#5 in Automotive battery jumper cables
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Reddit mentions of HerMia 800A Heavy Duty Pure Copper Jumper Cables Boost Clamp Car Battery Charger Clamps (2 PCS)
Sentiment score: 1
Reddit mentions: 1
We found 1 Reddit mentions of HerMia 800A Heavy Duty Pure Copper Jumper Cables Boost Clamp Car Battery Charger Clamps (2 PCS). Here are the top ones.
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2PCS 800 Amp Strong Car Battery Charger Clamps Connector (1 red + 1 black) Size: 4.72*6.0inInput: 12V; Support up to: 100Amp-800Amp CurrentJumper Cables Clamp was made of pure copper (head part) with good electrical conductivity, with insulation handle for convenient use.These are ideal for Battery chargers (Solar panel, electric fence, etc.) or running applications from a car or leisure batteries (camping ,boat, electric fence, etc.)Widely used for various electrical projects, voltage tester, Suitable for All Car and Truck Batteries.
Specs:
| Color | Item 1 |
| Height | 1.77 Inches |
| Length | 7.87 Inches |
| Number of items | 2 |
| Size | Item 1 |
| Width | 7.09 Inches |
What're you asking now? Are you saying that the terminal posts you're connecting the clamps to are corroded? I mean that's not good, it can result in high resistance. But the clamps usually have such high force that if you're clamping them onto any normal terminal post and you give the clamp a good wiggle so the teeth can bite through any crud, you ought to be able to get definitely sub-milliohm connection. You out to be able to get say <100uOhm (0.0001) if you have solid, high quality clamps that have a continuous copper/brass conduction path all the way from the cable to the jaws with no steel in the way.
Also there's a tendency for high resistance connections in really high amperage circuits to "fix themselves". If you have more than about 0.5 V of drop across a connection, the tips of the contacts start to melt, and that'll usually allow the contact to bed together better, and conduct better. That's from Slade's textbook on contacts by the way.
With jumper cables it's really going to be more about the wire gauge, provided that you have good clamps and you wiggle them a little. They sell absolute shit jumper cables if you don't know what you're buying. I mean look at this crap. 8 gauge? 12 feet? Are you kidding? 8 gauge is 0.63mOhm per foot. Total of 24 feet of wire in those cables, so 15 mOhm. That's garbage. At 100A you're dropping 1.5V. At 500A you're dropping 7.5V.
You do have to be a little more clear about the construction of your battery bank and charge source to get a perfectly correct answer. But the short answer is, no: if you have good clamps you ought to be able to do a hundred amps or two with no sweat.
These? Hell no. Copper plated steel? Get bent.
These? Maaaaybe. If they're not lying that they're actually copper. Looks brass plated, which is OK if it's really copper. But pretty thin looking crap, still. Also note how in both of these products only one of the clamp jaws is connected to the wire through copper. The other is on the opposing, steel arm of the clamp and so is completely useless.
Now this is getting warmer (lol well hopefully less warm!). Note the connections to both sides of the clamp, and the clear use of thick copper for the actual jaws. It's a little bit inconvenient to use a Y harness to do that though.
Ahh, now this is getting there for sure. Dual live jaw, and note the braided copper strap connecting the two sides. And brass is harder than copper, and almost as conductive, which is nice.
My favorites are the ones with cast brass jaws and a connecting strap. I would trust those to say 2-300A continuous. But even they don't really live up to their ratings, for continuous duty. I've run them at 600A and had the copper braid turn purple from oxidation/overheating. So always derate something you use for continuous use, when you know that the manufacturers have a tendency to state the best case intermittent use of the product (especially for a jumper where the use is supposed to be intermittent).