Just finished running my parallel solar battery test — success!

I had a similar low voltage problem when I was working with my four 3S LiFePO4 battery packs. Initially, I thougth the main battery management system was faulty since the individual cells tested fine. I had paralleled them into one big bank and nothing showed up on the screen, wich was incredibly frustrating after spending days wiring the groups.

My initial hunch was that I had a broken circuit, but after some reading on large current flow, I realized it wasn't a break but resistance. I was using 4 AWG copper wire for the jump connections between the series groups, and even though the crimps looked perfect, the sheer amount of resistance in those thicker cables was enought to kill the measurable voltage under any load. I swapped all the jumper cables out for 6 AWG versions, which reduced the overall resistance significantly. Once I did that, the voltage settled right where it should be. It wasn't the connection itself that was bad, but the gauge I chose for the runs between the parallel sections.

My experience with linking groups was actually more about the quality of the connections and the fuses than just whether a wire was fully seated. I was running several 12 volt LiFePO4 groups and when I measured the system voltage, it was fluctuating wildly and often reading zero. I spent a long time checking the main bus bars, and they looked clean, but the resistance seemed off.

I realized I had used different gauges of cable for the main run versus the jumper leads between the groups. While all the ends looked shiny, the thinner jump wires were causing a voltage drop across the entire string, effectively starving the multimeter of a consistent signal. It wasn't a break, but a huge point of resistance. I went back and replaced all the internal jumpers with the same thick 10 gauge cable I used for the initial run.

Once that was done, the voltage stayed perfectly steady and stable. It was a weird problem becasue the meter read voltage right at the terminals, but the overall system felt sluggish until the full cross-section of the copper was present everywhere.

I ran into this issue myself when setting up a few larger groups. It wasn't about the wire size or a single break, but the specific connection hardware. I used the cheap bolt terminals initially and got wierd voltage drops when pulling current. Eventually, I switched the whole system over to copper bus bars with heavy-duty spring-loaded connectors instead. That really stabilized the voltage once the load was applied. It makes a huge difference in how much voltage you actually see under pressure.

I totally get the frustration here. My setup was a bit diferent and I struggled with somethig strange. I had wired my groups up and the meter showed a good voltage reading while the system was completly idle. But the second I hooked up even a small load, the voltage reading plummeted almost to zero. I checked all my crimps and terminals because of the previous advice, and they all felt rock solid. It made me wonder if my balancing routine might be affecting the readings, or if there is some setting in the protection circuit that I am missing.