RoadTest: Product Review of the Megger EV Charger Checker – EVCC300
Author: Fred27
Creation date:
Evaluation Type: Connectors & Cable
Did you receive all parts the manufacturer stated would be included in the package?: True
What other parts do you consider comparable to this product?: Megger also supply the MFT1741+ which is designed for verifying an installation and an EVCA210 which also performs a different role. I'm not sure there is a direct equivalent to the EVCC300.
What were the biggest problems encountered?: Quirk with the "press for 2s" back button and lack of printed documentation.
Detailed Review:
So, a cardboard box turned up all the way from the Element14 head office in Chicago. Inside this very well protected package was a nice sturdy carry case containing the EVCC300 and its accessories. This injection moulded case is designed to be taken out on site for the checking EVSEs, so it looked tough enough to have been survived the journey unprotected. I also found it a little ironic that whilst the package had flown the thousands of miles to get here, it was made by Megger here in the UK not too many miles from me.
Anyway, opening the case revealed
You might notice that I keep referring to what's frequently called a "EV charger" as an EVSE. I'll continue to do this as Electric Vehicle Supply Equipment is the correct term. The chunky wall-mounted box or "granny cable" that is often referred to as a charger is nothing of the sort. There's no rectification going on. There's no monitoring of battery voltage to determine state of charge. With the type of AC "charger" we'll be using there's no charging going on. It's essentially a couple of large contactors that - if the conditions are right - will connect your building's AC mains to the vehicle.
In the UK where I'll be performing my tests, some commercial EVSEs are capable of supplying 415V 3-phase AC, but the domestic chargers that the EVCC300 is designed for operate on 240V single-phase AC. In the US, 120V single phase and 240V 2-phase are apparently supported.
My initial assumption when I saw the EVCC300 come up for RoadTesting was that it was for checking that a EVSE had been installed correctly and is safe. It seems that this isn't quite correct. However, I'm not the only one to be a little confused by this. A short video from a Megger employee clarifies this.
The EVCC300 is intended for checking and diagnosing problems with an EVSE. It's not intended for verifying an installation or ensuring safety. If you're a professional installer then the MFT1471+ is for you (at a rather heftier price). The simpler EVCA210 looks to be designed as an adapter for letting you connect other test equipment and to simulate the required Proximity Pilot and Control Pilot states.
I hope this makes it a little clearer. I think I get the subtleties, but will probably still use the EVCC300 to help give me some confidence in my secondary installation.
The Quick Start guide had only one useful page of information, with a pictorial description of how to power on, select a language and the the VTOUCH and VMAINS voltages. It missed out one of the required steps which is to select whether you're using the device via a cable or directly connected to the EVSE. (This is important as the cable contains a resistor to tell the EVSE what current it is capable of handling. To be honest steps 5 - 8 were not really very clear. After using the device I now know it's telling you how to select a test and that for one test you need to touch the pad before pressing the red button. It wasn't obvious before though. I'm not sure the Quick start guide is really worth bothering with. I've included the only useful page here.
There is however a far more useful User Guide that you can view on line. This comes in at 46 pages as opposed to the Quick Start's (mostly legalese) 12 pages, but I think it would have been worth including it - especially as this device is intended to be used onsite where it might not be that easy to download and view a PDF.
There is also a nice video provided by Megger on YouTube that does a good job of running through the initial setup.
The EVCC300 has a nice 320 x 240 colour screen. (It's made in the UK, so this is the correct spelling of colour. 
) It seems nice and bright when indoors or outside on a cloudy day. but I did find it washed out a bit in the sunshine. (What do you mean? Of course we get that here.) In particular I found that the icon showing whether you were in cable or non-cable mode was difficult to see in sunlight. The settings that at entered when you first start up are retained once the device is power off which is useful.
My main EVSE is a Easee One that's been professionally installed on the wall of my house. However, I will soon be installing a second Easee One myself. This will all be wired to UK standards and the two negotiate how much current to draw between themselves so it will be perfectly safe. However, it does mean that I have a convenient EVSE just connected to a mains plug on my desk to make testing easier. Obviously this setup would not be suitable for providing the sort of current to charge a vehicle, but fine for some testing.
