How Many Ah flow through each Bus Bar?

[featherlite]

How Many Ah flow through each Bus Bar?

The image below generally depicts one of my DIY, 12v batteries, constructed from 3.2v, 280Ah Lifepo4 cells.



If I wanted to make my own cell interconnects out of wire, rather than using bus bars, what would be the Ah number that I should use when using a standard AWG wire size calculator to determine recommended wire size?

For example, am I correct to assume that, with a hypothetical 280Ah load, about 70Ah would flow through each bus bar (i.e., 280/4 = 70 Ah)?

I searched the forum and saw a few posts tangentially talking about the matter, but got lost in a wall of text that confused me.

Thanks for the help.

 

[SamDeleted]

For example, am I correct to assume that, with a hypothetical 280Ah load, about 70Ah would flow through each bus bar (i.e., 280/4 = 70 Ah)?

I think each bus bar would carry the load , so 280amps

 

[hwy17]

All of the amps.

 

[MisterSandals]

Ah number that I should use when using a standard AWG wire size calculator to determine recommended wire size?

Ah is capacity. You should use the BMS amp rating or your expected max load (in amps) to calculate wire size.

 

[featherlite]

The reason I asked was that when I first assembled my pack with wire interconnects, when I applied a 20 amp load, I measured with a DC clamp meter, about 5 amps flowing through each wire.

 

[Bob B]

In a series configuration .... Which is what the bus bars represent in a 4S battery .... Every point in the circuit sees the same current.

If you have 4 batteries connected to a single bus bar, the wire from each battery will carry 1/4 th the total current assuming the wire lengths and size are identical.

You should do a little research on series VS parallel circuits.

 

[Bob B]

The reason I asked was that when I first assembled my pack with wire interconnects, when I applied a 20 amp load, I measured with a DC clamp meter, about 5 amps flowing through each wire.

Must have been some kind of problem with the measurements.

 

[featherlite]

Must have been some kind of problem with the measurements.

You are absolutely correct. However, the problem was me rather than the meter.

You should do a little research on series VS parallel circuits.

No kidding!

This error in thinking has been with me for quite a while. Ever since I built my first battery.
I recall the old saying "you cannot make sense out of non sense".
I never could make sense of how the amps could differ, because the idea is nonsense.
I knew the theory about series vs. parallel circuits, but I was unable to apply that knowledge to the case at hand, because my mind was jaded by the results of the bad "measurement". Sheesh!

Thank you for your patience and for taking the time to set me straight!

 

[SeaGal]

The reason I asked was that when I first assembled my pack with wire interconnects, when I applied a 20 amp load, I measured with a DC clamp meter, about 5 amps flowing through each wire.

Before you throw the DC clamp meter away, do you know for sure that your 20A load was actually drawing 20A?

It could be that the "wire interconnects" you were using were made of thin wire, or there was some poor connection in the circuit that prevented the full 20A being delivered.

 

[featherlite]

do you know for sure that your 20A load was actually drawing 20A?

This morning, I tested the same DC clamp meter against my Victron smart shunt with a 30A charge from my Victron IP22 charger, and the meter is ok.

It could be that the "wire interconnects" you were using were made of thin wire, or there was some poor connection in the circuit

Good points SeaGal.
However, I am pretty sure it was me engaging in operator error . ?

Thanks for your input!

 

[featherlite]

You should use the BMS amp rating or your expected max load (in amps) to calculate wire size.

That is very helpful advice .... thank you!

 

[Bob B]

You are absolutely correct. However, the problem was me rather than the meter.

No kidding!

This error in thinking has been with me for quite a while. Ever since I built my first battery.
I recall the old saying "you cannot make sense out of non sense".
I never could make sense of how the amps could differ, because the idea is nonsense.
I knew the theory about series vs. parallel circuits, but I was unable to apply that knowledge to the case at hand, because my mind was jaded by the results of the bad "measurement". Sheesh!

Thank you for your patience and for taking the time to set me straight!

Don't beat yourself up too bad .... Glad you are making sense of it now.