It's not the charger. More often than not, the root cause lies in the earthing system.
At SCharge, we design and manufacture EV chargers with layers of built-in protection — RCDs, insulation monitoring, temperature sensing, and fault detection. Yet the single most common reason an installation becomes unsafe has nothing to do with the charger hardware itself. It's the ground beneath it.
A charger is only as safe as its connection to earth. Get the earthing wrong, and every protective device inside the unit is fighting with one hand tied behind its back.
Why Earthing Matters More for EV Charging
EV chargers are unlike most electrical loads. They deliver high power, often outdoors, into a vehicle that a person is physically touching while it charges. AC chargers push 7 to 22 kW; DC fast chargers can move hundreds of kilowatts. In a fault condition, the energy available to cause harm is enormous.
The earthing system is what stands between a fault and a fatality. When insulation fails or a live conductor touches an exposed metal part, the earthing system does two things: it carries the fault current safely into the earth, and it gives the protective devices (RCBs, RCDs) a clean, low-impedance path so they trip within milliseconds. If that path is missing, high in resistance, or corroded, the charger's protection cannot operate the way it was designed to — and the metal enclosure the user is touching can become live.
A proper earthing system protects three things at once: the people using the charger, the equipment itself, and the investment behind the installation.
💡 Did you know?
Every SCharge DC and AC charger comes with Continuous Earth Monitoring as standard feature.
Most chargers check the earth once, at power-up, and then assume it stays healthy or only provide earth leakage soluton. SCharge chargers keep checking it for the whole time they are in service, whether idle or charging.
- Real-time earth integrity check: the charger keeps verifying that the protective earth (PE) path is present and healthy.
- Fail-safe response: if the earth is lost or goes out of limits, the charger won’t start a session. If a session is already running, it shuts down safely.
- Remote visibility: earth faults are logged and reported to the CMS over OCPP, so operators find out before a user is at risk, not after.
A broken earth gives no warning on its own. Continuous monitoring makes sure your charger notices it.
Poor Earthing Can Break the Conversation Between Charger and Car: SLAC Failures in DC Chargers
Earthing doesn’t only affect safety. On CCS DC chargers, it also affects whether a session starts at all.
Before any power flows, the charger and the EV pair up using SLAC (Signal Level Attenuation Characterization), defined in ISO 15118-3 and DIN 70121. SLAC runs over HomePlug Green PHY power-line communication, which is injected onto the Control Pilot (CP) line. CP is referenced to Protective Earth (PE). So the PE conductor is effectively half of the communication channel.
When the earth is poor, that channel gets worse:
- Weak or distorted PLC signal: high-impedance or floating PE attenuates the carrier. The signal strength measured during SLAC drops, and matching can time out.
- Noise injection: a shared or corroded earth picks up switching noise from other loads (VFDs, inverters, neighbouring chargers). That raises the noise floor on the CP line.
- Wrong-vehicle matching: at multi-charger sites with a common or poor earth, PLC signals can cross-couple between dispensers. A charger may hear a neighbouring EV, which leads to association errors or failed matching.
- Intermittent session failures: the classic field symptom. The car plugs in and handshakes, then the session fails at “SLAC timeout,” “communication error,” or “precharge failed.” It works on one vehicle and not another, or on dry days but not after rain.
These failures are often blamed on the charger or the vehicle firmware. In many cases, the real culprit is in the ground.
Our field recommendation: if a DC site shows repeated Sesion or communication failures, test the earth first. Check earth resistance, PE continuity at the connector, and N–PE voltage before changing firmware or hardware. A dedicated, low-resistance earth per charger, as described above, is one of the most effective fixes for unreliable session starts.
Anatomy of a Safe EV Charging Installation
Every safe installation is a chain, and each link has a job to do:
EV Charger — Delivers power to the vehicle for safe and reliable charging. This is where users focus, but it's only the visible tip of the system.
Circuit Conductors — The live and neutral cables that carry power from the distribution panel to the charger.
Distribution Panel — Houses the RCBs and MCBs that provide circuit protection. These devices detect overcurrent and earth-fault conditions and disconnect the supply — but only if the earthing gives them a reference to work against.
Earthing Conductor — Provides a dedicated, safe path for fault current to travel from the charger back toward earth.
Earthing Grid — Provides a low-impedance path for fault current and helps reduce fault loop impedance across the site. This is critical: low fault loop impedance is what lets protective devices trip fast enough to save a life.
Earth Electrode — Safely transfers the fault current into the mass of the earth, dissipating it harmlessly.
