EV Charger calibration issues

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question

Harold Halewijn asked Jan 29, '24

EV Charger calibration issues

Hi, I'm using the EV Charger (old style) for 12 months now. Until now I didn't pay attention to the power calibration so I can't tell you if this was differently with previous firmware versions.

If I want to charge 3-phase cars, I have to set the power calibration setting to 0.8 to reflect real power. I can check this with smartmeters in my cabinet. But when I charge a hybrid-car (single phase) I have to change the calibration setting to 1 to see real power taken.

These pictures show the charging of single phase. You can notice the charge rate reported by EV Charger (2783) and the AC loads (4729, there are some small additional loads there).

Above picture is with power calibration set to 0.8

next picture shows right value after changing to 1.

If yoy want, I can supply the same pictures for a 3 phase car.

Why is this?

ev charging station

19

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Lucian Popescu (Victron Energy Staff) ♦♦ commented · Jan 29 at 09:07 AM

Hi, the power measurement is not very precise as we are only measuring the current and not the voltage. So the power displayed is just an approximation

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kudos50 Lucian Popescu (Victron Energy Staff) ♦♦ commented · Feb 14 at 02:55 PM

That's kind of a big oops for me as I'm using the numbers to do expenses every month.

Also, Harold is mentioning 0.8 and 1.0 to get his numbers matching from 3 to one 1 phase. That's a 20% difference whereas he most definitely never ever has a 20% voltage sag during charging.

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kudos50 Lucian Popescu (Victron Energy Staff) ♦♦ commented · Feb 27 at 05:31 PM

If you have a moment @Lucian Popescu (Victron Energy Staff) I think this thread is pretty important for some users including myself. I have also read the thread about users discussing the future/new reporting feature in VRM to charge their company or their employer. All of that is not realistic if the numbers are this far of.

For me there is no way to explain the 20% gap that Harold has experienced just because you don't know the voltage. If his numbers are showing up on other users dashboards as well, this is not "just a minor inconvenience". Specially because people don't even realise they actually have a problem to begin with.

If it's only the voltage that is missing and the current is pretty accurate, it would not be too difficult to "help" those users by writing a flow that sets the EVCS power calibration automatically based on the voltage you are using for your estimations (230 I presume) and the voltage taken from the grid meter or the inverter. This would not be 100% accurate and it will not cover power factor deviations during the start and stop process. But it will come closer than what you have now if charging at night with no wind energy (225V?) or by day if the whole neighbourhood is generating solar (235V and up)?

But all this does not fix nor does it explain the 20% gap.

I had a funny experience myself this afternoon. A friend had his M3SR set to 100% and at the end of the charge process the car was only taking 1kW for a long time. As the house was empty and almost everything is metered I know for a fact there were no other consumers with significance. The ac-load said 1.1kW spread over 3 phases, the car said it was taking 1kW, but the charger said 0W charging. Lasted for over 30mins if memory serves me well. This showed both on VRM and on the charger webpage.

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Lucian Popescu (Victron Energy Staff) ♦♦ kudos50 commented · Feb 27 at 05:43 PM

For me, it's pretty accurate, this is my charging session today.
If you have a meter installed where the EVCS is installed, and you see big differences, we can have a look.

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1709055594696.png (87.9 KiB)

kudos50 kudos50 commented · Feb 27 at 07:44 PM

I did. In fact, not knowing it only measures current I simply added an approved meter in between and charged 2 or 3 times to set the factor. The house ended up with 0,97 and 0,98 and the garage ended up with 0,81, 0,83 and later 0,89. For the same car, the same afternoon. An 8% difference that cannot be explained by voltage alone.

I don't have room to keep it metered all the time but I can connect it again some day to redo these tests. Both charger numbers are still off compared to the readings from the car. M3, MX and ID3.

Think this afternoon for the M3 the EVCS said 20 and the car only said 18 (with a 0,97 factor)

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Lucian Popescu (Victron Energy Staff) ♦♦ kudos50 commented · Feb 27 at 07:52 PM

Related to the pictures above, this is measured by the meter

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1709063540584.png (58.4 KiB)

Lucian Popescu (Victron Energy Staff) ♦♦ kudos50 commented · Feb 27 at 07:50 PM

EVCS will say a bit more because it measures the AC current. On the Tesla app, you have only the DC energy charged into the battery, not the losses and the energy used for something else like battery heating or sentry etc. But I'm open for tests.

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kudos50 kudos50 commented · Feb 27 at 08:08 PM

Agreed on the Tesla readout. Not much of a fan of the info provided by the VW app either. But that number is because I lost interest after having seen 0.81 - 0.89 on an EATON 3 fase meter in 3 different 10kW charges on the same afternoon.

Harolds story just triggered me. The 20% difference cannot be explained (my 8% cannot be explained either).

I need to completely disconnect the wiring and leave the meter connected in open air. So I need some time and some dry/sunny weather to make that happen. Garage is indoor. Will find some time and figure out a way to get you the data.

If voltage is missing, does my idea to take it from the grid meter / Cerbo improve accuracy ?

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Lucian Popescu (Victron Energy Staff) ♦♦ kudos50 commented · Feb 27 at 09:00 PM

Yes, we can do that if necessary, but first let's have some tests.

On my test system, I don't have any other consumers, just the EVCS and the results are pretty good. Let's see on yours.

