1. Minimum EV charger current 

6 A is the standard minimum current for EV chargers, but some cars will not charge at the 6 A setpoint. One possible explanation for this is that there is always some current drop when charging. Some cars will always charge 0-25% lower than the EV limit.  At the 6 A limit, this can be 4.5 A and can be the reason why the car cannot start charging. Under our observation 9 A is the preferred minimum setpoint for EV chargers. 

 

2. Current overshoot when starting offline EV chargers 

There is a new setting under strategy -> advanced settings "Allow short current/power draw over the limit when starting new devices". 

 

A) OFF 

The strategy will reserve the needed current to start 1 more EV charger if possible. It will cycle reservation between chargers until one of them start to charge. Reservation will only be active if we have enough flexibility in fine-tuning the setpoint for running EV chargers without turning them off. 

 

Example 1: 

Limit: 29 A. 

Minimum setpoint for EV: 9 A. 

EV 1: charging 10 A. 

EV 2: charging 10 A. 

EV 3: offline with 9 A setpoint. 

EV 4: offline with 0 A setpoint. 

 

In 10-15 seconds, EV 4 will receive a 9 A setpoint and EV 3 will be set to 0 A. Reservation is cycled between offline chargers. 

 

Example 2: 

Limit: 24 A 

Minimum setpoint for EV: 9 A. 

EV 1: charging 12 A. 

EV 2: charging 12 A. 

EV 3: offline with 0 A setpoint. 

EV 4: offline with 0 A setpoint. 

 

There is no available current to enable EV 3 or EV 4 (9+9+9=27 > 24 A limit). The strategy will increase the limit on EV 1 and EV 2. 

 

B) ON 

The strategy will never reserve any current to start more EV chargers. It will start a new charger over the current limit if there is enough flexibility in fine-tuning the setpoint for running EV chargers without turning them off. When overshoot over the current limit is expected, the strategy will try to start one EV charger at a time by cycling the setpoint. 

 

Example 1: 

Limit: 28 A. 

Minimum setpoint for EV: 9 A. 

EV 1: charging 14 A. 

EV 2: charging 14 A. 

EV 3: offline with 9 A setpoint. 

EV 4: offline with 0 A setpoint. 

 

The strategy is trying to start up EV 3, because it has 10 A of available current from EV 1 and EV 2 without turning them off. In 10-15 seconds, EV 4 will receive a 9 A setpoint and EV 3 will be set to 0 A. The setpoint is cycled between offline chargers. 

 

Example 2: 

Limit: 26 A. 

Minimum setpoint for EV: 9 A. 

EV 1: charging 13 A. 

EV 2: charging 13 A. 

EV 3: offline with 0 A setpoint. 

EV 4: offline with 0 A setpoint. 

 

Not enough available current from EV 1 and EV 2 to start a new charger (4+4=8 < 9 A). 

 

3. Equalizing power between EV chargers 

The strategy will try to equalize the power between all running EV chargers based on power draw. The problem is that strategy does not have any information on how much power the car will request without any limitations. Therefore, equal distribution of power/current limits between chargers is far from optimal. Equal power distribution is the preferred way. 

 

Example of equalizing limit: 

Number of EV chargers: 2. 

Limit: 40 A. 

EV 1: limit 20 A, charging 20 A. 

EV 2: limit 20 A, charging 6 A (car is limiting charging). 

 

Number of EV chargers: 5. 

Limit: 100 A. 

EV 1: limit 20 A, charging 20 A. 

EV 2: limit 20 A, charging 20 A. 

EV 3: limit 20 A, charging 20 A. 

EV 4: limit 20 A, charging 20 A. 

EV 5: limit 20 A, charging 9 A (car is limiting charging). 

 

Example of equalizing power: 

Number of EV chargers: 2. 

Limit: 40 A. 

EV 1: limit 30 A, charging 30 A. 

EV 2: limit 10 A, charging 9 A (car is limiting charging). 

 

Number of EV chargers: 5. 

Limit: 100 A. 

EV 1: limit 22,5 A, charging 22,5 A. 

EV 2: limit 22,5 A, charging 22,5 A. 

EV 3: limit 22,5 A, charging 22,5 A. 

EV 4: limit 22,5 A, charging 22,5 A. 

EV 5: limit 10 A, charging 9 A (car is limiting charging).