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Large amperage gap between 2 identical batteries in parallel

Hedges said:
Busbar seems pretty short, but why not put inverter in middle, one battery on either side, for perfect symmetry?
Click to expand...
Nice idea but this would require making 2 new AWG 2/0 cables and forcing at least one of them to make 2 or 3 impossible 90 angles in 3 dimensions. The wires connecting my busbar to my 200A DC breaker are only about 4 inches long. It would be a lot easier for me to do scenario #2 above (meaning inverter on opposite ends and batteries in the middle), assuming there's any actual benefit to making the change.

What is the consensus on how bad the current wiring setup is (shown again below) ? Seems like nobody knows for sure if this wiring order actually matters over the long haul.

ver1.png
 
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kolek said:
Nice idea but this would require making 2 new AWG 2/0 cables and forcing at least one of them to make 2 or 3 impossible 90 angles in 3 dimensions. The wires connecting my busbar to my 200A DC breaker are only about 4 inches long. It would be a lot easier for me to do scenario #2 above (meaning inverter on opposite ends and batteries in the middle), assuming there's any actual benefit to making the change.

What is the consensus on how bad the current wiring setup is (shown again below) ? Seems like nobody knows for sure if this wiring order actually matters over the long haul.

View attachment 227664
Click to expand...


The short answer is the difference is small enough it probably won't matter in the short or longrun except as an annoyance.

I do still like my last idea - a pure copper washer - polished - coated with no-ox-id special - Put it between the lug and the bus bar on the battery performing battery and see if it makes a difference. If there is a difference but not enough do the other side...


Or just drink two pints close your eyes, spin in circles until you are dizzy and ready to puke, then open your eyes and see if you still care. If you do, drink two more pints and see if you care..... repeat until you don't care.
 
robbob2112 said:
The short answer is the difference is small enough it probably won't matter in the short or longrun except as an annoyance.

Or just drink two pints close your eyes, spin in circles until you are dizzy and ready to puke, then open your eyes and see if you still care. If you do, drink two more pints and see if you care..... repeat until you don't care.
Click to expand...
@kolek Here is the correct answer! test this out and let us know the results :p
 
ScropusGobbleBottom said:
Thanks for this. I just purchased one and when it gets here I am going to give my ESS a colonoscopy.
Click to expand...

Been using YR-1030/YR-1035+ for 8 years.

They're GREAT for relative measurements and identifying outliers. If you're expecting absolute accuracy, don't count on measurements worthy of validating the 0.14mΩ specs on cells.
 
sunshine_eggo said:
Been using YR-1030/YR-1035+ for 8 years.

They're GREAT for relative measurements and identifying outliers. If you're expecting absolute accuracy, don't count on measurements worthy of validating the 0.14mΩ specs on cells.
Click to expand...

Yeah, there is that, but if you have 10 connections in the system done the same way and one reads way higher than the other 9 you have a problem.

Or like the suggested use here, if meassuring one battery against the other and then disconnect the wire at the bus bar and meassure the round trip and compare the two batteries it can turn up interesting data.
 
robbob2112 said:
The short answer is the difference is small enough it probably won't matter in the short or longrun except as an annoyance.

I do still like my last idea - a pure copper washer - polished - coated with no-ox-id special - Put it between the lug and the bus bar on the battery performing battery and see if it makes a difference. If there is a difference but not enough do the other side...


Or just drink two pints close your eyes, spin in circles until you are dizzy and ready to puke, then open your eyes and see if you still care. If you do, drink two more pints and see if you care..... repeat until you don't care.
Click to expand...
Almost impossible to polish without reducing contact area. I prefer to wire brush, scotch bright, or 600g paper contact glued to a piece of glass.
I also like making bolt together load connections with carbon conductive paste

 
Hedges said:
Oh ye of such wimpy inverter power!

Some of us have systems which easily exceed max current for any cell or BMS.

