Do Wire Runs With Lithium Batteries Have to Be the Same?

Question:

Good morning Jeff,

I have a house bank consisting of (4) 300AH LiPoFe batteries split into two locations. (2) are within three feet of positive and negative bus and the other (2) are 5 to 6 feet away. I have 4/0 cables.
Is it better to bring the farther batteries to the bus bars as not too much difference, or loop them. Electrical engineer says its the same, How?

Answer:

Hi William.  This a great question and one we are seeing more of with the increase in adoption of LiFeP04 batteries on boats.  It is highly recommended when lithium batteries are connected into a bank that the common positive and negative bus bars are installed with even length cables from each battery. This is because the internal resistance of a lithium battery is far lower than a traditional flooded lead acid battery and even slight differences in cable lengths may cause individual batteries to charge or discharge at different rates.  

In your example, there should be (4) 5 to 6 foot jumpers for positive and negative from each battery regardless of the distance to the bus bar - or in other words, all jumpers must be the same length as the longest run.

Here is a great video on installing lithium systems - https://www.youtube.com/watch?v=j2FUMzN0lLg

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