Thanks for any help with the following two questions

TWO RELATED QUESTIONS , Please directly answer one of the two directly.

The goal is to disable the entire circuit if the battery failure transfers load above a preset limit defined by the breakers.

Using Only these Assumptions as Given:
DC circuit, positive side only shown on schematic, all negatives connected. Breakers on positive side only
Assume zero resistance
Fixed voltage
All batteries supply all loads evenly
All breakers normally closed
Make no other assumptions about the circuit...thanks!

Scenario I: Given: Only Load 1 is active drawing 14 amps
So: 1 amp draw per battery

Logically the load at "Breaker 4" is 2 amps, Breaker 3 is 11 amps, Breaker 2 is 8 amps, and Breaker 1 is 3 amps

QUESTION ONE: BASED on ONLY the Assumptions, *** What is the load at Breaker 4 and Breaker 3? ***IS THIS Logic CORRECT IN A DC circuit?

If so:

Scenario 2: If on Leg E the 2 batteries deliver zero power for any reason, then the 2 amps is distributed to the other batteries.

So: Measured amperage at Breakers 1, 2, 3, and 4 increase

What I want to do is first break the entire circuit to Load 1 at Breakers 1 and 2 if the demand exceeds a certain level (Say 10 amps) on Leg A and B if a enough battery failures occur.

If ALL loads are Active from Loads 1, 2 and 3, This will have a transferring cascading effect on all the other breakers disabling the entire circuit. Exactly what I want.

So: If all breakers are rated 10 amps, when enough batteries fail to produce an increase in load exceeding the wiring or battery output limits (say 12) Enough failure will trip all breakers.

QUESTION II ** Is my reasoning correct here? **

I simply do not know the behavior of the load on the legs in a DC circuit.

 

Assume zero resistance

If you do, it is impossible to answer sensibly, because it ALL depends on the resistances.

 

View attachment 343859
Thanks for any help with the following two questions

TWO RELATED QUESTIONS , Please directly answer one of the two directly.

The goal is to disable the entire circuit if the battery failure transfers load above a preset limit defined by the breakers.

Using Only these Assumptions as Given:
DC circuit, positive side only shown on schematic, all negatives connected. Breakers on positive side only
Assume zero resistance
Fixed voltage
All batteries supply all loads evenly
All breakers normally closed
Make no other assumptions about the circuit...thanks!

Scenario I: Given: Only Load 1 is active drawing 14 amps
So: 1 amp draw per battery

Logically the load at "Breaker 4" is 2 amps, Breaker 3 is 11 amps, Breaker 2 is 8 amps, and Breaker 1 is 3 amps

QUESTION ONE: BASED on ONLY the Assumptions, *** What is the load at Breaker 4 and Breaker 3? ***IS THIS Logic CORRECT IN A DC circuit?

This looks correct up to this point.

If so:

Scenario 2: If on Leg E the 2 batteries deliver zero power for any reason, then the 2 amps is distributed to the other batteries.

So: Measured amperage at Breakers 1, 2, 3, and 4 increase

Okay...

What I want to do is first break the entire circuit to Load 1 at Breakers 1 and 2 if the demand exceeds a certain level (Say 10 amps) on Leg A and B if a enough battery failures occur.

If ALL loads are Active from Loads 1, 2 and 3, This will have a transferring cascading effect on all the other breakers disabling the entire circuit. Exactly what I want.

So: If all breakers are rated 10 amps, when enough batteries fail to produce an increase in load exceeding the wiring or battery output limits (say 12) Enough failure will trip all breakers.

QUESTION II ** Is my reasoning correct here? **

I simply do not know the behavior of the load on the legs in a DC circuit.

What is it you are being asked to determine in your second scenario?

Your descriptions of things are very confusing. You talk about the demand on Leg B. What does that mean? Leg B feeds two breakers that share the current supplied by the batteries on that leg (and probably not equally). So exactly WHAT is your "certain level" referring to?

