ΔV
Cell voltage spread
The voltage gap between the highest and lowest cell in the pack. A healthy pack stays tight; a wide gap betrays cells falling behind.
A battery is a choir of hundreds of cells that should all sing the same note. ΔV (delta-V) measures how out of tune that choir is: the distance between the highest- and lowest-voltage cell at the same moment.
When they all track together, ΔV is small and the pack is healthy. When one or several lag, the gap opens. That's why SOHpro watches it: imbalance can surface before overall SoH shows the damage.
It's always handled in volts (e.g. 3.714 V) and shown in millivolts at the end, because the differences are fine.