When all six links are correctly specified and maintained, a fault becomes a non-event: the system detects it, disconnects it, and nobody is any the wiser. When one link is weak, the whole chain fails at the worst possible moment.
Where Installations Go Wrong
In the field, unsafe chargers rarely fail because of the charger. The recurring culprits are:
- High earth resistance — an electrode driven into dry, rocky, or high-resistivity soil without proper backfill or enhancement, leaving fault loop impedance too high for RCBs to trip reliably.
- Corroded or undersized earthing conductors — connections that looked fine at commissioning but degrade over years of moisture and temperature cycling.
- Missing equipotential bonding — exposed metal parts that aren't tied together, so a fault can create a dangerous voltage difference between two things a person might touch simultaneously.
- No periodic testing — earthing is treated as "install once, forget forever," when in reality earth resistance drifts with seasons, soil moisture, and age.
A critical point worth stating plainly: the earth path exists solely to provide safety, and it must always remain live and continuous. Unlike a live or neutral conductor, the earth path carries no current in normal operation — its entire job is to be ready, at any instant, to carry fault current away from a person. That means it must present an unbroken, low-resistance connection from the charger's chassis all the way to the earth electrode, at all times. If any part of that path is compromised — a loose terminal, an undersized conductor, or a burnt earth track on the PCB — the safety function is silently lost. The charger will keep working normally, giving no indication that the one thing standing between the user and a fatal fault has been broken. A burnt or discontinuous earth track is not a cosmetic defect; it severs the protective path exactly where it needs to be strongest, and any such observation should be treated as a safety-critical failure and rectified immediately.
None of these show up on a casual inspection. The charger powers on, the vehicle charges, everything looks normal — until a fault arrives and the safety system that was supposed to be there simply isn't.
Why an EV Charger Needs Its Own Independent Earth
If there is one earthing decision that separates a genuinely safe EV installation from a compromised one, it is this: an EV charger should have its own dedicated, independent earth electrode — not a shared or borrowed one.
It is tempting, especially on retrofit sites, to simply tap into an existing building earth or share the earth pit that already serves the mains distribution. This is one of the most consequential mistakes in the field, and here is why it matters:
- Fault currents stay contained. With a dedicated earth, a fault in the charger is dissipated through its own electrode rather than being pushed back through a shared conductor into other equipment, wiring, or the building. A shared earth turns one charger's fault into everyone's problem.
- No dangerous potential rise on shared metalwork. When a large fault or surge dumps current into a shared earth, the resulting rise in earth potential can appear on unrelated exposed metal parts elsewhere on the site — pipework, other enclosures, even other chargers — creating a shock hazard far from the actual fault. An independent electrode keeps that potential rise localised.
- Clean reference for leakage and fault detection. DC fast chargers in particular rely on precise leakage-current and insulation monitoring. A shared, noisy earth polluted by return currents and harmonics from other loads can cause both nuisance tripping and, worse, masked faults. A dedicated earth gives the charger's protection a clean, stable reference to work against.
- Predictable, testable resistance. A dedicated pit can be sized, tested, and maintained to a known earth resistance value for that specific charger. A shared earth's resistance changes every time something else is added to the site, so the charger you commissioned safely today may be sitting on a degraded earth tomorrow without anyone touching the charger itself.
- Prevents circulating and neutral-to-earth currents. Sharing an earth path with the supply neutral or with heavy loads is a common source of the very circulating currents that show up as heating — and, in the extreme, as a burnt earth track. An independent earth breaks that loop.
For EV charging, the earth is not plumbing to be shared for convenience — it is a safety instrument, and it should be dedicated to the job. Our recommendation for every deployment is a properly designed, independent earth pit per charger (or per charging island for larger DC installations), sized to soil conditions and verified by measurement — with periodic re-testing built into the site's maintenance plan.
The SCharge Approach
We build our AC and DC chargers to IS 17017 and IEC 61851 standards, with protection systems engineered for real-world Indian conditions. But we also know a truth every serious infrastructure engineer eventually learns:
A strong infrastructure begins with a strong connection to earth.
That's why we treat earthing not as an afterthought but as a first-class design input for every deployment. When we work with CPOs and site owners, we look at the whole chain — soil resistivity, electrode design, conductor sizing, bonding, and a testing regime — not just the box on the wall.
Because the safest charger in the world is only as safe as the earth it stands on.
SCharge is a Made-in-India EV charging hardware and software company, engineering AC and DC chargers, CMS software, and energy infrastructure for a reliable electric future. To discuss safe, standards-compliant EV charging deployment for your site, get in touch with our team.