The red wires come from each series going to a balancing connector for balance charge. 
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The wires go to the round connector. (Dis-) Assembling is easier with the Molex connectors.
This BMS is used for balancing and limiting the upper voltage when charging.
Cells: 21700 & 20700 - Li-ion - Rechargeable batteries: 4000mAh - 5900mAh, 40A - 70A and In Stock | NKON
Copper busbar (2 x 20 x 250 mm): 1 Stück Kupferstreifen T2 Kupfer reiner flacher Stahlstreifen reines Kupfer & Galvanik DIY Materialstärke 1/1,5/2/3/4/5/6/8 mm - AliExpress 1420
Balancer connector: SP28 IP68 Zurück Mutter wasserdichten stecker 2/3/4/5/6/7/9/10/12/14/16/19/22/24/26 Pin steckdose Elektrische kabel Luftfahrt anschlüsse - AliExpress 13
Nickel(-Steel) strips: 1 Rolle 10m 2p vernickeltes Stahlband für 0.15 Lithium-Batterie pack Schweiß band Nickel band Nickelst reifen 2p 23,4*32 * mm - AliExpress 1420
Insulation paper and tape: 1/3/5 m 18650 Batterie-Isolierdichtung, Gerstenpapier, Li-Ionen-Pack, Zellklebstoff, Kleber, Fischband, Wickelektrode, isolierte Pads - AliExpress 13, Hochtemperatur-Wärme-BGA-Band, Wärmedämmband, Polyimid-Klebstoff, isolierendes Klebeband, 3D-Drucktafel-Schutz - AliExpress 13
Molex connectors: https://www.te.com/en/product-1-794617-6.html
Copper and cell holders are cut by myself with my CNC router.
Copper (0.15 x 200 x 1000 mm): Amazon.de
PE-HD (cell holders): Amazon.de
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Cool – what unit do you have?
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Thanks! I wanted to see how the busbar was attached, soldered together…wonder if there’s a better way.
tabless batteries coming which should help with heat. BAK 45D is tabless. will likely see more and more cells with it.
Hi, why not to use 18a charging then, you can charge battery in 40minutes by using two parralel chargers from aliexpress https://aliexpress.ru/item/1005007876857056.html, connected with doides and run generator in field. One cell can be charged 3a (molicel 42b 4.2a in specs), so 10p battery is ok for 36a charge current. Small 3kw inverter generator is ok
That one is to weak even with two, you could take
But even that one alone will not deliver 30A@100V
try 3 in parallel then, but connected with diodes and common ground
I’ve never thought about charging the battery at the field because firstly, after flight it needs to sit for at least one hour, more in warm climate, to lower the temperature. (I’m not sure a 45-47C temp batt should be charged right away.) At least that’s what I’ve read and right on this forum somewhere.
And then after charging, again it is warm and should be let to cool a bit before using it so that it won’t reach sooner it’s temp limit.
Add to this a safe time of charging of two hours to avoid overheating and we have like 4hrs before it can be flown again. Or not?
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