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LiIon, LiPo, NiCd & NiMh General General Battery Support


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Old 05-10-2019, 09:54 AM   #1 (permalink)
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Default Lipo wire size logic

I would like to have some help to understand lipo packs sizes.
example Tattu 22000 6s has 6mm2 wire, this wire is rated 60 amps, however the battery can offer 400+ amps. how will it work? its same concept for other lipos with high discharge, example 6s 5000, 75c, still using 6mm wires.
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Old 05-14-2019, 12:01 AM   #2 (permalink)
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Do you know what a circular mil is? Or a seimen?



I use a standard of 250 Circular Mil / amp when building lipo. designing for a continious discharge, all drained at 10C. Six min. This is pushing the "traditional" limits of (700) circular mil / amp .. ( 700 being generally accepted for building bundled wiring runs)...

When I build a lipo rated for 150 amp contin duty I am fine with 2 pc of 10Ga silicone high strand count. This gives me more amps ( >125) without much temperature rise, than a single 8ga. Going 6 ga is not convenient, wires get to big. The silicone is rated for 200 * C. So (2) 10Ga > (1) 8ga...

12ga, 10ga, even 8 ga will get warm > 100A. High strand count helps, the US standard for 8-10-12ga is less than used by Chinese manufacture. I have heard of it as for every "American amp" use 5-10 "Chinese amps"... Lol. Silicone further raises the ampacity... compared to American standards.

Most 5Ah 6s lipos have a 10ga or 12ga lead. The idea being that it will withstand the discharge statistically without damage from heat... They run by a different set of standards as us.

I have shook loose warm connectors in flight. Never de soldered.

The early Thundr power packs would de solder the 12s connections in flight I have read. poorly designed. Underrated contacts.

Pulling >1700a / 40-50ms at a time I can drain my 6s 15 Ah battery in 32 seconds. ( 325 Wh) If I tried to do this continually the cell level connections would fry... they can only handle about 600 amps for the duration I calculated. The small hobby lipos like a 6s 5000 mah would be even smaller connections cell level. I have read of brand new 4s and 6s Panthers frying on the test... but the wires are 10Ga.. . so they still sell because people think they are built good. They are for all propose: very strong packs.

There is a 400+ page thread on lipo testing on RC groups. Wire size is generally a weakness when high power is involved.

Not many calculate circular mil / amp, of siemens / m.

Im pretty sure manufacrurers choos a 10ga wire cause they have alot of it... and rate the pack with whatever sells... 10C to 100C+.

Im building some serious lipo batteries for some EV motorcycles atm. 20-40Kw 60-100Ah 72v. These will absolutely require 6-4-00 or greater ga wire for continuous operation. Most wire size calculators on the web reference the American standard ( safe and wimpy ) .. @ 12v. Jack that up to 72 v and you can get away with some smaller wire for the same application ( less amps) but the second you start pulling high currents (100A - 400A) for a while you risk heat accumulation.

In general it is a bad thing to skimp on main discharge wires. They need to be big, and will be a bottleneck in wiring if not designed for...
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