 

If you do, it is impossible to answer sensibly, because it ALL depends on the resistances.

I think that's referring to the resistances of the connecting wires.

 

Hi, I had trouble understanding what you are asking so I made a simulation to point you in the right direction. LTspice is free software and all you need to do is download the attached file and click run. Before I try to answer your questions, take a look at the simulation results:




a) "Logically the load at "Breaker 4" is 2 amps, Breaker 3 is 11 amps, Breaker 2 is 8 amps, and Breaker 1 is 3 amps
QUESTION ONE: BASED on ONLY the Assumptions, *** What is the load at Breaker 4 and Breaker 3? ***IS THIS Logic CORRECT IN A DC circuit?"

I don't know what you mean by "load at breaker"... The currents through loads 2 & 3 must each be zero according to Ohm's Law. In LTspice, there is the "load" component which takes a value in amps. The program infers the resistance for the calculation but forces it to sink 14A. This 14A is distributed across the batteries and as you can see above, the current through each breaker adds to 14A at the load. Therefore, load 2 & 3 must be 0A because there is no current leftover.

b) "Scenario 2: If on Leg E the 2 batteries deliver zero power for any reason, then the 2 amps is distributed to the other batteries.

So: Measured amperage at Breakers 1, 2, 3, and 4 increase"

Not necessarily, the new current through each breaker depends on the impedances toward that node. In this case, by removing Leg 3, the only breaker that actually increases in current is B1. This is because the impedance of the network has changed in accordance to Ohm's Law. To get a precise answer of the currents in any given situation, you'll have to perform an analysis on each node. There are tools and formulas to help with this but the point is to show its not a simple answer. Here are the changes when Leg E is removed:

B1) 3 -> 3.5
B2) 11 -> 10.5
B2a) 8 -> 7
B3) 8 -> 7
B3a) 4 -> 2.3
B4) 2 -> 0
B5) 2 -> 0

Given all this, I'm not really sure what you are trying to do with this data. A good way to describe your objective is to write psuedo-code for all the possible cases the circuit might encounter. It can be very simple langauge but makes sense to use IF-THEN-ELSE statements to describe behavior. For example:

IF <condition 1> THEN <statement 1>

IF <condition 2> THEN <statement 2>

IF <condition 1> AND <condition 2> THEN <statement 3>

Defining the algorithm in this way gives everyone a much better idea of what you are trying to achieve and lays a logical foundation for the components required to implement the result. I realize this can be a lot of take in so go over it slowly and don't be afraid to ask questions.

Most of all, I highly recommend LTspice. It's free and extremely valuable for circuit analysis. However, it's important to point out LTspice uses ideal components unless modified so the results are not always reflective of reality. But for circuits like this, you can get pretty far with basic settings.

 

This looks correct up to this point.



Okay...



What is it you are being asked to determine in your second scenario?

Your descriptions of things are very confusing. You talk about the demand on Leg B. What does that mean? Leg B feeds two breakers that share the current supplied by the batteries on that leg (and probably not equally). So exactly WHAT is your "certain level" referring to?

If you do, it is impossible to answer sensibly, because it ALL depends on the resistances.

OK, thanks for trying, need it answered just as it is.

 

Hi, I had trouble understanding what you are asking so I made a simulation to point you in the right direction. LTspice is free software and all you need to do is download the attached file and click run. Before I try to answer your questions, take a look at the simulation results:

View attachment 343865
View attachment 343866

a) "Logically the load at "Breaker 4" is 2 amps, Breaker 3 is 11 amps, Breaker 2 is 8 amps, and Breaker 1 is 3 amps
QUESTION ONE: BASED on ONLY the Assumptions, *** What is the load at Breaker 4 and Breaker 3? ***IS THIS Logic CORRECT IN A DC circuit?"

