If your home EV charger keeps stopping mid-session — the car unplugs itself, the charge pauses repeatedly, or the unit cuts out and restarts — the cause is almost always one of four things: an overheating circuit, a wiring or connection fault, a software scheduling conflict, or an unstable grid voltage. This guide explains each cause and what you can do about it.
Key Takeaways
- Intermittent disconnections are most commonly caused by loose wiring connections at the consumer unit, the charger back-plate, or within the cable connector itself.
- An EV charger on an undersized or shared circuit may trip the breaker when household loads are high — the charger should be on its own dedicated 32A circuit.
- Smart charger scheduling or vehicle charge limits set in the app can look like a disconnection fault but are intentional stops — always check the app first.
- Overheating protection in the charger will cut the session automatically if the unit or cable temperature exceeds safe limits — usually caused by poor ventilation or a cable left coiled during charging.
- Grid voltage fluctuations cause some chargers to disconnect as a safety response — a stabiliser or voltage monitor can confirm whether this is the cause.
Common Causes of EV Charger Disconnections
1. Loose or Deteriorating Wiring Connections
The most frequent cause of intermittent mid-session stops is a loose connection at one of several possible points: the consumer unit terminal block, the charger’s back-plate wiring, or a junction in the cable run. As the cable and connections heat and cool repeatedly over hundreds of charging cycles, terminations can loosen slightly. Loose connections create resistance, generate localised heat, and cause the voltage at the charger to drop — which triggers the unit to cut the session.
Signs this is the cause:
- Disconnections happen at similar stages in the charge (e.g., always after 2 to 3 hours)
- The charger is several years old and has had many charging cycles
- You notice the cable or outlet getting warm during charging
This is a job for a qualified electrician. Do not open the charger unit or the consumer unit yourself.
2. Undersized or Shared Circuit
A 7 kW EV charger drawing 32A continuously is a significant sustained load. If the circuit is shared with other high-draw appliances (washing machine, tumble dryer, electric oven), the combined load can push the total current above the MCB or fuse rating, causing a trip. The trip cuts power to the circuit, which the charger registers as a disconnection.
An EV charger must be installed on its own dedicated circuit. This is a requirement under BS 7671 for circuits rated above 20A. If your charger was installed without a dedicated circuit, or if the electrician at the time shared a circuit to reduce cable costs, have this corrected.
3. Scheduling or Vehicle Charge Limit
Many smart chargers and EVs have charge schedules or battery limits that stop charging at a set time or level. If you set a charging window of 11 pm to 6 am and plug in at 10 pm, the charger will refuse to start — or will start briefly and then pause until the scheduled window opens. This can look like a disconnection fault from outside.
Similarly, if you have set an 80% charge limit in your car’s settings or the charger app, the session will stop when that level is reached — not because of a fault, but because the limit has been reached.
Check the app first. Open your charger app and look at the session log to see whether the stop was scheduled or unplanned. Most charger apps (Hypervolt, Ohme, Zappi, EO) log both scheduled stops and fault-triggered stops differently.
4. Overheating Protection
Most EV chargers and cables have built-in thermal protection. If the charger body temperature rises above its rated limit — typically 60 to 70°C — the unit will pause the session automatically to prevent damage.
This can be caused by:
- Poor ventilation around the charger (installed in an enclosed box or against a surface that traps heat)
- A charging cable left coiled during a session (coiled cables generate significantly more heat than laid-out cables)
- High ambient temperatures (hot garage or south-facing wall in summer)
- An oversized load relative to the cable rating
Allow the charger to cool and ensure the cable is fully uncoiled during sessions. If the charger is installed without adequate airflow, discuss repositioning or ventilation options with your installer.
5. Grid Voltage Fluctuations
UK grid voltage should remain between 216V and 253V (230V nominal, +/-10%). EV chargers monitor the supply voltage continuously. If the voltage drops below or rises above these limits, some chargers will disconnect as a safety measure to protect both the vehicle’s onboard charger and the charger unit itself.
Voltage fluctuations are more common in rural areas with long distribution network runs, and in areas with high concentrations of solar generation on the same local transformer. You may notice disconnections at particular times of day (mid-afternoon in summer when local solar export is highest, or early evening when local load is highest).
A qualified electrician can fit a voltage monitoring device to your supply to confirm whether fluctuations are occurring. If confirmed, your electricity network operator (not your supplier) is responsible for the distribution network — contact them to report the issue.
Diagnosis Steps
- Check the app first — look at the session log and confirm whether the stop was scheduled, a charge limit, or an unplanned cutout
- Check the consumer unit — confirm whether a breaker has tripped coinciding with the disconnection
- Inspect the cable — ensure it is fully uncoiled during charging and that the connector is seated firmly at both ends
- Check charger ventilation — feel whether the charger body is hot after a disconnection; if yes, overheating is likely
- Test at different times of day — if disconnections only happen at certain hours, grid voltage fluctuation is a candidate
- Call your installer if the cause remains unclear after the above steps
When to Call an Installer
Contact a qualified EV installer or your charger manufacturer’s support team if:
- You suspect a wiring fault (the most common cause and one that requires professional diagnosis)
- The charger is warm or hot to the touch at the point of disconnection
- The consumer unit breaker trips coinciding with the charger disconnect
- Restarting the session consistently triggers disconnection at the same point
The EV charger troubleshooting hub covers a wider range of home charging faults, including complete charge failures and consumer unit issues.
Frequently Asked Questions
Why does my charger stop after exactly the same amount of time each night?
This almost always indicates a scheduled stop set in either the charger app or the vehicle settings. Check for a charging window end time, a charge limit, or an economy/eco mode schedule. If none of these account for it, check whether the time correlates with peak household electrical load — for example, if dinner is being cooked and other high-draw appliances are running simultaneously.
Could a software update have caused my charger to start disconnecting?
Yes, this does occur. Some firmware updates change default settings — in particular, load management thresholds or scheduling defaults — that can cause unexpected stops. Check whether the disconnections started around the time the charger or car received a firmware update. If so, contact the charger manufacturer to report the regression; most have a rollback option or will issue a patch.
Is it safe to leave the EV plugged in after a disconnection?
Yes, provided the cable and connectors are not damaged and there are no burning smells. A mid-session stop caused by scheduling, a charge limit, or thermal protection does not damage the vehicle. If you suspect a wiring fault (warm cable, tripped breaker), unplug the car and do not reconnect until the installation has been inspected.