Amazon 250 amp bus bar upgrade

[Rexracer]

So, I bought a pair of 250 amp copper bus bars from Amazon. After hooking the up during my build, I realized (late) that the plate was actually brass. If it was copper, according to the ampacity chart I looked at, and the plate dimensions, it may have been good for 200 amps as it was 2mm x 19mm. Seems the charts are all over th place.
Looked up brass, and apparently it's only good for about 28% of copper for current capacity, so maybe 55 amps. NOT GOOD!

Anyway, the housing is pretty solid, so I ordered a tinned copper bar, 4mm x 20mm x 1000mm for only $38. Also from Amazon. According to the same chart, that should be good for an easy 300 amps. I only need about 150. I drilled some holes and rebuilt the bus. Should work great.

I also ordered some FR4 composite bar that I'm going to play with. Bus bars, fuse holders. Something to play with. May replace all my ANL fuse holders and make a good class T holder if I upgrade my batteries. Fun!

 

[wpns]

Pictures!

Also what Amazon busbar did you get that was brass?

 

[rhino]

"Charts are all over the place" because most don't specify what temperature increase they are allowing the busbar to increase to and what the ambient temperature is. Temperature would matter depending on how much energy you want to waste and how hot the insulator it is mounted to can withstand.

 

[robbob2112]

(4cm x 20cm)/100 = 0.8 sqcm is good to around 154 amps with 30 degree Celsius rise. Still not great... ya gotta look at the chart and temp from a place referencing bus bars at DC the AC rating is close, but most charts don't mention it.

And note - there are different grades of copper. You want copper 110 that is separated electrical...ETP..

The problem with brass is the good stuff works to about 80% of coppers rating. The cheap stuff with more tin in it good to 30% or so. The impossible part is knowing which is which.

Electrical: Busbar - DC Copper Busbar Ampacities

The following tables have been provided by the Alliance for Telecommunications Industry Solutions (ATIS), T1 Committee, and represent ampacities for busbar sizes and arrangements typically found in the telecommunications industry.

www.copper.org

 

[Rexracer]

The bars were 250 amp copper, marine grade Betybedy bars.

Here's the chart I used

Google Image Result for https://www.australwright.com.au/wp-content/uploads/2019/01/Copper-Busbar-Rating.png

Pic of upgraded bar, with original plate

New bars are tinned 110 copper.

 

[Rexracer]

(4cm x 20cm)/100 = 0.8 sqcm is good to around 154 amps with 30 degree Celsius rise. Still not great... ya gotta look at the chart and temp from a place referencing bus bars at DC the AC rating is close, but most charts don't mention it.

And note - there are different grades of copper. You want copper 110 that is separated electrical...ETP..

The problem with brass is the good stuff works to about 80% of coppers rating. The cheap stuff with more tin in it good to 30% or so. The impossible part is knowing which is which.

Electrical: Busbar - DC Copper Busbar Ampacities

The following tables have been provided by the Alliance for Telecommunications Industry Solutions (ATIS), T1 Committee, and represent ampacities for busbar sizes and arrangements typically found in the telecommunications industry.

www.copper.org

That chart is wrong. It shows 1/8" x 1/2" as 80mm2, and 154 amps, but it's actually 40mm2. 80 mm2 (1/8" x 1") reads as 179mm2 and 275 amps, which is more in line with the chart I used. Weird...

 

[robbob2112]

The bars were 250 amp copper, marine grade Betybedy bars.

Here's the chart I used

Google Image Result for https://www.australwright.com.au/wp-content/uploads/2019/01/Copper-Busbar-Rating.png

Pic of upgraded bar, with original plate

New bars are tinned 110 copper.

It shows the bars rating with a 50c temperature rise... starting at 40c operating temp. So the say 304amps in still air and 340amp in moving air... read the top right above the chart.

So 194f ...you might operate at those temps in an industrial situation...but not at a house...

Bad chart or industrial use...

 

[Rexracer]

It shows the bars rating with a 50c temperature rise... starting at 40c operating temp. So the say 304amps in still air and 340amp in moving air... read the top right above the chart.

So 194f ...you might operate at those temps in an industrial situation...but not at a house...

Bad chart or industrial use...

Yes, I saw that. The other chart also starts at 40c ambient, but with a 30c rise. Wouldn't higher temp rise give a lower amp rating? It's not clear to me, but seems to make sense. I can see these temps being realistic in an under the hood setting, and 40c is not uncommon here for any enclosed space in summer. Either way, my 4x20mm copper bars are now well up to the task of a single 100ah 12.8 vdc lifepo4 and a 1k inverter, especially compared to the 2x19mm brass bar I had. This is only for campsite power, so not so critical as most of the systems I see here.

As always, all the help and info is appreciated!

 

[wpns]

30c rise. Wouldn't higher temp rise give a lower amp rating?

It’s allowable rise in the temperature, think of it as how hot you want your busbar to get. The hotter you allow it to get the more current you can pass through it.

 

[dougbert]

I have been running the good bars of good copper, 600 amp load.

Due to new 2nd inverter, I am replacing the 600 amp bars with VIctron 1000 amp Power In (M10 bolts) unit

documenting it in MY BUILD THREAD


summary schematic




also see

 

[robbob2112]

Charts for wire

at 60c your bars carry around 100amps
at 105c your bars carry a touch over 200a

Nobody wants to run bars at 105c


So, connect things, pull your top amperage through them for half an hour and see how hot they get, if you are happy we are all happy. If they get more than warm to the touch get bigger bars.

