A high-power DC charger does not deliver its maximum rated output throughout every charging session. The power shown on the screen depends on what the vehicle can accept, what the charging equipment can supply, and how much power the site makes available.
For charging station operators, this creates a practical challenge: how do you distinguish normal charging behavior from a configuration problem or equipment fault?
From a manufacturer’s perspective, the answer starts with understanding the relationship between the vehicle, the charger and the site. A low charging rate is a symptom to investigate—not enough evidence on its own to identify the cause.
Rated Power and Actual Charging Power Are Different
A charger’s kilowatt rating describes its maximum output under specified operating conditions. It does not mean every connected vehicle will receive that power.
The vehicle’s battery management system determines an acceptable charging request based on battery condition and operating limits. The charger supplies power within its own electrical capability and the restrictions applied by the installation.
Vehicle manufacturers make this distinction too. Tesla, for example, identifies battery state of charge, temperature and vehicle configuration as factors affecting Supercharging speed.Tesla Support
For operators, the first useful question is therefore: Is the charger delivering less than the vehicle requests, or is the vehicle requesting less than expected?
These situations require different investigations.
Start with the Vehicle and Battery
A vehicle’s advertised peak charging power is only one point on its charging curve. For operational planning, the time required to charge through a relevant battery range is often more useful than the highest number reached briefly.
As the battery fills, the vehicle typically reduces its charging request. Temperature also matters: a cold or overheated battery may accept less current, even when the charger has spare capacity. Battery preconditioning can help on supported vehicles, but its operation depends on the vehicle and the journey.
This makes uncontrolled comparisons misleading. Two identical vehicles can produce different charging results if they arrive with different battery temperatures or starting charge levels.
When investigating a complaint, record the vehicle model, starting battery percentage and preconditioning status. Where available, include battery temperature and the vehicle’s requested charging values.
Check Voltage and Current Before Comparing Kilowatts
One of the most common procurement mistakes is comparing chargers by rated power alone.
DC output power follows this relationship:
Power (kW) = Voltage (V) × Current (A) ÷ 1,000
Consider a hypothetical 240 kW charger fitted with a connector limited to 300 A:
| Actual charging voltage | Connector current | Calculated output |
|---|---|---|
| 400 V | 300 A | 120 kW |
| 600 V | 300 A | 180 kW |
| 800 V | 300 A | 240 kW |
These calculations assume the charger can supply the stated current at each voltage and no other restriction applies. They illustrate electrical limits, rather than any particular OLINK model.
A vehicle charging at 400 V would require 600 A to receive 240 kW. If the selected charger or cable cannot provide that current, the charger’s nameplate power cannot be reached at that voltage.
Also, “400 V” and “800 V” describe vehicle architecture classes. Actual battery voltage changes during charging.
Buyers should request the charger’s output voltage range, continuous current capability and power-versus-voltage curve. A statement that a charger supports both vehicle classes does not establish that it delivers its full rated power to both.
Understand What Happens When Another Vehicle Connects
Multiple connectors do not necessarily represent independent power supplies.
Charging systems may use shared cabinets, fixed output allocations or configurable power distribution. ABB’s published Terra documentation, for example, describes different operating modes with different rules for distributing power between outlets. This demonstrates why the exact equipment configuration matters.
Before ordering a dual-connector charger, establish:
- The total cabinet output.
- The maximum power and continuous current available at each connector.
- The output available during simultaneous charging.
- Whether unused capacity can move between connectors.
- How allocation responds when a session starts or ends.
For a busy public station, simultaneous-session performance can have a greater effect on customer waiting time than single-vehicle peak power.
Separate Site Restrictions from Equipment Problems
A functioning charger can operate below its hardware capability because the site applies a lower power limit.
During diagnosis, review the configured charger limit alongside any energy management or backend charging schedule. Compare the timing of the power reduction with other charging sessions and changes in building demand.
The measurement boundary matters as well. Grid input power, charger DC output and energy stored in the vehicle battery are different quantities. Conversion losses and auxiliary loads mean they should not be treated as interchangeable.
If the available site supply is inadequate, replacing a working charger with a higher-rated unit will not increase the available electrical capacity. The installation and operating strategy need review.
Use Repeatable Tests to Locate the Restriction
A structured comparison is more informative than a screenshot of low charging power.
The following observations provide starting points for investigation; they do not establish a diagnosis by themselves.
| Observed behavior | Useful next check |
|---|---|
| One vehicle charges slowly while others perform normally | Vehicle charging curve, battery condition and compatibility |
| Output drops when a second vehicle connects | Cabinet allocation rules and simultaneous output limits |
| Several chargers reach the same power ceiling | Site controls, backend schedules and supply constraints |
| Power falls after sustained operation | Temperature records, cooling status and recorded derating events |
| Only one connector repeatedly underperforms | Connector condition, sensors and associated hardware |
| Performance changes after a software update | Firmware, configuration history and session logs |
Where diagnostic access permits, compare the vehicle’s requested current with delivered current over the same time interval. Then check whether an equipment or site limit explains the difference.
Not every monitoring platform exposes all the required information. Vehicle requests, internal temperatures and detailed derating reasons may require manufacturer service tools or additional integration. Confirm data availability before relying on a dashboard for technical diagnosis.
If logs point to cooling faults, damaged contacts or electrical protection events, qualified service personnel should follow the manufacturer’s maintenance procedures. Increasing setpoints without finding the cause can undermine protective controls.
Define Performance Before Buying the Charger
For commercial projects, acceptance criteria should describe measurable operating conditions.
Specify the intended vehicle mix, charging voltage range, required connector current, simultaneous-session demand and installation environment. Agree on a test method that can verify the equipment’s capability without relying on one vehicle’s changing battery behavior.
A charger analyzer or suitable load equipment can help assess output capability under controlled conditions. Vehicle testing remains necessary to assess interoperability.
Operators should also track energy delivered and charging duration over comparable sessions. These measures help reveal whether an apparent power problem is affecting service performance.
Discuss Your Project with OLINK
Selecting a DC charger requires matching electrical capability to the vehicles and the site.
For an OLINK project review, share your target vehicle models, installation country, available supply capacity, connector requirements and expected number of simultaneous charging sessions. The proposed model’s output characteristics, cooling requirements, power allocation and software integration should then be confirmed against those requirements.
