leafOpen a Leaf battery screen and the abbreviations arrive quickly: SOH, SOC, Hx and Ah. They look precise, sometimes down to two decimal places. Precision on a screen is not the same as certainty about a battery’s future. Start by separating what each figure is trying to describe.
SOH: the controller’s capacity estimate
State of health describes the controller’s estimate of capacity relative to a reference condition. In Leaf Pro, the health card uses the supported battery-controller response. It is reported data, not a fresh independent laboratory capacity test performed by the phone.
Suppose two otherwise comparable cars report 90% and 80% SOH. The first reports more retained capacity on that measure. That does not establish that it has ten percentage points more remaining life, or that it will drive ten percent farther on any route. Consumption, usable charge window, temperature and individual cell behaviour still matter.
SOC: how full, not how healthy
State of charge concerns the battery’s present charge level. Imagine a new container and a smaller worn one, each filled to the top: both can be “full”, but they do not hold the same amount. The analogy is imperfect, yet it captures why 100% SOC cannot establish 100% health.
The car dashboard and an OBD app can also use different charge scales. Leaf Pro displays the controller’s supported reading; it need not match the dashboard percentage exactly. That difference is a reason to check the source, not immediate evidence of a faulty battery.
Hx: useful context, uncertain interpretation
Hx is a separate controller indicator. It is often associated with battery conductance or resistance in technical discussions, but it is not a directly calibrated resistance reading and should not be substituted for SOH. The app preserves it because it is part of the battery information available, not because a single Hx cutoff can diagnose every pack.
If somebody says “never buy below X Hx”, ask what model, measurement conditions and validation support that rule. A number repeated in enough posts can feel authoritative without becoming a manufacturer specification. Compare Hx with the broader evidence instead of treating it as the deciding vote.
Ah: charge capacity with a pack-specific reference
Amp-hours describe charge capacity. Energy in kilowatt-hours additionally depends on voltage. That is why converting an Ah number directly into kWh without a suitable voltage basis is not valid, and why comparing Ah across unlike pack designs is misleading.
For long-term records, Ah is useful when you keep the same car and known pack configuration in view. If a replacement pack or incorrect pack setting enters the story, note it explicitly rather than drawing a continuous trend through the change.
How to use the numbers together
| Question | Start with |
|---|---|
| How full is the car now? | SOC and the vehicle’s own charge display |
| How much capacity does the controller report retaining? | SOH and pack-appropriate Ah context |
| Are some cell pairs behaving differently? | Cell voltages across comparable conditions |
| Can this car do my route? | Recorded consumption, available energy and a safety reserve |
| Is a repair or warranty claim justified? | Qualified diagnosis and the applicable manufacturer process |
Keep a record worth comparing
Save the date, vehicle, pack, charge state and temperature alongside the readings. Include actual driving symptoms if there are any. A Full Assessment adds recorded cell behaviour and coverage, while ordinary journey records can help track real use. No combination of screenshots replaces the physical checks needed for a buying or repair decision.
Leaf Pro keeps the health indicators together but leaves missing data missing. That is preferable to filling an unavailable value with an attractive zero. If the value is stale, reconnect and wait for fresh readings before interpreting it.