There are a number of tests that the EVCC300 can perform. I'll start by running through each of these in turn using the Easee One on my desk. The User Guide states that these test should be run in order - mainly as the first ones are for what could be potentially dangerous defects or misconfiguration.
This test checks that there is a Protective Earth connection to the charger. The instructions state that you are required to hold a finger on the PE touch pad and press the test button. There is some audible clicking of relays inside the device and (provided you have a protective earth) after about 10s the reassuring "proceed" message comes up. I also tried this test with the device not connected to the EVSE and as you might expect, this shows a fault due to the missing earth connection. If this were to happen when connected to the EVSE, it would be sensible to abandon further checks, disconnect it and call a qualified electrician.
According to the manual, an open circuit (over 600kOhm) will trigger this fault, as will the earth being shorted to Live. A short to Neutral will apparently not be detected.
This check measures continuity between the Protective Earth and any exposed metal on the EVSE. This is the only test that requires the lead with the ground clip (or probe contact) to be connected to the 4mm socket on the base of the device. As my device does not have any exposed metal I can't perform this test. However, the guide shows it be a simple resistance measure between the PE and whatever the lead is connected to. Anything over 0.5 ohm is a fail.
This is a further safety check. It involves ensuring that the Residual Current Device (RCD) or Ground Fault Circuit Interrupter (GFCI) will switch off the mains supply if leakage is detected. For the UK and Europe, 30mA of AC leakage or 6mA of DC leakage should cause the protection circuit to trip. I was considering performing these check on my desk-mounted EVSE, but decided agianst it for a couple of reasons.
I decided that this test should be performed on my professionally installed external device, and that was probably the right call.
My first test was to check what happens with 30mA AC leakage - both at 0 and 180 degree phase. As you can see from the device screen, it successfully killed the power within 9ms. It was however, the external RCD that tripped. If I'd done this inside my family would probably now be shouting that the TV had gone off!
Everything is safe, but I wonder whether the EVSE's internal RCD would have tripped a little later or if this could have been an issue. I don't think it would be wise to try it on the device without the external RCD, but I'm happy that my professionally fitted device is working OK.
I then moved on to testing +6mA and -6mA DC in the same way. These also tripped - but they took about 900ms (still a pass) and were handled by the internal RCD.
Once you're happy that the device is providing adequate protection, the EVCC300 will also allow you to determine exactly how much leakage current will cause a trip. If this is too low then there's a chance that you might get "nuisance" trips when it wasn't really necessary to cut the power. This fits nicely with the purpose of the device which is for checking the operation of an EVSE rather than certifying its safety.
I once again made sure I was testing my externally wired EVSE with a separate RCD and ran the nuisance checks. These are run in a similar way to the protection checks. You select AC (either 0 or 180 degrees) or DC (positive or negative) rather than using a fixed current and seeing how long it takes to trip, the EVCC300 gradually increases the current and determines what level it trips at.
I'm glad to say that my Easee One does indeed trip when there's some AC leakage. According to my measurements it's a 24mA. This is a reasonable level of protection. It just doesn't trip as quickly as the external RCD. This gets an orange question mark from the EVCC300, so is perhaps considered a bit lower than ideal. The guide states 2mA -14mA as "fail", 16mA - 24mA as "questionable" and 26mA - 30mA as "pass", As I have never had a nuisance trip, I'm happy with the 24mA
On the DC side, the reading is >3mA which is a pass.
The next check in the sequence is to look at how the charger handles being physically connected to a EV and its on-board charger. When this happens, the EVSE should lock any detachable cable and the vehicle should disable driving. You really don't want to be able to drive away with the cable attached!
After you plug the device and and select the EVSE interface tests, pressing the TEST button simulates the "A" state - disconnected. I was testing the EVCC300 without a separate Type 2 cable, so the screen shows that a simulated cable has been connected to the EVSE, but no vehicle yet.
Here I found that my experience differed from the User Guide. The user guide shows a padlock symbol to indicate whether the latch that prevents the cable from being removed was in operation. However, it seems that this does not seem to apply if you're connecting directly without a cable.
