Note: For a full breakdown of Power Management functionality, visit the power management technical reference guide.
Power management overview
Your dashboard's power management solution has several features and capabilities to support complex commercial installations and maximize the efficient utilization of power capacity to save site hosts on infrastructure costs, including:
Flexibility: The system can model a variety of complex installations, such as multiple circuits for a location and a hierarchical model that can support tiers of nested sub-panels under main panels
3-phase power: Charger phase wiring is represented to allow for power allocation by phase. This allows for the most efficient use of available capacity, and greater efficiency leads to reduced costs for site hosts. Other power-consuming devices sharing circuits with chargers are represented in phase wiring
Reallocation of power: When vehicles reach full charge and charging slows down, power is reallocated to other chargers to maximize efficient utilization of available capacity. This efficiency yields faster charging speeds for drivers and further cost savings for site hosts.
Round robin for over-subscription: If a breaker is oversubscribed by chargers such that even their minimum charging power (e.g. 6A) would exceed the breaker’s limit, power is allocated in a round robin fashion to keep power within safe operating limits. This is useful for long-term parking use cases, such as airports.
How does my dashboard's power management work?
Approved EV charging hardware connects to the charging station management system (CSMS) through 4G, Wi-Fi, or Ethernet. We use the Open Charge Point Protocol (OCPP) to communicate with EV chargers and we use OCPP’s Charging Profiles to facilitate power management with compatible EV chargers.
The diagram below shows an example of our EVEMS in action with four 32 A EV chargers installed on a circuit that only has 80 A of power available. Power is distributed based on the number of EVs plugged in and requesting a charge, but never exceeds 80 A.
To benefit from full dynamic power management, customers must maintain an active subscription to the charging station management system (CSMS), which includes our EVEMS.
How do I set up power management?
Presently, power management must be set up by the Power Management Team working in conjunction with the certified electrician that is installing your EV chargers. Power management is not enabled by default when deploying a new EV charging site.
What is the maximum number of chargers put on the same circuit?
There is no software limitation for the number of chargers that can be set up on the same circuit. We advise against severe over-subscription, since OCPP EV chargers have a minimum amperage they will output while still delivering a charge. The minimum amperage most Level 2 chargers will output is between 6–8 A, but this varies depending on manufacturer.
For a 100 A panel or circuit, we set a usable limit of 80% or 80 A within our system. If you are deploying chargers with an 8 A minimum output, we would recommend deploying a maximum of 10 chargers on the 100 A circuit. This is because 10 × 8 A = 80 A, or 80% of the circuit’s limit.
If you are deploying chargers with a 6 A minimum output, you could deploy up to 13 chargers on the 100 A circuit (13 × 6 A = 78 A).
Assuming the installation of 32 A EV chargers, only 2.5 chargers would fit on a 100 A circuit without power management. Using the examples above, power management enables an expansion ratio of 1:4 in the case of chargers with an 8 A minimum, and greater than 1:5 in the case of chargers with a 6 A minimum.
In general, you can calculate the oversubscription rate that a given charger will support using an equal charger algorithm by dividing the output power of the charger by the minimum amperage. A 32 A EV charger with a minimum output of 8 A would support oversubscription of 32 A ÷ 8 A = 4. So you could quadruple the number of chargers your infrastructure would support without power management. An 80 A EV charger with a minimum output of 8 A would support oversubscription of 80 A ÷ 8 A = 10. Or 10× the rated capacity.
If the chargers you are installing support 0 A Charging Profiles, you can expand a circuit even further by using round-robin charging.
Does my dashboard's power management load balance in real time?
This power management system is designed to re-allocate amperage any time there is an update to the status of a charging session.
Here is what happens when a new car plugs into a charger that is part of a power management group:
- The vehicle requests a charge from the charger. The charger communicates this request with the CSMS.
- The CSMS re-calculates power allocation based on the selected algorithm.
- Before power is allocated to the new vehicle, the system will first reduce the power for ongoing
sessions to ensure a safe transition. - After the system has confirmed successful decrease of power across all ongoing sessions, the new session will begin for the vehicle that just plugged in and requested a charge.
In practice, the process above will usually take place in a fraction of a second. This makes a power
re-allocation feel virtually real time. In reality, there are checks and balances that take place before power is reallocated.
How is billing and access control handled?
Power management groups, access control groups, and pricing groups are all separate in the system. This means that chargers can be part of the same power management group but different access control or pricing groups.
If chargers use a “bill by kWh” pricing profile, power management is already accommodated for, since reducing output power will also reduce the kWh that a vehicle uses.
If chargers use a “bill by time plugged in” pricing profile, then there is no accommodation for power
management. End users will be billed the full hourly amount for the entire time they are plugged in.
If chargers use a “bill by effective time charging” pricing profile, your dashboard system automatically pro-rates the billing rate based on power management. For example, if a charger bills $2.00 per hour but a power management profile reduces output power by half for a certain time period, the end user will only be billed $1.00 per hour for that time period.
Are there limitations to my dashboard's power management system?
Your dashboard's power management only works with supported EV chargers. Just because an EV charger claims OCPP compliance does not mean it will work with this power management system. If you are unsure if your hardware is supported, please contact Support.
Your CSMS and power management system depends on chargers maintaining an active connection to the internet. The system is designed to accommodate individual chargers dropping offline from time to time, but it cannot do anything to control chargers that remain disconnected for long periods of time.
Is my dashboard's power management system cloud-based or local?
Your dashboard's power management is a cloud-based system with offline redundancies. We rely on EV chargers being connected to the cloud and communicating to our CSMS most of the time, but the system is designed to accommodate EV chargers that drop offline temporarily.
If all chargers are offline, power management will not work.
Cloud-based power management provides more flexibility to adjust the system over time. It also combines load balancing with other CSMS functionalities like monitoring, reporting, billing, or access control.
Is there a user interface (UI) for power management?
Yes. Power management is accessed via the “Power” tab on the navigation sidebar of the dashboard.
The electrical infrastructure is represented, including:
All main panels and any sub-panels for a circuit with chargers with their names/labels, breaker ratings, and maximum continuous load.
Charger phase wiring
Other power-consuming devices sharing a circuit with chargers (referred to as “unmanaged loads” in the dashboard)
What happens if the power managed chargers go offline?
If chargers lose internet connection, power limits will still not be exceeded thanks to fallback amperages on individual chargers. Chargers can also be configured to only initiate a new charging session while they are online, ensuring no additional load is added until internet connection is re-established.