EV charger [Charging slower than expected]what to check

A charger delivering less than its rated power is much more often working correctly than failing, and there are four published explanations worth checking before you conclude anything. The first is load balancing. Many installations include a current transformer clamp on the incoming supply so that the charger can back off when the rest of the house is drawing heavily. Put the oven, the shower and the kettle on together and the charger will throttle itself, which is exactly what the clamp is for.

Ohme publish a specific consequence of that system going wrong, in the load balancing section of both the ePod and Home Pro manuals: once load balancing is activated, if the CT clamp is removed or is faulty, the unit will revert to 16 amps. That is a published, specific cause for a charger that has suddenly and permanently limited itself to around 3.7 kilowatts, and it is worth knowing because it looks exactly like a failing charger. The ePod manual adds a second published behaviour of the same system: where the capacity available to the charger drops below 6 amps, the ePod pauses charging for at least five minutes rather than switch the car on and off around the threshold, which is why a heavily loaded house can produce stop-start charging rather than merely slow charging. The second is a solar or surplus mode. If the charger is set to use only surplus generation, it will start, stop and vary its rate as clouds pass, and on a dull day it will do nothing at all. That is the mode working. The third is thermal. Chargers reduce output when they get hot, and myenergi publish it in two stages: wavy lines above the zappi icon mean the unit is thermally limiting with the output power temporarily reduced, and an Overheating! message means the output has been switched off, with a specific remedy for that: make sure the unit is properly ventilated, for example that it has not been covered, and the charge will resume once it has cooled down.

A charger in direct afternoon sun, or with something leaning against it, can throttle for entirely mundane reasons. The fourth is the vehicle, and it is the one people forget. A car's onboard charger sets the ceiling for alternating current charging regardless of what the chargepoint can supply, so a vehicle limited to 3.7 or 7 kilowatts will charge at that rate on a 22 kilowatt unit. Battery temperature and state of charge also matter — a cold battery accepts power slowly, and most cars taper as they approach full.

1. 1

   Check what your car can actually accept on alternating current. A vehicle limited to 7 kilowatts will charge at 7 kilowatts on any home charger, and that is the most common answer.

2. 2

   Look at what else is running in the house. Load balancing will back the charger off while the oven and the shower are on, and restore it afterwards.

3. 3

   If the limit is constant and sits around 3.7 kilowatts, suspect the CT clamp. Ohme publish that a removed or faulty clamp makes the unit revert to 16 amps.

4. 4

   Check which mode the charger is in. A surplus or solar mode is meant to vary with the weather and is not comparable with a full-rate charge.

5. 5

   Make sure nothing is covering the unit and it is not baking in direct sun. myenergi publish ventilation as the remedy for their overheating state, and on a zappi the wavy lines above the unit icon are the sign it is already limiting.

6. 6

   Compare a cold morning with a mild evening. Batteries accept power more slowly when cold, and most cars taper as they get near full, so the same charger can look quite different on two nights.