First build, I have questions and would like to hear any suggestions.

[OffGridForGood]

Actually a long time back we had an EE on the form Solarod - he was commenting on this exact set up with 2, 3 4 and 5 packs,
I chatted with him about having (then) six packs with two being only 100Ah while the rest are a mix of 280Ah and 304Ah packs. This later lead to pairing up the two 100Ah packs to act like a "200Ah" pack, ie closer to the others, and paying with where in the stack they are set, and what size wire and what length to get the balance 'closer'. This was a good learning experience for me and my ESS - since the vast difference of 100Ah and 304Ah packs was far from a balance before his input lead me to a much improved set up. - just noting this for interest.

 

[robbob2112]

Actually a long time back we had an EE on the form Solarod - he was commenting on this exact set up with 2, 3 4 and 5 packs,
I chatted with him about having (then) six packs with two being only 100Ah while the rest are a mix of 280Ah and 304Ah packs. This later lead to pairing up the two 100Ah packs to act like a "200Ah" pack, ie closer to the others, and paying with where in the stack they are set, and what size wire and what length to get the balance 'closer'. This was a good learning experience for me and my ESS - since the vast difference of 100Ah and 304Ah packs was far from a balance before his input lead me to a much improved set up. - just noting this for interest.

That was a good read and there were links to the math. I think it should be able to calculate the perfect placement of cables on bus bar for balance. And it seems to me that it should be possible to leave the cables at standard intervals and just adjust the length or size of cables to get the same effect.

For instance, we have always said make cable length to bus bars from batteries to bus bars the same size and length. But by going up one or two sizss cable for the unbalanced battery you could make the resistance the same. Could also do the same by making the cables to the batteries charging to quick a few inches longer to add resistance.

Another thought would be to take varying thickness and length of copper and sister it up to the bus bar. Or make an oversized bus bar and file a bit out of the sides of make cuts like they do to calibrate current shunts.

Takes a mico-ohm meter to measure the cable connection resistance and also the internal battery resistance and reactance. There is a meter for that. The it is just plug into some linear algebra tables. Then plug the results into a chart to figure out the right size and length of cables.

This stuff has been bouncing around my head for a week. Can't wait to get the meter and bus bar materials to test.

But, the conclusion is doing 2 , 3, or 4 batteries are easy to make perfect. So if you have more wire them in groups to balance.

Calculation of parallel string battery currents

Hi, everybody! I'm a retired EE. I didn't want my EE skills to fade away after retirment, so I exercise them when I can. Whenever I see a non-trivial circuit analysis problem on one of various forums I frequent, I challenge myself to solve it. Recently I watched Will's video about current...

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