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Measured current not correct


I just finished building my openevse and set the max current to 10A. My pilot signal says it's set to 10A as well, but the display of the openevse and the webinterface show me that the car is charging with 8.58A and not taking the full 10A. I'm charging a Hyundai Kona 2019

Also the measured voltage is not correct. It shows that it's connected to 240 volts, but i'm monitoring my house energy meter and I know that 230 volts are entering my house, not 240. Did I connect something wrong?

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Some more information. I'm using this charger in the EU. Bought it from the openevse online store.

Rap $GV: >$OK 7.1.3 5.1.3^22


I'm using a single phase 32a tethered cable. Chargelimit is set to 10A because i'm still using 2.5mm2 input cables. Those will be changed soon to 6mm2.

I also noticed when I reboot openevse while the car is charging, it loses the kWH from this session and doesn't save it to the total kWh, is that how it's supposed to be?

Here is a guide for calibration of the OpenEVSE current sensor: 

Voltage is not measured it is assumes to be 120 for L1 and 240 for L2 in the official firmware. EU firmware versions are avaliable for OpenEnergyMonitor in the UK that use 230 as the default for L2. Here is a guide to set a different value with RAPI:


OpenEVSE saves the session kwh to the total and writes the new value to EEPROM when the vehicle is unplugged. We do not reccomend rebooting during a charge or while a vehicle is plugged in.

I just measured using an amp clamp meter, the openevse is correctly calibrated. But why does it charge with 8.80A when my charge limit is set to 10A?

The Pilot setting of 10A is a maximum do not exceed value. The vehicle on-board charger is responsible for the actual value and may draw any current up 10A but no more.

So when i set my charge limit to 20A, and the display on the openevse unit is showing 18.2A, that's because my Hyundai Kona which has a charge capacity of 32A set it that way?

A AC charging station (EVSE) is just a smart switch it can close (ON) a relay or open (OFF). The station has zero ability to alter the current other than sending out the pilot signal. 

The vehicles on-board charging electronics and battery management systems do all the work to ensure the current is less then the pilot maximum value. 

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encounters a similar problem. there is nissan leaf ze1 with type 2 port. when I set the charging current to 10A in the web interface, the car takes only 6A. you have to set the charge current to 14a in the web interface in order to get a real charge current of 10a. how can I solve this problem ? I did the mains voltage calibration for the l2 level at 230v.
Hi . The solution turned out to be very interesting. First of all, you need to look at the shape of the pilot signal with an oscilloscope. in my case, the edges of the pilot signal were not clear. replacing the op-amp with an lf422 completely solved the problem.


Glad your issue was resolved. However, one of the specifications for the pilot signal is the time to go from low to high. The LF353 just meets this specification with a slew rate of 13v/us, the LF422 has a much slower slew rate of 1V/us. The pilot with the LF422 is likely out of spec, but it may work fine if the vehicles are tolerent.

I have a similar problem and I don't understand how to fix this. 

Here is a guide for calibration of the OpenEVSE current sensor: "

this helps after the charging has started after covering the 3A lead...

The kWh calculation also gives too large numbers apparently for this same reason?

I too have a similar problem charging my Outlander and Tesla even after calibrating the current sensor of the Openevse unit.

My new unit tells the cars to charge at 1A less than the spare PV current across the range.

As a workaround I have altered the spare PV that my emoncms system reports to the EVSE :-

SparePV= PV generated power - House only power + 250W. This gives me near 100% consumption of spare solar with my house battery hovering around 0W charge/ discharge.

I'm not sure if this would be adaptable for zero export setup systems though.

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