I don't know what you mean by "load at breaker"... The currents through loads 2 & 3 must each be zero according to Ohm's Law. In LTspice, there is the "load" component which takes a value in amps. The program infers the resistance for the calculation but forces it to sink 14A. This 14A is distributed across the batteries and as you can see above, the current through each breaker adds to 14A at the load. Therefore, load 2 & 3 must be 0A because there is no current leftover.

b) "Scenario 2: If on Leg E the 2 batteries deliver zero power for any reason, then the 2 amps is distributed to the other batteries.

So: Measured amperage at Breakers 1, 2, 3, and 4 increase"

Not necessarily, the new current through each breaker depends on the impedances toward that node. In this case, by removing Leg 3, the only breaker that actually increases in current is B1. This is because the impedance of the network has changed in accordance to Ohm's Law. To get a precise answer of the currents in any given situation, you'll have to perform an analysis on each node. There are tools and formulas to help with this but the point is to show its not a simple answer. Here are the changes when Leg E is removed:

B1) 3 -> 3.5
B2) 11 -> 10.5
B2a) 8 -> 7
B3) 8 -> 7
B3a) 4 -> 2.3
B4) 2 -> 0
B5) 2 -> 0

Given all this, I'm not really sure what you are trying to do with this data. A good way to describe your objective is to write psuedo-code for all the possible cases the circuit might encounter. It can be very simple langauge but makes sense to use IF-THEN-ELSE statements to describe behavior. For example:

IF <condition 1> THEN <statement 1>

IF <condition 2> THEN <statement 2>

IF <condition 1> AND <condition 2> THEN <statement 3>

Defining the algorithm in this way gives everyone a much better idea of what you are trying to achieve and lays a logical foundation for the components required to implement the result. I realize this can be a lot of take in so go over it slowly and don't be afraid to ask questions.

Most of all, I highly recommend LTspice. It's free and extremely valuable for circuit analysis. However, it's important to point out LTspice uses ideal components unless modified so the results are not always reflective of reality. But for circuits like this, you can get pretty far with basic settings.

Hi, I had trouble understanding what you are asking so I made a simulation to point you in the right direction. LTspice is free software and all you need to do is download the attached file and click run. Before I try to answer your questions, take a look at the simulation results:

View attachment 343865
View attachment 343866

a) "Logically the load at "Breaker 4" is 2 amps, Breaker 3 is 11 amps, Breaker 2 is 8 amps, and Breaker 1 is 3 amps
QUESTION ONE: BASED on ONLY the Assumptions, *** What is the load at Breaker 4 and Breaker 3? ***IS THIS Logic CORRECT IN A DC circuit?"

I don't know what you mean by "load at breaker"... The currents through loads 2 & 3 must each be zero according to Ohm's Law. In LTspice, there is the "load" component which takes a value in amps. The program infers the resistance for the calculation but forces it to sink 14A. This 14A is distributed across the batteries and as you can see above, the current through each breaker adds to 14A at the load. Therefore, load 2 & 3 must be 0A because there is no current leftover.

b) "Scenario 2: If on Leg E the 2 batteries deliver zero power for any reason, then the 2 amps is distributed to the other batteries.

So: Measured amperage at Breakers 1, 2, 3, and 4 increase"

Not necessarily, the new current through each breaker depends on the impedances toward that node. In this case, by removing Leg 3, the only breaker that actually increases in current is B1. This is because the impedance of the network has changed in accordance to Ohm's Law. To get a precise answer of the currents in any given situation, you'll have to perform an analysis on each node. There are tools and formulas to help with this but the point is to show its not a simple answer. Here are the changes when Leg E is removed:

B1) 3 -> 3.5
B2) 11 -> 10.5
B2a) 8 -> 7
B3) 8 -> 7
B3a) 4 -> 2.3
B4) 2 -> 0
B5) 2 -> 0

Given all this, I'm not really sure what you are trying to do with this data. A good way to describe your objective is to write psuedo-code for all the possible cases the circuit might encounter. It can be very simple langauge but makes sense to use IF-THEN-ELSE statements to describe behavior. For example:

IF <condition 1> THEN <statement 1>

IF <condition 2> THEN <statement 2>

IF <condition 1> AND <condition 2> THEN <statement 3>

Defining the algorithm in this way gives everyone a much better idea of what you are trying to achieve and lays a logical foundation for the components required to implement the result. I realize this can be a lot of take in so go over it slowly and don't be afraid to ask questions.