The EVCC300 showed some warnings for the measurement from my device. The Neutral in particular seems to be sitting at 15V in the A and B states. This 15V on Neutral also happened on both my Easee One devices but not with a Tesla mobile connector I checked later, so it does seem to be a feature of the Easee One rather than a wiring problem.
We then move onto what's called the control pilot and charger check. This sounds a bit complicated, but really just mimics the communication between the vehicle and the EVSE to see how the EVSE is responding to the various state that the setup can be in. These are:
| A | Disconnected |
| B | Connected |
| C | Charging |
| D | Charging with ventilation |
| E | CP to PE fault |
| F | Charger fault |
In each of these state the EVCC300 displays the voltages detected, the mains frequency, the current rating of the cable, the voltage, duty cycle and frequency of the Control Pilot signal, and the current state. Against each, a helpful symbol shows whether this is as expected. This would help you determine for instance if the Control Pilot signal is an out-of-spec voltage or frequency and perhaps disrupting communication.
Here you can see how my Easee One performed in these states.
Once you're familiar with all the available tests, you can also set the EVCC300 up to automatically perform the ones you want in sequence. I can imagine this is really useful if you have a bank of EVSEs at a commerical charging station or an office block and want to verify that they're all working as expected. The device is marketed as suitable for this sort of use case rather than a tool for installers.
So, my primary testing was carried out using an Easee One mode 3 wall-mounted EVSE - also simulating the cable that connects to the device. I wanted to check a number of mode 2 EVSEs too. A mode 2 EVSE is often referred to as a "granny cable". In the UK these are limited to about 3kW as opposed to the 7kW of the type 3 EVSEs, and they can be connected to a normal 31A 240V outlet to charge your vehicle somewhere that a type 3 device isn't available.
The first mode 2 device I tested was an old Nissan EVSE. To be honest I'd changed the EU plug for a UK one and carefully re-inserted the NTC thermistor from the moulded EU plug so it still had protection from the plug overheating. You shouldn't really do this, but at the time I'd just got my new Zero SR/F electric motorbike and didn't have a mode 3 EVSE installed yet. It did the job and seemed to work safely enough.
However, the EVCC300 wasn't so sure. I made sure I switch the tester to "cable mode" and started to perform the same tests I did with the Easee One. It failed on the first PE check! You're advised from this point to stop any further checks as the protective earth may hot be safe. Whilst I have used this device without incident, this is perhaps a sign that it should be retired from active service - especially as I have a mode 3 wall-mounted EVSE now and don't need it.
My wife recently got a Tesla Model 3, and these come with their own "Tesla Mobile Connector" - i.e. granny charger cable. I decide to check this in the same way. It could of course be the outlet I used that had a fault rather than the EVSE.
Results with the Tesla device were much better. It performed much as the Easee One did. In fact some of the figures such as the mains voltage in the B state looked better.
The EVCC300 is a really useful tool when investigating an EVSE. It gave me a better understanding of what's going on with the devices I checked, It should definitely be considered a diagnostic tool rather than something to verify an installation though. I can imagine it would be easy to be confused as to its purpose and the fact that a Megger employee created a video to highlight this reinforces this view. If you understand what it's for and decide it's what you need then I can recommend it.
Whilst the EVCC300 was generally easy to use, however I did trip up when first using it. The "back" button displays "BACK 2s" so to go back I pressed it in and held it. After about 2s I was rewarded with a beep and nothing else happening. Pressing it briefly didn't seem to do anything either. It seemed to be stuck and all I could do was to turn the device off and on again. I thought I'd discovered a bug, but it turns out the answer is a bit simpler, if a little annoying. You have to press it for just the right amount of time. Then it'll go back. Too short - no. Too long - no. It has to be in the 2s ballpark. It's not a huge deal when you know and I can mostly time it correctly, but usability-wise it's pretty bad.
My device has firmware v1.18 but no firmware version is shown in the guide, and I can't be sure whether my firmware is newer or older. I can't see any way to download and install new firmware to the EVCC300 anyway. The guide was written in 2022 but was downloaded directly from the Megger website. The device was sent to me by Element14 recently. I'm not sure which is later. I tried to check with Megger via the contact form on their website, but so far have not received a reply from them.
