SOH is the number that tells you the real story of an EV battery. Whether you are buying, selling, or worried about range — here is what it means and what to do about it.
State of Health (SOH) is a percentage comparing your battery current capacity against its original factory capacity. A new battery starts close to 100% SOH. As the vehicle ages and accumulates charge cycles, that percentage gradually falls — this is degradation.
85% or above is generally healthy. Below 80% you will notice real range impact daily and resale value drops significantly. Aviloo flags anything below 80% as a Red Flag.
Most EVs lose 2-3% SOH per year under normal use. A well-maintained 4-year-old EV should typically sit between 85-93% SOH. Faster degradation suggests charging habit issues or underlying cell faults worth investigating.
Occasional rapid DC charging causes minimal harm. Frequent rapid charging — especially above 80% state of charge or in high temperatures — accelerates cell stress over time. Impact varies by model: Nissan Leaf (no thermal management) is more vulnerable than Tesla or Hyundai.
OBD tools read data the Battery Management System reports about itself — not independent. Aviloo performs a cell-level test that does not rely on the BMS, producing a third-party certified result. Read the full comparison.
PAD is South Wales' only Aviloo certified mobile EV battery testing service. We travel to your address, test in 20 minutes, and email your official certificate the same day.