Most of all, I highly recommend LTspice. It's free and extremely valuable for circuit analysis. However, it's important to point out LTspice uses ideal components unless modified so the results are not always reflective of reality. But for circuits like this, you can get pretty far with basic settings.

Thanks brother! There are so many ways to interpret words on something like this, lol. This is a super simple thing of defining the principle of what happens in the legs. The goal is not to get a precise calculation about the breaker loads but to simply define whether breaker amperage increases moving from right to left and from what you are showing it does.

The goal is to disable the entire circuit if the battery failure transfers load above a preset limit defined by the breakers. In other words I am interested in obtaining a cascade tripping of all breakers if two or three batteries are disabled and there is a load that exceeds a set point below the wires load limits as I show in the example. A few batteries fail, draw is higher to whatever degree in the other batteries, this draw exceeds 70% of the load capacity of the wire, the breaker is selected at just below this 70% level and the breaker trips. As there will be THREE Loads possible running at the same time I want ALL the breakers to trip if this battery failure ever occurs. Hopefully that makes it clearer.

 

Revised response:

Thanks brother! Ah, on review the problem is I am using the word "load" to describe an actual device, i.e. Load 1, 2 and 3 and ALSO I am using the word load to describe what is happening at the breaker. I have also not defined that this is a power system and I should be say the ampere rating at the breaker and the Loads should be defined as "devices that draw amperage". There are so many ways to interpret words on something like this, lol.

Really this is a super simple thing I have somehow made seem more complicated when all I want is the "electrical principle" of what happens with general ampere readings at each breakers when a device is drawing (Load 1) as I cannot find it on the internet. The goal is not to get a precise calculation about the breaker loads but to simply define whether breaker amperage increases moving from right to left and from what you are showing it does.

The **goal** is to disable the entire circuit if the battery failure transfers load above a preset limit defined by the breakers. In other words I am interested in obtaining a cascade tripping of all breakers if two or three batteries are disabled and there is a load that exceeds a set point below the wires load limits as I show in the example. A few batteries fail, draw is higher to whatever degree in the other batteries, this draw exceeds 70% of the load capacity of the wire on any of the legs, the breaker is selected at just below this 70% level and the breaker trips. As there will be THREE Loads possible running at the same time I want ALL the breakers to trip if this battery failure ever occurs. Hopefully that makes it clearer.

 

This looks correct up to this point.



Okay...



What is it you are being asked to determine in your second scenario?

Your descriptions of things are very confusing. You talk about the demand on Leg B. What does that mean? Leg B feeds two breakers that share the current supplied by the batteries on that leg (and probably not equally). So exactly WHAT is your "certain level" referring to?

Thanks brother! Ah, on review the problem is I am using the word "load" to describe an actual device, i.e. Load 1, 2 and 3 and ALSO I am using the word load to describe what is happening at the breaker. I have also not defined that this is a power system and I should be say the ampere rating at the breaker and the Loads should be defined as "devices that draw amperage". There are so many ways to interpret words on something like this, lol.

Really this is a super simple thing I have somehow made seem more complicated when all I want is the "electrical principle" of what happens with general ampere readings at each breakers when a device is drawing (Load 1) as I cannot find it on the internet. The goal is not to get a precise calculation about the breaker loads but to simply define whether breaker amperage increases moving from right to left and from what you are showing it does.

