john61ct said:
So in parallel. With both lead and LFP?
Any battery will eventually become the same voltage if you parallel them.
It doesn't necessarily mean they will be balanced for capacity, as that depends on the SoC curve of the specific cell/chemistry and the voltage they're at. For example, 3.2v on LiFePO4 covers a wide portion of it's capacity, though the exact voltage varies a bit.
You would have to look at the specs from the cell manufacturer for any specific cell, for their SoC curve to see what voltage is equivalent to what state of charge, to see if you could actually balance them capacity-wise at any particular voltage.
> LFP will not self-balance, period.
Except in Parallel, right?
No, it will not self-balance at all. Self-balancing is a mechanism by which cells will alter their own voltage, like the way lead-acid cells decrease their voltage by boiling off electrolyte, or NiXX cells decrease their voltage by heating up significantly.
It *will* become the same votlage across all the paralleled cells, but that's just normal basic electrical circuit behavior, and is not self-balancing.
Also, no 4/6/12V lead here, only single cell 2V units, as is common for large banks in marine & industrial use cases.
So, if one lead cell is at 1.85V, and the other is at 2.05V, hooking them up **in parallel** (nominal 2V) will cause no current to flow?
Of course it will. Any time you parallel two different voltage batteries (or anything else with two different voltages across them), current flows out of the higher voltage into the lower; if the difference is significant and the internal resistance is low enough, and capacity is high enough, you can even get a fire from it.
But if the voltages are nearly equal already, the current flow will be small, and it could take a long time for the cells to become the very same voltage.
And if one LFP cell is at 2.8V, and the other is at 3.3V, hooking them up in **series** (nominal 6.4V) will cause no current to flow?
It can't--there is nowhere for it to flow. Current can only flow from a higher potential to a lower one. If there is no connection between potentials, there can be no current.
You can draw these out on paper and see how they work. If you're not sure, there are places like https://www.allaboutcircuits.com/textbook/ that have great articles to learn the basics of circuits.
So far I believe you're saying (please correct, and of course looking from input from anyone who knows here, not just amberwolf)
No, it's not unknown; if there is no connection from one potential to another, there is no current, so there can be no balancing.
Correct.
1B: 6P lead - YES
2B: 4P LFP - YES
They will equalize voltage. Balance by capacity is different and depends on the SoC curve and voltage they are actually at, as noted earlier in this post.