# SOH (State of Health)

> Battery health: current capacity vs nominal. 100% = new battery; 70-80% = end of practical service life.

**Categoría**: Technical specifications
**URL canónica**: https://baterias.com/gb/battery-glossary/soh
**Idioma**: en-GB

## Definition

SOH (State of Health) compares the CURRENT capacity of the battery to its NOMINAL factory capacity. A new battery has SOH 100%. With use, sulphation, internal corrosion and loss of active material reduce effective capacity: at SOH 80% an 80 Ah battery actually delivers 64 Ah. **Practical end of service life for automotive use is considered when SOH drops below 70-80%** — at that point CCA has fallen enough to cause cold-start failures. Professional diagnostic equipment (Bosch BAT, Midtronics) measures SOH by injecting a known load and observing the dynamic response; basic voltmeters do NOT measure SOH, only SOC. In Start-Stop vehicles the ECU continuously estimates SOH; when degradation is detected, **it automatically disables the Start-Stop function** to protect engine starting — usually the first sign that the battery is reaching end of life.

## See also

- [SOC (State of Charge)](https://baterias.com/gb/battery-glossary/soc)
- [DoD (Depth of Discharge)](https://baterias.com/gb/battery-glossary/dod)
- [Sulphation](https://baterias.com/gb/battery-glossary/sulphation)

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