A little sanity from the artificial idiot -- the math checks... Your copper is between 1awg and 2awg ​

​

Step 1: Calculate Cross-Sectional Area​

For a copper bar with dimensions 4mm × 20mm:

Area=4×20=80 mm^2

Step 2: Convert to Circular Mils​

Since 1 mm² = 1973.5 circular mils:

80×1973.5=157,880 circular mils

Step 3: Find the Nearest AWG​

Looking at standard AWG sizes:

• 2 AWG = 133,100 circular mils
• 1 AWG = 167,800 circular mils

Since 157,880 circular mils falls between 2 AWG and 1 AWG, the closest match is 1 AWG.

Step 4: Determine Ampacity​

Based on NEC Table 310.16, copper conductors with 90°C insulation (THHN/THWN-2):

• 1 AWG = 150A
• 2 AWG = 130A

So the approximate ampacity of your 4mm × 20mm copper bar would be around 140-150A, depending on installation conditions.

 

[Rexracer]

Makes sense, and is sufficient for now. On the plus side, my fr4 just came in, which means any base I make will be more than capable of handling 600 amps plus. Just gotta allow cooling without risking shorts...still thinking on that. A 1 meter nickel plated c110 bar at 20mm x 10mm is $206. My fr4 bars are 1" wide and 1/2" and 1" thick. I figure 1/2" base and machine ( with my handy drill press and circa 1984 Craftsman milling table) the 1" for the top. Should definitely make some nice ANL holders with fire resistant Lexan windows. It's amazing what you can make with basic tools, a drill press and some small end mills and forstner bits.

Any thoughts on silicone lug protectors on bus bar bolts for protection?

Edit: the math is making my brain hurt. Thanks for the info. Lots of years of this stuff it looks like on your end, Robbob. Falling down the rabbit hole of Circular Mills, I was reading that chart wrong, thinking CM was Centimeters. All the info on stranded wire layout. I Don't even want to know what the layout on these 1awg, 270 strand wires is. I am going to put together a couple of 500 amp busses just because. 2" wide fr4, 5mm x 40mm bars, I'm coming up with 395,000 circular mils if my math is right, which should be around 500 amps at 30c rise. Once I'm done, I'll take a picture and put them in a box on a shelf. Maybe I'll use them one day.

I'll probably leave them with 4 main studs, and space for more, plus maybe some smaller (6mm) studs that I'll add down the line if I end up with a system that needs them. Makes sense to build for the hookups I need instead of a generic number that may not work. Would be nice to have a spot on a bus bar to hook up 6 or 8awg wire with a 6mm lug instead of trying to make it work with 8mm or 10mm...or stacking.

 

[wpns]

Any thoughts on silicone lug protectors on bus bar bolts for protection?

I’m 3D printing covers for mine, though it’s an iterative process.

 

[Rexracer]

I’m 3D printing covers for mine, though it’s an iterative process. View attachment 275777

If I only had a 3d printer....

 

[wpns]

If I only had a 3d printer....

Yet another expensive hobby. If you think the solar power world is “give a mouse a cookie“ then you should check out the 3-D printing world.

 

[Rexracer]

Yet another expensive hobby. If you think the solar power world is “give a mouse a cookie“ then you should check out the 3-D printing world.

Yeah, I've had a few. Motorcycle Roadracing was probably the most fun, and definitely the biggest adrenaline pump.

 

[robbob2112]

Edit: the math is making my brain hurt. Thanks for the info. Lots of years of this stuff it looks like on your end, Robbob. Falling down the rabbit hole of Circular Mills, I was reading that chart wrong, thinking CM was Centimeters.

Don't feel bad about that - I did it to at first until I looked at the chart and the numbers looked "wrong"


If you want to make bus bars.... cuts with a metal blade on a chop saw or table saw... then just drill the holes for bolts..or to tap screws to it... nickle plating is easy with an dc supply..you need few amps or less at 10v or so.. instructions are online... you could use a battery with an incandescent light bulb in the circuit to limit current... pure nickle strips are $10 or so

Speedy Metals 1/4" x 4" 110 Copper Flat

Buy 110 Copper Flat from Speedy Metals, America's favorite online metal store with unsurpassed service, highest quality and best selection.

www.speedymetals.com

 

[Rexracer]

Don't feel bad about that - I did it to at first until I looked at the chart and the numbers looked "wrong"


If you want to make bus bars.... cuts with a metal blade on a chop saw or table saw... then just drill the holes for bolts..or to tap screws to it... nickle plating is easy with an dc supply..you need few amps or less at 10v or so.. instructions are online... you could use a battery with an incandescent light bulb in the circuit to limit current... pure nickle strips are $10 or so

Speedy Metals 1/4" x 4" 110 Copper Flat

Buy 110 Copper Flat from Speedy Metals, America's favorite online metal store with unsurpassed service, highest quality and best selection.

www.speedymetals.com

I do really want to try that. Much more choice with unplated copper. Also takes care of holes and cut ends. I'll have to find a good video. I don't have a benchtop power supply, but do have tons of dc power packs from 3- 20+ vdc and .25 to 3-5 amps. I'm sure something would work.

Bought an inexpensive power supply from Amazon. Looks like it works well. Pretty lights, easy to set. Zero output. Send8ng back. Luckily Amazon makes it easy. I'll get my refund tomorrow and try another power supply. Got a Nickel rod and copper bar coming. We'll see how the plating works.