# What happens when pulling 160A out of a busbar rated at 100A?

I bought a BusBar from Amazon to parallel connect 5 batteries in my cabin. It is rated at a 100A. I will normally never pull anything close to that out of the batteries, but I have a 1800W non-adjustable vacuum, and I am pondering if I should run it off the batteries using an inverter. Due to normal inefficencies of an inverter, that would probably pull 2000W, equivalent to about 160A at 12V, quite a bit more than the rated max.

I am wondering if this will make the metal on the bus bar so hot it will become a fire hazard? Usually I am done vacuuming in 15 minutes. Usually, any rating is done with a bit of overhead, so maybe 100A means it gets to 20 degrees C, while at 200A it becomes quite hot (like 50 degrees C)?

This is how the bus bar looks:

• heat dissipated is power = I^2R; 160 amp is 1.6 times as much, 1.6x1.6 = 2.56 times as hot as it would have been at 100 amp; power dissipated (as heat) is proportional to the square of the current, which is why you always try to run at the highest voltage possible resulting in the least amount of current to get ? amount of power delivered.
– ron
Mar 12, 2020 at 17:48
• however hot is would get @ 100 amp, expect ~2.56 times as hot @ 160amp; figure if that will be a problem; making your own bus bar is not hard, buy some copper plate off amazon.
– ron
Mar 12, 2020 at 17:52
• Is there a reason you're using something like that for battery interconnects to begin with? Is there not a suitable mains-wiring part you can use instead? Mar 12, 2020 at 23:14
• @ThreePhaseEel Not sure what a "suitable mains-wiring part" would look like (not a native English speaker might be the reason), but in any case, the reason for using something like this is to have optimal distribution of load on all parallel connected batteries. It is possible to wire up your batteries to have an optimal distribution without it, but it is more complex than just using this with a single cable from each battery (you need two, obviously). Mar 12, 2020 at 23:31
• @oligofren -- in North America, I'd be using a UL 1953 listed power distribution block rated to accept the various wire sizes involved. These are generally capable of handling quite a bit of current (the smallest PDBs can handle 100A with ease), are not as terribly expensive as they sound, and use builtin setscrew terminations to accept wires of a variety of sizes without the need for ring terminals. Mar 13, 2020 at 0:02

## 2 Answers

What happens is you exceed the rating of your buss bar by 60%. Doing that is not a good idea and you could melt/deform the base of the buss bar. That buss bar would heat up very fast with that much load on it in a very short time. After 15 minutes it would be so hot it would probably start melting the insulation of other wires attached to it. Plus, I'd be cautious of electrical items purchased on Amazon as they tend to be counterfeit items and could lack UL approval. Bottom line, get a higher rated buss bar.

• I agree but the op could increase the ampacity of the buss bar. An easy way that most home owners could do is take a piece of 1/2” copper pipe smash it flat with a hammer, drill holes and add to the existing buss. I have a very large buss for a dc plating tank that I used this method to connect all my stud mount diodes 1/2 are anode base and the other 1/2 are cathode base but the end result is I have 400 amps available at 12v from a 240-12v transformer , backwards to yours but the same same result 12v at high amperage. Mar 12, 2020 at 17:59
• That was the highest rated buss bar I could find online, basically. Mar 12, 2020 at 18:52
• @oligofren I did a few quick searches and found a lot of 200A and 250A busbars. Mar 12, 2020 at 21:59
• @jsotola Good catch .... been a long day..
– JACK
Mar 12, 2020 at 23:20

I can't believe I'm saying this about a thing "bought on Amazon"...

That's a Blue Sea Systems 2307. It's a 150A bus bar, to begin with, so you're only exceeding it by 7%. Further, it's an American company selling into the Marine marketplace, which has a high expectation of quality and an impressive tolerance for price. So I would expect some overbuild on this product. You'll be fine.

## However, you can just make bus bar.

If the metal cross section is large enough, you don't even need to care which metal it is. For instance, I wouldn't squish copper tubing, I'd just use Schedule 80 iron pipe unsquished, and call it good. (or better for corrosion, Sched 40 brass/copper pipe if you can find that, typically as a nipple). Just drill holes and tap them... e.g. 1/4-20 or the ubiquitous 10-32 used throughout electrical for grounding.

• What does "tap them" mean? Mar 13, 2020 at 6:25
• @oligofren If you've ever seen a thread, like a bolt has on it... the part the bolt goes into must have threads cut in it to match. Doing that is called tapping. 1/4-20 and 10-32 are certain thread sizes common in North American power; your busbar uses 1/4-20. Mar 13, 2020 at 6:39
• I must have the virus and a high fever; I visualized Harper saying something good about amazon.
– JACK
Mar 13, 2020 at 13:16