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dennibu kudos50 commented · Feb 28 at 05:32 PM

Das Problem ist, dass nicht nur die Höhe der Spannung fehlt, sondern auch die Phasenverschiebung zum Strom. Somit bleibt der Anteil der Blindleistung unberücksichtigt. Die Ladegeräte an den Fahrzeugen haben je nach Ladeleistung wechselnde Blindströme. Daher ist die Höhe der Spannung allein nicht wirksam.

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kudos50 dennibu commented · Feb 28 at 07:09 PM

Are you referring to the power factor ? I thought the powerfactor of an EV charger under load is pretty close to 1 ?

But agreed, if not 1 than voltage alone without phase shift can only contribute so much.

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kudos50 kudos50 commented · Feb 28 at 09:05 AM

Changed power correction back to 1.0 (from 0.89). There's hardly any solar and I found a moment in which all heatpumps are inactive. Please note that the MX also says 11A instead of 12A! Don't think that's the case for the other EVCS. But will recheck this afternoon with the M3.

Everything is wired up with 6mm2 and the charging cable is a 32A (6mm2) cable as well.

On a side note: the connection between house and garage is only 4mm2 over a 50m distance with a 16A breaker. Will need to change that some day. So at the time this foto was taken the 228V at the house only has 224V remaining in the garage if the car is charging.

The difference between the kWh meter phase readout and the multi's critical loads readout makes sense. Phase 3 has close to nothing where 1 and 2 do have a small load. kWh meter is connected only to the EVCS with a 50cm cable.

Also, if you simply stare at the numbers over coffee, the kWh meter and the critical loads numbers vary only 10 to 20W but if you open the webpage for the EVCS the numbers per phase go up and down as much as ~250W (~2600 to ~2900!)

Will punch the numbers once the second charging session completes later today.

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image-28-02-2024-at-0945.jpg (325.8 KiB)

Lucian Popescu (Victron Energy Staff) ♦♦ kudos50 commented · Feb 28 at 09:11 AM

Maybe we can and power calibration in multiple points

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kudos50 kudos50 commented · Feb 28 at 11:51 AM

Jup...setting a calibration below 1 does give a proper readout but in reality the EVCS still says it's 12A whereas all matching readout (including the car) say it's only 11A (in this example 225v x 3 x 11 = 7.4Kw).

Let me first focus on getting the inconsistent results back on screen. This test was 0,853. If I make an educated guess the read of the kWh meter is in line with the VRM readout of the critical loads (it's missing about 150W which is about correct)

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Lucian Popescu (Victron Energy Staff) ♦♦ kudos50 commented · Feb 29 at 04:02 PM

We will add calibration on multiple points, actually we already have it, but there is no GUI for the user to do it.

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kudos50 kudos50 commented · Feb 28 at 03:27 PM

Numbers with M3 are consistent with MX for this test. With calibration set to 1.0 I got 0,853 for the MX and 0,847 for the M3.

Will keep it connected and do it again with the ID3 this evening. From that I will try and change variables like charge current, wait for sun early next week etc etc..

For now not able to reproduce the constantly changing consumption numbers.

However. My MX is solely responsible for the odd charge current. A 12A setting on the EVCS has the following results in the EVCS power readout:

MX: 8400 (x 0,85 = 7140 with 224V = 10,6A = ~11A)

M3: 9500W (x 0,85 = 8075 with 225V = 12A)

I did re-run the CP calibration but the outcome obviously remains unchanged. The MX simply takes less power on the EVCS than it does on Elvi or TWC.

Will report the numbers for the ID3 as well this evening. Could be the 17kW unit from the MX just negotiates differently. I have the raven whereas your screenshot is palladium I think?

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Lucian Popescu (Victron Energy Staff) ♦♦ kudos50 commented · Feb 28 at 04:14 PM

I think there are chargers that are not capable of 1A steps, I remember seeing this on other occasion, so that might be the reason. If you have an oscilloscope you can compare the duty cycle on our charger with the other one. But for 12A, should be the same .

Yes I have an MX Plaid

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kudos50 kudos50 commented · Feb 28 at 08:29 PM

Possibly. But still strange to see 3 different cars charge with 3 different charge currents with the EVCS set to 12A. I made reservations in my flow to only use even number but so far the cars are good with 1A so it's commented out:

MX: 8400 (x 0,85 = 7140 with 224V = 10,6A)

M3: 9500W (x 0,85 = 8075 with 225V = 12A)

ID.3: 8950 (x 0,85 = 7600 with 223V = 11,4A)

Waiting for the session to finish and hope consumption is about 0,85 as well. Probably is as the kWh meter says ~7600 as well.

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kudos50 kudos50 commented · Feb 28 at 09:26 PM

Tests with MX:

1779,042 - 1769,21 = 9,832

Against 11,53 on the EVCS

Factor 0,853

MX reports 9kW added

Test M3:

1779,049 - 1790,667 = 11,618

Against 13,71 on the EVCS

Factor 0,847

M3 reports 11kW added

Test ID3:

1794,018 - 1802,863 = 8,845

Against 10.34 on the EVCS

Factor 0,855

VW app does not report session details

All ~0,85. So not able to reproduce the severe inconsistencies I experienced earlier. Honestly, do not understand why as the methodology was the same.

Will keep the kWh meter connected and vary with charge current over the next week. And now that the EVCS is open anyway, will reconnect the Elvi and try and observe the strange differences in charging current. I do not remember that ever being an issue but than again... I never took a closer look.

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