How reliable is EV charging?
German e-mobility company EcoG has developed an index to measure the reliability of different EV platforms. EcoG first published a report in 2023. Its “Charging Reliability Index” compared ten unnamed vehicle models. Two years on, the second edition expands the scope to named EV platforms: BMW UKL2, Ford GE1, Geely SEA, Hyundai E-GMP, Lucid Air, Mercedes MFA2, SAIC LWB, Stellantis CMP, Tesla Model 3/Y and VW’s MEB architecture.
EcoG’s core business is developing operating software for DC charging stations. This naturally puts the company in close contact with questions of charging reliability. “Concerns about EV charging reliability are replacing range anxiety as one of the biggest hurdles for the adoption of electric mobility. Studies show that still 1 in 10 charging attempts fail,” the company notes. The Munich-based team stresses that the vehicle-side interface is a decisive factor. The 2025 CRI is based on 20 tests, “categorised as Charging Initialization, Charging Process, Error Recovery and User Communication.”
Compared with 2023, EcoG has added new test categories, increased the number of tests by 50 per cent and, for the first time, included bidirectional DC charging.
Results vary widely
EcoG names the tested platforms but anonymises the outcomes. Only one platform scored above 76 points out of 100. “This shows that fundamental flaws still remain, which can cause substantial confusion and frustration among EV drivers and even breakdowns of EVs on the road,” the analysts conclude. The lowest-performing platform managed just 39 points.
The study highlights improvements in charging stability compared to 2023. “Higher control signal quality leads to fewer unwanted charging session interruptions.” While two vehicles in the 2023 tests showed dangerously weak communication signals, none were observed in 2025. “This is a promising indicator for an improvement of robustness of EV implementations, leading to more stable and reliable charging sessions.” Yet signal attenuation still varies significantly, with more than 20 dB between the best and worst implementations.
Vehicles wih too-short authorisation windows
Munich-based analysts also see the main cause of failed charging sessions as unresolved: so-called authorisation timeouts stop charging before it actually begins. In many cases, failed charging starts are caused by overly strict and poorly coordinated timeouts between the vehicle and the charger, the report says. The EV driver authorises the charging session at the station (“for example by swiping his credit card and entering a PIN code”), but the authorisation process takes so long that the vehicle (“which is waiting for the session to start since the cable was plugged in”) times out, and the charging session is aborted on the vehicle side.
In tests for the 2025 Charging Reliability Index, EcoG found that four out of ten vehicle platforms still imposed a very strict 60-second authorisation window before the charging session was cancelled. Surprisingly, the analysts observed that in six platforms the timeout varied depending on the protocol version negotiated at the start of the session: “Two platforms showed low timeouts only if ISO but not if DIN protocol is selected. This could be very confusing for the user, since it is not transparent which protocol is used,” the study concludes.
Depleted 12-volt batteries – and nothing works
Another weak point is and remains the 12-volt battery – the small but crucial power source for the vehicle’s control and safety systems. If depleted, the vehicle becomes unresponsive and cannot be started or switched into drive mode without technical assistance. “It has been seen often in the field that this happens if a charging attempt fails and the EV automatically retries to start the process for a long time,” the authors write. Although implementing such retry attempts is intended as a convenience feature, it can become a trap: “Three of the tested vehicle platforms repeated these attempts infinitely,” EcoG notes. “This behavior places a heavy drain on the 12V battery. Overuse of the 12V battery not only reduces its lifespan but can also leave the car completely inoperable at the charging station.”
Beyond these results, EcoG also identified several encouraging developments: seven out of ten vehicles now support higher communication security levels (TLS = Transport Layer Security), improving the protection of sensitive control data during charging. In addition, all tested vehicle platforms ensure that vehicles cannot be moved while still connected to the charger – a basic but essential safety measure. However, there is still room for improvement in verifying the voltage provided by the charger (only five EV platforms check this themselves and do not rely solely on the information supplied by the charger) and in the use of standardised error codes (only two EV platforms use these to clearly notify drivers of issues such as faulty plug locking).
According to EcoG, the user experience also varies widely: three out of ten vehicles still do not offer a simple way to stop charging directly at the vehicle, and two models continue not to support key industry protocols such as ISO 15118-2, limiting interoperability.
Better than 2023, but still room for improvement
The analysts conclude that the EV industry is moving in the right direction, but further action is required: “Taken together, these results show steady progress across the industry but the best CRI value of 76% also highlights the importance of further improving charging interface implementations to achieve a reliable and user-friendly charging experience.”
This article was first published by Cora Werwitzke for electrive’s German edition.
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