Is your EV taking longer to charge than you thought? Or has it stopped charging altogether? While faster charging power often means shorter charging times, several factors can slow things down. Think of EV charging like a team effort: for everything to run smoothly, all the "players"—from your home’s power supply to the car’s battery—need to work together seamlessly.

In this article, we’ll break down what affects your EV charging speed and how to identify possible issues.

Electricity power grid

The electrical system in your home plays a key role in determining how quickly your EV can charge. The voltage and phase setup essentially act as the infrastructure for power delivery—think of it like the size and capacity of a highway for electricity.

In Norway, most homes operate on a 230V (IT) grid, which can deliver a maximum charging capacity of 11kW with a 3-phase connection. If your home is set up with a 1-phase connection, the available power is reduced, resulting in slower charging speeds. Homes with 400V (TN) grids and 3-phase setups typically allow for faster charging because they support higher power throughput.

Zaptec charging stations adapt to various electrical setups, supporting IT and TN installations with up to 32A on 1-phase and 3-phase connections.

To check your home’s electrical setup, refer to the main electrical panel or fuse box. It should have labels indicating whether you have a 230V (IT) or 400V (TN) grid and whether the connection is 1-phase or 3-phase. If you’re unsure, consult an electrician or check the documentation provided by your utility company.

The circuit breaker

The circuit breaker in your home controls how much electricity can flow to the charging station. If the circuit breaker has a lower capacity than what your charging station supports (e.g., 32A for 1-phase or 3-phase), it will limit the maximum charging speed. The circuit breaker is designed to match your home's electrical setup and ensures safe operation. 

Charging cable

Cables come in different capacities, ranging from 16A 1-phase to 32A 3-phase. Think of it like a hose delivering water - a thinner hose can’t deliver as much water at once, and the same goes for cables with lower capacities. To get the fastest charging, ensure your cable matches the capacity of your car and charger.

On-Board Charger (OBC) / The car

Every EV has an On-Board Charger (OBC), which controls how fast the battery can be charged. Your car’s OBC is like a bucket with a specific size—it decides how much water (electricity) can be poured in at once. If your car’s OBC is small, it will limit the charging speed, even if your charger and cable can deliver more. Most EVs charge between 3.3kW and 22kW, depending on their OBC.

Load balancing (Zaptec Sense or third party apps)

If your charging slows down or stops, load balancing might be the cause. Load balancing is a module that can help regulate your charging to avoid overloading your home’s electrical system. A load balancer is typically connected to your fuse box, such as Zaptec Sense or third-party modules like Tibber or Enegic. 

Think of the module as a traffic cop managing electricity flow. If other appliances are using a lot of power (like an oven or washing machine), the system reduces the power sent to your car to prevent overloading.

If you have a load balancer installed, it’s important to understand that it may temporarily lower your charging speed during peak household energy usage. Once demand decreases, the charging power will automatically adjust back up.

Monitor your charging

You can check how much power is being allocated to the car in the Zaptec Portal. If it’s too low, it may just be a matter of waiting until more power is available.

• Log in to the Zaptec Portal and find the installation. Go to Settings > Energy Management and you can see how much power is being released per phase at the bottom: 
  
  
• Under Circuits, you can see how much power (in kW) is currently being offered to the car.

By knowing how your load balancer works, you can better understand and manage your charging experience.

• Zaptec Go uses a 4-pole relay, which opens and closes all phases at the same time. If one phase is heavily loaded, the system may reduce or pause charging to protect the electrical installation. This is a normal part of load balancing and ensures safe operation.
  Zaptec Go meets IEC 62955, ensuring compliance with safety standards for EV charging.
  The built-in four-pole relay disconnects all phases simultaneously, following IEC 61851-1 requirements for electrical protection. Since all phases are controlled together, phase imbalance can impact charging, especially when using Active Power Management (APM).
  
  The available current is determined by the most loaded phase, which affects charging speed. The station only sends a PWM signal indicating the maximum current, while the vehicle decides which phases to use without balancing the load between them. If the vehicle draws more power than allowed, the four-pole relay will cut the power to protect the system. Since there is no phase balancing or switching, the lowest available current determines the charging capacity to prevent overloads.
  
  In a 3-phase setup, a major phase imbalance can prevent charging from starting (at least 6A per phase is required). To improve charging performance, Zaptec Go can be connected to the least-loaded phase, the phase load can be balanced, or the property's main fuse can be upgraded.
  
  Charging current is always the same across all connected phases, as required by IEC 61851-1. This is independent of e.g Zaptec Sense, Tibber Pulse, Perific, other APMs or the four-pole relay.

Offline charging station

Sometimes, the charging station itself goes offline, which limits charging speed to protect the system. You can check the station’s status in the Zaptec app or portal.

If it’s offline, try disconnecting and reconnecting the charger. You can also bring it online through the app.

Temperature and charging speed

Temperature affects how efficiently your EV charges. Let’s break it down:

High temperatures: When charging, the flow of electricity generates heat. For example, the Zaptec Go charging station uses six sensors to monitor key points, such as the energy meter, charging connector, and internal components. If it detects excessive heat—caused by direct sunlight, poor ventilation, or high outdoor temperatures—it can reduce power temporarily to cool down. This ensures safe and reliable operation.

Low temperatures: Cold weather can slow down charging because EV batteries work best within a certain temperature range, typically between 20°C and 30°C. If the battery is too cold, its management system (BMS) will limit charging power to protect the battery. This can lead to longer charging times, especially in winter. Some EVs and chargers include features to preheat the battery, which helps improve charging speed in cold conditions.

Factors influencing temperature include exposure to sunlight, limited airflow around the charger, installation on insulating surfaces, and cables with small cross-sections. Keeping the charger in a shaded and ventilated area can help maintain optimal charging performance.

Zaptec is continually improving its technology to balance safety and performance, ensuring fast and reliable charging even in challenging weather conditions. 

Updated 28 February 2025 13:49