I have a capacitor bank circuit (16 V, 83 F). I got it from AliExpress. I am planning to install it in my car parallel to my car battery (car battery capacity: 12 V, 50 Ah). Could you please suggest what wire size I need to use?
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4\$\begingroup\$ Please don't install this thing. The internal resitance of supercaps is much higher than that of a car battery, which means that it won't do anything at all. \$\endgroup\$– Jonathan S.Commented Feb 24 at 20:39
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\$\begingroup\$ @JonathanS. Are you sure about that? If the photos are representative, the datasheet is available: samwha.com/electric/product/list_pdf1/db.pdf \$\endgroup\$– Tim WilliamsCommented Feb 24 at 22:48
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\$\begingroup\$ @TimWilliams The internal resistance of a car battery (12V 65Ah for example) is typically around 5mOhms. This is needed to crank the engine (which requires hundreds of amps). That PCB with its 6 caps in series has at least 20mOhms, plus the wire and PCB resistance. It's pretty pointless. \$\endgroup\$– Jonathan S.Commented Feb 24 at 23:24
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\$\begingroup\$ @JonathanS. Still enough to crank a car on, and many have demonstrated such. Now, I'm not saying it's not pointless. but it's clearly incorrect to say it "won't do anything at all". More nuanced would be to say: it won't have any meaningful improvement, except for a few edge cases that are better avoided in the first place; for example, a very low battery (where ESR is much higher). Incidentally, they don't give ESR(T) but we can expect it rises significantly at low temp, as electrolytics do, so won't have much improvement on CCA (cold cranking amps). Basically low charge would be it. \$\endgroup\$– Tim WilliamsCommented Feb 24 at 23:35
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\$\begingroup\$ @JonathanS. car lead-acids are notorious for their limited buffering effect between 12v and 16v so the capacitors are not absolutely pointless for e.g. car audio, motorhome or ham radio setups. Having this much powerful car audio to benefit from 83F caps is "an edge case to be avoided in the first place", I pretty much agree. \$\endgroup\$– fraxinusCommented Feb 25 at 10:56
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The manufacturer of the capacitors claims an ESR of 3.1mΩ at DC for each capacitor, so the total ESR of the bank will be at least 20mΩ.
That implies a rather high potential short circuit current (700A at 14V) however the duration would be short due to the limited energy storage. Also the capacitor is rated at only 260A peak, so it has the potential to damage itself.
At even 100A it would discharge in about 10 seconds so it might be able to give your car a bit of a boost under some conditions. I would go with about AWG8 and a 100A fuse.
answered Feb 24 at 21:24