Question: Choosing Wire Gauge/ Bus Bar Thickness?

[dwev2020]

Hi Everyone,

I am wondering if there are any guides to choosing wire gauge or bus bar thickness based on the current discharge of a battery pack?

Specifically, I am wondering about the series connections. Should I choose it based on the max continuous discharge current or the pulse discharge current of the entire pack?

In my specific case, I am looking to connect several already made pouch-cell modules in series to form the pack.

I have also heard that it is dependent on how far the connections are away from each other and things like that.

If anyone has a guide or link to this it would be very helpful.

Thanks in advance.

 

[john61ct]

Yes all over the interwebs, DC amps vs heat safety

Blue Sea Circuit Wizard app is good for learning the factors, but applies to high quality insulated stranded tinned marine copper wire and AWG units only

Cross-section square area is the key, learn to convert from AWG to European units

If you size for peak held for Xsec as a top conservative

then use your continuous as the bottom cheapest size, find a reasonable middle ground in between.

Never hurts to round up, when in doubt go as big as is practical.

In the end an infrared gun and temp sensors tell the real story within your specific rig.

 

[DogDipstick]

Yeah research A/kCmil.

Definitely u build the series connects strong enuf to take full SSC for at least 1 sec. Or else one day you might have a ded batt.

I can build a pack with 250Kcmil/A for the discharge leads.... but the pack buss gets at least 500 or 700 KcmIl / A ( potential) in the buss cause you NEVER want heat inthte buss.

If the (cell) tab can take 600A for a time, it can move 2000A+ for a few milliseconds.... if the SSC is higher than te tab or bus... teh connection will fuse... I build the buss to take 800. Even if the working current is less, like 250A. Mistakes happen. People accidently short things. Fuses talke time to blow. You dont want a fried series connection near the cell ever.

For instance, taking advantage of the whole tab: I make the interconnecting buss plates in my lipos 83,620 circular mil. The discharge leads then are 6Ga, with only 26,251 circ mil. It will happily power its Ev that it s installed in ( working current) without getting hot. The 6 Ga can handle 670A for a few seconds ( 10sec) . It will NEVEr see that current in working use ( unless accidentally shorted, or used to run a spot welder, or if you try to stick weld with it.. even then, some time... ) .


Because of this, the pack wont fuse a cell buss even on a 2000+A hit for a second.

People fry good lipos all the time on spot welders, using them as a SSC power source.. those HK hobby lipo interconnects are weak and easy to blow apart.