The **goal** is to disable the entire circuit if the battery failure transfers load above a preset limit defined by the breakers. In other words I am interested in obtaining a cascade tripping of all breakers if two or three batteries are disabled and there is a load that exceeds a set point below the wires load limits as I show in the example. A few batteries fail, draw is higher to whatever degree in the other batteries, this draw exceeds 70% of the load capacity of the wire on any of the legs, the breaker is selected at just below this 70% level and the breaker trips. As there will be THREE Loads possible running at the same time I want ALL the breakers to trip if this battery failure ever occurs. Hopefully that makes it clearer.

 

Thanks brother! Ah, on review the problem is I am using the word "load" to describe an actual device, i.e. Load 1, 2 and 3 and ALSO I am using the word load to describe what is happening at the breaker. I have also not defined that this is a power system and I should be say the ampere rating at the breaker and the Loads should be defined as "devices that draw amperage". There are so many ways to interpret words on something like this, lol.

Really this is a super simple thing I have somehow made seem more complicated when all I want is the "electrical principle" of what happens with general ampere readings at each breakers when a device is drawing (Load 1) as I cannot find it on the internet. The goal is not to get a precise calculation about the breaker loads but to simply define whether breaker amperage increases moving from right to left and from what you are showing it does.

The **goal** is to disable the entire circuit if the battery failure transfers load above a preset limit defined by the breakers. In other words I am interested in obtaining a cascade tripping of all breakers if two or three batteries are disabled and there is a load that exceeds a set point below the wires load limits as I show in the example. A few batteries fail, draw is higher to whatever degree in the other batteries, this draw exceeds 70% of the load capacity of the wire on any of the legs, the breaker is selected at just below this 70% level and the breaker trips. As there will be THREE Loads possible running at the same time I want ALL the breakers to trip if this battery failure ever occurs. Hopefully that makes it clearer.

I think I have an understanding of what you are asking for and I don't think there is a general solution without some kind of active monitoring. I don't have time now, but I can try to craft a scenario using your circuit in which only some of the breakers will trip. But here is the basic idea. Yes, if one battery fails that will result in more current coming from all of the other batteries. Provided the loads remain the same. But that does not mean that the current in each break will increase -- some may go down and others may go up by even more. But the real problem, for what you are trying to do, is that when certain breakers open, they can cause a load to become isolated from the others and if the other loads can be adequately supplied by the batteries that are still feeding them, then those breakers won't open.

 

I think I have an understanding of what you are asking for and I don't think there is a general solution without some kind of active monitoring. I don't have time now, but I can try to craft a scenario using your circuit in which only some of the breakers will trip. But here is the basic idea. Yes, if one battery fails that will result in more current coming from all of the other batteries. Provided the loads remain the same. But that does not mean that the current in each break will increase -- some may go down and others may go up by even more. But the real problem, for what you are trying to do, is that when certain breakers open, they can cause a load to become isolated from the others and if the other loads can be adequately supplied by the batteries that are still feeding them, then those breakers won't open.

Thanks! I think I understand the impedance part now. All the batteries must be in parallel also to equalizing charging/discharging. Attached is a revised schematic. Thanks for the help, I appreciate it!

 

The batteries have a built-in Battery Management System which I am guessing takes care of impedance as it requires a parallel connection to the batteries outside of the Load side. Does that make sense electronically?

 

The batteries have a built-in Battery Management System which I am guessing takes care of impedance as it requires a parallel connection to the batteries outside of the Load side. Does that make sense electronically?

Unfortunately this makes everything a bit more complicated. You started out by saying no other assumptions but a BMS is an active system which means there is additional feedback of some kind affecting the circuit. This could be current limiting or it could be low voltage cutoff or so combination.

Not only that, there are apparently 14 BMS which are effectively wired parallel. How they will interact with batteries at different voltages and themselves makes things even more unpredictable.

It's not that these questions can't be answered but there is method to the madness. A good chunk of the method is observation and analysis which is time consuming and very much a learning process.

A good place to start is the manufacturers documentation, generating a schematic and defining the algorithm (the step by step process). One you have that, folks have something to work with. Good luck.