been looking at Molicel P42A, BAK N21700CGP and INR21700-50S,
what do you think about BAK N21700CGP?
both 50pl are p50b are sold out in NKON…
P42 is definitely a great choice considering it has less voltage sag and can deliver more current. Under high current loads the P42 will have an equal capacity as the 50S. But with currents lower than 10A per parralel group) the 50s will have a bit more capacity. Skip the BAK if you are not using it in a higer parralel count, as it can delivery only a tiny bit of current.
Also…the 50S is sold out too, delivery estimate is end of december 2025.
Regarding BMS i am considering using a power supply and two 6s battery balancer for charging the battery instead of a BMS, what do you think about this approach?
I am thinking about omitting the BMS because of size and also because of the size of most BMS…
Since I have assumed 30A current draw (i hope my setup draws less),I will end up with an autonomy of ~16 min, so i will probably have to build at least two batteries
https://de.aliexpress.com/item/1005007094902980.html?spm=a2g0o.productlist.main.10.191e51caClhk9n&algo_pvid=9d83111a-e979-4de4-a9c1-51217075a8c5&algo_exp_id=9d83111a-e979-4de4-a9c1-51217075a8c5-9&pdp_ext_f={"order"%3A"22"%2C"eval"%3A"1"%2C"fromPage"%3A"search"}&pdp_npi=6%40dis!EUR!4.09!2.25!!!4.68!2.57!%40210384b917594828930992105edfaf!12000039386393383!sea!DE!136102093!X!1!0!n_tag%3A-29919%3Bd%3A3d4278b3%3Bm03_new_user%3A-29895&curPageLogUid=XkUn3795VxCz&utparam-url=scene%3Asearch|query_from%3A|x_object_id%3A1005007094902980|_p_origin_prod%3A
Alright, thank you for your answer, then p42b will be, i have seen that most of the other foil assist are using them as well
i just noticed that NKON lists the BAK N21700CGP as 40A batteries while other websites only list them as 18,7A peak 29,5A…
I start with 24lt and 1050 barracuda L, 12s2p 18650 35E. 66kg, it requires good technique and not too choppy/some waves. With barracuda xl is is quite easy and does not use as much power.
2p 50S with a tuned and efficient system would definitely work as an assist if you are not 120kgs
I have been running 10S2P P42 Molicel and also 12S2P P45 Molicel packs for foil assist. Both with AliExpress 6384 and XCross esc.
Can easily get up on 5’5 x 19 46L board on flat water between waves with either pack using foils down to 750cm. I’m 66kg.
Considerably longer run time on P45 12S packs but for pump foiling the P42’s are fine.
I bought some of the BAK 45 cells direct from Shenzen Vapcell - great price but minimum qty of 100 unfortunately! Looking forward to trying them out.
I’d like to try a 12S1P using something like EVE50 for a really lightweight minimal downwind setup.
you got such a great build… at some point i would like to build something like yours…
what do you mean with a tuned and efficient system? have you been trying different pitch propellers or KV motors?
I do weight 95 Kg and my pumping record is around 22s from dockstart, i am hoping that this build allows me to progress quicker and i want to use it as well to get more people hooked up with foil pumping, since i think that the learning curve is too step for the most if you do dockstart and do not have foiling experience.
I will be starting with the standard 6384 140KV and 4.8 folding propeller from Flipsky but i want to give a try at printing props at some point
And finally an on-topic question does your setup have an JK BD6A20S inside?
looking forward for your experience, I would like to try getting batteries directly from china, but for my first build I ruled it out to be too risky.
On top of that i want to keep my build simple so i am looking to get the cells presoldered so i am kind of limited in the cell source…
If i’d build a small foil assist pack now i’d definitely go for one of these new tabless cells. They have lower internal resistance because of the way they are designed. This makes them able to deliver high current without beeing as hot as tabbed (“normal”) cells and will also have lower voltage sag. The Ampace jp40 has had some very good tests, but its “only” 4ah. The EVE 50PL looks really nice!
As example the Ampace jp40 has an internal resistance of 0.004 Ohms (4mΩ) and the Molicel p45b has 0.0135 Ohms (13.5mΩ)
But one word of advice. Don’t use the manufacturers numbers for discharge. Dig a bit on forums and YouTube reviews. Remember that the battery will be in a sealed container with little to no cooling unless you build an aluminium box and connect the cells using thermal pads or something.
