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Three questions starting with Are my LFP batteries "normal"?

Plecoptera

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Mar 23, 2021
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I spent the coin to add four AmpereTime LiFePO 12V100Ah batteries to my RV system. Previously I always used AGM, and never ran a battery bank.

After much reading, including Victron's pub on Wiring Everything, I arranged the four LFPs in a parallel bank after fully charging individually using my Victron charger. Victron says they all charge to 14.2V without problem. For the bank I was careful on cabling, 4AWG, same length, same terminals, what Victron calls a "Halfway" bank of (+ - 1&2), (+ - 3&4), and then (+ 2&4), (- 1&3).

One battery rests at 13.5V (#4)
Two batteries rest at 13.4V (#3 & #2)
One battery rests at 13.38V (#1)

I can hook up the bank to my panels(4 x 100W in series ~ 80V) via a Victron 100 30 MPPT, and watch it all on BlueTooth, and everything works just peachy. I can charge while using an Inverter, just peachy. The bank all rises to 14.2V, before it heads to storage mode. Then, when I disconnect, let the BMS do its thing, I come back to 13.5V, 13.4V, 13.4V, 13.38V.

I have never watched my batteries at anything like this level of detail, so I don't know if variation of ~0.1V is normal or not. It seems like the BMS should eventually get everything to 13.4V, since that would be average, but that is not what I see.

Is this normal?

Question #2

Would I be better off putting my two 13.4V at #1 & #4, and 13.5V and 13.38V at #2 & #3?

Question #3

My cables from my MPPT are + #1, - #4. My cables from my Inverter are + #3, - #2). So I charge first on the outer two batteries, draw first from the inner two batteries. Is this approximately intelligent?
 
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I prefer the Posts or Bus bars wiring solution in the Victron Wiring Unlimited document. In my setup, all battery cables end up at the common bus bars. The charging devices also end up at the common bus bars. All batteries should have equal access to the charge current.
 
The cells may not be totally balanced. Set a float voltage of 14.0v (3.5v/cell) and let them float for 10 hours. This will give some time for balancing dump.

You should load the battery with about 1 amp for a minute after full charging to burn off any surface charge then let sit open circuit for five minutes before checking battery voltage.
 
Ouch.

Now that you mention it, the cable fittings I already have on the battery posts can simply be rearranged to work with the very nice 4 post Marine grade bus bars that Amazon says I will have in a few days. I originally put two cables on each post, one long, one short... to make it easy to balance, charge, and load. It simplifies things so much and so cleanly it's painful. I wanted two sets of two batteries each, that sometimes live together as four, or get separated and moved around as banks of two. When a pair goes travelling they'll just take their bar with them. I have to make a simple AWG2 cable with ring lugs to bridge two 4 post bars. I saw that on the Victron diagrams, but was so intent on what I had been thinking I blew it off.


You are a gentleman and a scholar.
 
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