It is both suggested and easy for a user to generate more than one PKC Power checK Control certificate within the same year to monitor the status of their battery. It is equally normal for the reported State of Health (SoH)—or, more precisely, the available capacity—to vary over time.
These variations may include small increases followed by decreases.
Below are the reasons that explain this behavior.
1. The SoH is not a fixed value
What is commonly referred to as the State of Health (SoH) actually represents the available capacity, meaning the amount of usable energy under the specific conditions in which the test is performed.
This value is not static. It is calculated by the vehicle’s Battery Management System (BMS), which relies on multiple parameters that naturally change throughout the year, such as:
- Recent charging habits
- Temperature and environmental conditions
- Driving style
- Depth of discharge
- BMS balancing activity
- Manufacturer updates or recalibrations
As these parameters vary, the BMS may report different usable capacities, resulting in fluctuations in SoH between certificates.
2. Manufacturer (car maker) updates
The vehicle manufacturer may release software updates that modify the internal parameters of the BMS.
Even small changes can alter the operational range of the battery and therefore increase or decrease the available capacity reported in the certificate.
3. Seasonality and environmental conditions
Battery chemistry is sensitive to temperature.
In summer, due to more favorable environmental conditions, the available capacity can appear up to 3 percentage points higher compared to winter months.
During cold seasons, a lower SoH reading is common and expected.
4. How the vehicle is used
Usage patterns also affect the BMS estimation.
A vehicle that is used infrequently may show a slightly lower available capacity than one used regularly, because frequent charge–discharge cycles help the BMS recalibrate more accurately.
5. Short-term increases in SoH are normal
Even in an aging battery, temporary increases can occur.
This happens when the BMS updates its internal estimation and may be caused by:
- A deeper discharge cycle improving calibration
- A full charge followed by a balancing cycle
- Temperature changes that temporarily improve battery efficiency
- A recent software update
- Changes in driving or charging behavior
These are calibration effects, not actual improvements in the physical capacity of the battery.
6. Why a value may decrease after increasing
Fluctuations such as 97% → 95% → 96% → 94% within a single year are typical.
A value may rise temporarily and then decrease due to:
- Lower temperatures
- Completion of a BMS balancing cycle
- Changes in fast-charging frequency
- Prolonged periods at high state of charge
- Reduced vehicle usage, which lowers estimation accuracy
These variations reflect the BMS refining its calculation under different conditions.
7. PKC reports exactly what the BMS provides
PKC Power checK Control combines data provided directly by the vehicle’s BMS with proprietary algorithms, using a multi-test approach to validate and ensure the coherence of the information. No data is modified or manipulated in any way.
The value shown in the certificate is derived from real measurements, harmonized through our algorithms, and based exclusively on data read directly from the vehicle’s BMS at the moment of the test.
Therefore, variations between certificates correspond to real BMS behavior, not PKC errors.
8. Why users may generate multiple certificates within a year
PKC allows up to six certificates per year for private users (one every two months).
Users may generate multiple certificates for:
- Periodic battery check-ups
- Selling or trading the vehicle
- Verifying battery status after maintenance
- After battery replacement
- Seasonal comparison
- General monitoring or curiosity
Each certificate is a snapshot of the battery at that specific moment.
9. Conclusion: fluctuations are normal
Variations in SoH over the year — including temporary increases followed by decreases — are normal and expected.
They reflect the functioning and recalibration behavior of modern BMS systems.
What truly matters is the long-term trend, not short-term fluctuations.
PKC is designed for full transparency: it does not smooth, filter, or adjust data. Every certificate shows the values exactly as reported by the vehicle, representing the real energy available for the vehicle’s actual use in real-world conditions.