SoH
State of Health
The percentage of capacity a battery has left versus when it was new. If your EV left the factory at 100 and holds 90 today, its SoH is 90%.
SoH (state of health) is to a battery what engine wear is to a gas car: the measure of how much is left. A new battery starts at 100% and slips down slowly over the years and the miles.
Don't mix it up with SoC, the state of charge. SoC is how full the battery is right now (like the fuel gauge); SoH is how big the tank still is. You can have the tank at 100% (SoC) on a battery that's already lost capacity (low SoH).
Nobody can measure SoH directly outside a lab — it's estimated. The number your car's computer shows is the manufacturer's own estimate, sometimes a conservative one. SOHpro produces an independent estimate from your scan data, so you get a second pair of eyes.