Conventional advice says never mix battery brands. That guidance is well-founded for series strings, but there’s surprisingly little data on purely parallel configurations.

I built a 12 V, 500 Ah LiFePO₄ battery bank (1S5P) using mixed-brand cells and instrumented it for continuous monitoring over 73+ days, including high-frequency voltage sampling. The goal was to see whether cell-level differences actually manifest over time in a parallel topology.

What the data shows

No progressive voltage divergence across the observation period

Voltage spread remained within ~10–15 mV

Measured Peukert exponent ≈ 1.00

Thermal effects were small relative to instrumentation noise

In practice, the parallel architecture appears to force electrical convergence when interconnect resistance is low. I’ve been referring to this as “architectural immunity” — the idea that topology can dominate cell-level mismatch under specific conditions.

This is not a recommendation to mix batteries casually, and it’s not a safety guarantee. It’s an attempt to replace folklore with measurements and to define the boundary conditions where this does or does not hold.

Everything is public:

Raw CSV data

Analysis scripts

Full PDF report

Replication protocol

Repo: https://github.com/wkcollis1-eng/Lifepo4-Battery-Banks

I’m posting this to invite critique — especially around failure modes, instrumentation limits, or cases where this model would break down (e.g., higher C-rates, aging asymmetry, thermal gradients, different chemistries).

Happy to answer technical questions.