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I am making a prototype lithium battery of 2kw / 40 amps.

it's 8p14s, and every bank of 8 parallel is joined with copper sheet in solderless contacts.

I have bought some 0.1mm thick copper sheet and i have measured that it can be maximum 70mm of trace width to carry the current.

It is too thin to carry 2000 Watts even if it's 7cm wide, and very short in length, as it's equivalent to a 1mm wire?

Even if the connections in series are very short, say one inch each, having a 1mm equivalent copper sheet connecting them is a no-no?

Is this true?

Furthermore, by using copper sheet instead of round wire, the surface area is about 20 times larger, so heat dissipation should be at least twice as fast, so i can use thinner wire?

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  • \$\begingroup\$ 0.1mm by 70mm is 7 square millimeters. and a round wire with a diameter of 1.5mm is also 7 mm2 \$\endgroup\$ – com.prehensible May 8 '15 at 10:31
  • \$\begingroup\$ no sorry it's equivalent to a 1.5mm radius wire, a 3mm diameter wire. that's pretty awesome. i get 0.0001 Ohm per cm for that much copper, and at 40amps, it's 40 * 40 * 0.0001 = 0.16 Watts dissipated by the copper sheet per cm roughly. \$\endgroup\$ – com.prehensible May 8 '15 at 13:07
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    \$\begingroup\$ The more I read your questions, the more concerned I become about your safety. I'll repeat -- they can go up in a ball of flame... they can vent HF gas ... they can explode. If you're going to be working with high current lithium battery applications, you should know what you're doing, and have the right equipment available for each failure mode. \$\endgroup\$ – Scott Seidman May 20 '15 at 13:56
  • \$\begingroup\$ That's why i wanted to put a fuse wire on each one for the prototype. I also will use non reversing thermochromic pigment that changes temperature at 70'C to monitor the end caps, if ever one goes to a high temperature, i will be able to see it pretty fast. \$\endgroup\$ – com.prehensible May 22 '15 at 7:08
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In a series battery setup voltage increases and amperage stays constant.

In a parallel battery setup current increases and voltage stays constant.

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  • \$\begingroup\$ Hi i have reworded my question because i have realized that it is more complex that anticipated. 10AWG wire is ok to carry 40 amps along long distances like 10 meters. However with batteries in series, the batteries are so close, like 2 inches of 10AWG wire, i could even use 20awg wire on it safely because the wires are not long? \$\endgroup\$ – com.prehensible May 8 '15 at 9:33
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I tend to use a wire size calculator, such as this one:

http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

It will teach you the things that matter when selecting the size of cable.

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