All busbar s not created equal

[fafrd]

I am looking at this amazon bar: https://www.amazon.com/Tocas-Module-Design-Distribution-Terminal/dp/B08Q7QN79M

I like the cover. Bar is made of brass. Is there anything similar made with copper? Or does it matter? Rated 300A and I would rarely exceed 150 amps.

I used a pair of these recently for an off-grid build. Very nice (and high-quality).

 

[Symbioquine]

I went with 0.25"x1.5"x36" oxygen free copper bar stock clamped between pieces of HDPE plastic. I like how thoroughly overkill it is from an ampacity standpoint and that I can drill exactly the holes I need.

 

[Hedges]

I went with 0.25"x1.5"x36" oxygen free copper bar stock clamped between pieces of HDPE plastic. I like how thoroughly overkill it is from an ampacity standpoint and that I can drill exactly the holes I need.

View attachment 70697

Busbars are sufficient, look great.
Can't quite tell what's up with 4 skinny negative wires, 2 fatter positive.
I put my ring terminals on both sides of the busbar rather than stacking.

How well does the Buss MRCB 200A breaker meet current and future needs?
I don't know what voltage or Ah you have.
Check out the specs for the breaker, make sure it can interrupt available fault current.

Series 187 marine rated circuit breaker (MRCB)

<p>The Series 187 Marine Rated Circuit Breaker features a manual reset with switchable function and is single pole thermal type.</p>

www.eaton.com

I would think OK for 12V AGM, marginal for 24V.
Insufficient for lithium.

 

[Symbioquine]

Busbars are sufficient, look great.

TY

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Sorry in advance for any thread derailment going on here...

Busbars are sufficient, look great.
Can't quite tell what's up with 4 skinny negative wires, 2 fatter positive.
I put my ring terminals on both sides of the busbar rather than stacking.

I used two runs of 8 AWG wire for each BMS connection per the max recommendation in the Overkill BMS manual - I would have gone larger, but the lugs I've got would have yielded a substantially worse contact so for now I figured I'd rather have the heat spread out over the length of those cables than focused on a bad connection at my expensive BMS'.

Good call on the stacking, I might split those up in the future or just switch to 2/0 cable for the negatives lines too...

How well does the Buss MRCB 200A breaker meet current and future needs?
I don't know what voltage or Ah you have.
Check out the specs for the breaker, make sure it can interrupt available fault current.

2 x (8s LF280K) with 24v 100A Overkill BMS'.

The Blue Sea folks claim it can interrupt 3000A @ 28v; https://www.bluesea.com/products/7049/187-Series_Circuit_Breaker_-_Panel_Mount_200A I have a 300A ANL fuse I was thinking of putting inline as well, but erred on the side of fewer failure points and complexity.

 

[Hedges]

I've read 100 Ah AGM can deliver 4000W into a short.
For car batteries, I start with cranking amps to compute resistance (8.5V cranking), then calculate current into zero ohs.

I figure a lithium battery can deliver, 20,000A into short circuit. Divide voltage by internal resistance. Add wire resistance, see if it helps. Don't forget to add up parallel batteries.
What do you come up with for your battery, based on its specs?

ANL "IR 2700A" at 80V
Sounds like barely enough for a car battery. Except, don't know how much better at 12V.

Blue Sea says 6000A at 32V, sounds better

ANL Fuse - 300 Amp - Blue Sea Systems

Use with ANL Fuse Blocks for many applications with 35-750 Amp loads

www.bluesea.com

https://www.eaton.com/content/dam/eaton/products/electrical-circuit-protection/fuses/data-sheets/bus-ele-ds-2024-anl.pdf

Class T is rated 20kA interrupting (at 125V)
Midnight has a breaker rated 50kA
Ferraz Shawmut has a fuse rated 50kA
Some other fuses are rated 10kA

 

[Symbioquine]

I figure a lithium battery can deliver, 20,000A into short circuit. Divide voltage by internal resistance. Add wire resistance, see if it helps. Don't forget to add up parallel batteries.
What do you come up with for your battery, based on its specs?

I see what you mean about >20,000A with a dead short circuit.

Taking one of the test report values for my Eve LF280K cells I get;

3.296V / 0.00014Ω = ~23500A

However, that's only if there's a short directly between the terminals of the battery...

Wire resistance ends up being pretty significant though I think. For example every two feet of 2/0 cable provides another 0.00015Ω of resistance so if there were just two feet of 2/0 cable involved in the short circuit that amperage would be approximately halved.

I'd need to measure some cable lengths and do a bit more math, but I wouldn't be surprised if I'd be in the right ballpark for the ANL fuse I've got and maybe even safe with just the Blue Sea breaker.

 

[Hedges]

I see what you mean about >20,000A with a dead short circuit.

Taking one of the test report values for my Eve LF280K cells I get;

3.296V / 0.00014Ω = ~23500A

However, that's only if there's a short directly between the terminals of the battery...

Wire resistance ends up being pretty significant though I think. For example every two feet of 2/0 cable provides another 0.00015Ω of resistance so if there were just two feet of 2/0 cable involved in the short circuit that amperage would be approximately halved.

If you're running your inverter on 2.296V

 

[jwelter99]

I see what you mean about >20,000A with a dead short circuit.

Taking one of the test report values for my Eve LF280K cells I get;

3.296V / 0.00014Ω = ~23500A

However, that's only if there's a short directly between the terminals of the battery...

Wire resistance ends up being pretty significant though I think. For example every two feet of 2/0 cable provides another 0.00015Ω of resistance so if there were just two feet of 2/0 cable involved in the short circuit that amperage would be approximately halved.

I'd need to measure some cable lengths and do a bit more math, but I wouldn't be surprised if I'd be in the right ballpark for the ANL fuse I've got and maybe even safe with just the Blue Sea breaker.

This is a good application for a ~125A MRBF fuse right on the positive battery terminal of each of your 8S packs. These will protect everything downstream as close to the "source" as possible.

MRBF have a reasonably high AIC - not as good as Class-T - but at 32V they are rated to 5000VA, and at 14V 10000VA.

I would not use that Eaton breaker to be your only protection device. It is too far away from the batteries and not a high enough AIC rating.

MRBF Terminal Fuse Block - 30 to 300A - Blue Sea Systems

Easily and economically satisfies ABYC 7 circuit protection rule by mounting on a 3/8 battery post, battery switch or bus bar.

www.bluesea.com