Consider my 23kW continuous, 44kW surge. Divide by 42V low battery to get 548A (continuous), 1048A (surge). And that's before applying efficiency or ripple factor.
That's why I don't bother with silly little LiFePO4 banks. I use lead-acid (AGM) with massive CCA.
(now if I only had loads so large, I would actually have a reason to gloat.)
Click to expand...
Sounds like you just need more LFP batteries and BMS's (BMI?) :)
 
Bananaman321 said:
Almost impossible to polish without reducing contact area. I prefer to wire brush, scotch bright, or 600g paper contact glued to a piece of glass.
I also like making bolt together load connections with carbon conductive paste

Click to expand...

I don't know why you think you can't polish a washer made from copper. The ones I have are 20mm x 1mm with either 3/8 or 5/16 holes..

So, pretty stiff and thick.


I have read a variety of things on both sides of using conductive verse non-conductive grease.
 
ThaiTaffy said:
Lapping a washer...never thought of it but would likely give you the best results seems like holding the workpiece would be a pita though.
Click to expand...
Personally I rarely use washers in electrical connections I feel they add resistance to the connection
Just terminals and serrated nuts for me

I do like using the carbon conductive paste on the high load connections though I really makes a difference
Better than 95% of the high voltage load terminations I've made have come with this stuff pre-installed in the barrel of the connector

I use the dielectric grease in AC electrical panels load connections and also outdoor terminations to prevent corrosion in dissimilar metals.

Tech tip make sure your wirenut treminations are pointing upward in damp or outdoor locations so they don't rust out over time you can also squirt some dielectric grease inside of them
 
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Bananaman321 said:
Personally I rarely use washers in electrical connections I feel they add extra impedance to the connection
Just terminals and serrated nuts for me

I do like using the carbon conductive paste on the high load connections though I really makes a difference
Better than 95% of the high voltage load terminations I've made have come with this stuff pre-installed in the barrel of the connector

I use the dielectric grease in AC electrical panels load connections and also outdoor terminations to prevent corrosion in dissimilar metals.

Tech tip make sure your wirenut treminations are pointing upward in damp or outdoor locations so they don't rust out over time you can also squirt some dielectric grease inside of them
Click to expand...
20240711_221134.jpg All of these connectors come with carbon conductive pace pre-installed in them
They are Homac, and Burndy Connectors and are for use with aluminum and copper conductors
 
robbob2112 said:
I don't know why you think you can't polish a washer made from copper. The ones I have are 20mm x 1mm with either 3/8 or 5/16 holes..

So, pretty stiff and thick.


I have read a variety of things on both sides of using conductive verse non-conductive grease.
Click to expand...
I'm not saying you can't Polish washers I'm saying the likelihood of maintaining truness when polishing is very unlikely
Polishing tends to round over corners reducing true-ness and contact surface area

I feel time is better spent checking and true in bus bars and terminal logs

Crimping can sometimes disfigure a terminal lug reducing contact surface area

And with the small terminals on these lithium batteries the light torque is not enough to draw down a disfigured connector or busbar
 
Bananaman321 said:
I'm not saying you can't Polish washers I'm saying the likelihood of maintaining truness when polishing is very unlikely
Polishing tends to round over corners reducing true-ness and contact surface area

I feel time is better spent checking and true in bus bars and terminal logs

Crimping can sometimes disfigure a terminal lug reducing contact surface area

And with the small terminals on these lithium batteries the light torque is not enough to draw down a disfigured connector or busbar
Click to expand...
I thought that no-ox was used for this reason hence why I'm not listening to anyone suggesting dielectric as an alternative despite tests. Two perfect mating surfaces will extrude any dielectric grease but if there pitted warped you want to improve contact area with a conductive compound rather than hinder it with an insulating one.
 
Bananaman321 said:
Personally I rarely use washers in electrical connections I feel they add extra impedance to the connection
Just terminals and serrated nuts for me
Click to expand...
Can a washer add an impedance to a connection? I would have thought only a resistance :unsure:. But it's a long time ago that I studied inductors and the like.
 
I really think this thread has outlived its usefulness, and like most all of my threads, it was probably never useful to begin with. :rolleyes:
 
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