[EQA-S.oz]

I took delivery of my EQA on 28 April and since then I've recharged the high voltage battery once.

I anticipate that most of my charging will be done at home using the AC current mains charging cable supplied with the car. Our electricity supply contract provides power at three prices, as follows: Peak rate, Off-peak rate and Shoulder rate. Peak rate (6am to 10am, then 3pm to the following 1am) is the most expensive, then Off-peak (1am to 6am) and Shoulder (10am to 3pm) is the cheapest. I aim to charge my car battery at the Shoulder rate, when possible. As I don't use my car every day, there may be times when I charge the car over several days during that 5 hour window.

I think the Owner's Manual leaves a lot to be desired, not least as it relates to charging. It is very thorough as regards safety warnings, but less so as regards helpful information. Mains-supply home charging is one such example. The Manual doesn't, for instance, instruct when to turn the mains supply on and off in the charging sequence. Perhaps that's just too basic? On the single occasion when I charged the battery at home, I made the charging cable connections, then turned the mains power on - and I turned the mains power off before removing the cable. It seemed to work and I'm not aware of having damaged anything.

The purpose of this post is to seek the brains trust's advice as to the advisability of leaving the cable attached to the car in a scenario where I want to charge the battery on say two or three consecutive days (leaving the car in the garage). I would turn the mains power supply to the cable on at 10am and off at 3pm on each of those days - and remove the cable once I've charged the battery to the desired level.

Does anyone know whether it is OK to leave the charging cable connected - and not supplied with mains power during the remaining 19 hours each day - in a scenario such as this?

Needless to say, I don't have a wallbox and so far I haven't used any public charging facility.

 

[dBC]

Yes, that should be fine. The app will display "Charging interrupted" during the blackout periods. I assume the box on your supplied cable says 8A like mine? (see also Home charging won’t exceed 1.7kw on 3 pin.)

I have a 7.5kW EVSE (aka wallbox) and it's on a "controlled load" ripple controller so Energex can remotely turn it on/off as they see fit - which is pretty much the equivalent of what you'll be doing. I often plug it in during the evening OFF period, and then when they decide (around 8pm) it comes to life and I get a notification on the app that charging has commenced. I try to arrange things so that it's not charging at the instant they turn things OFF. Even though the contactor is rated for 40A, I figure it'll last longer if it's not regularly interrupting 32A.

If you're going to regularly charge from a 10A power point, don't ignore the requirement to have it inspected by somebody competent. Prior to EVs, it was pretty unusual for a power point to have to deliver maximum power for hours on end. The power involved is roughly the equivalent of an electric kettle, but they typically only run for a few minutes at a time. A poorly terminated cable at the back of the power point may go unnoticed for years with intermittent use but can turn into a disaster when running continuously (see for example Near miss charging from a 13A household socket.)

 

[dBC]

Peak rate (6am to 10am, then 3pm to the following 1am) is the most expensive, then Off-peak (1am to 6am) and Shoulder (10am to 3pm) is the cheapest.

Are you saying your Shoulder period is cheaper than your Off-peak period? Which state do you live in? It kinda' makes sense that it would be because they often have excess solar energy in the middle of the day, so funneling that into EVs is a good strategy, but I wasn't aware they'd built that into their pricing yet.

 

[EQA-S.oz]

Thank you for your informative reply, dBC - and your notes of caution.

Yes, my supplied cable says 8A and to err on the side of caution, I'm charging the battery at 6 amps.

We live in a newly constructed home and having been intimately involved in its construction, I have quite a good relationship with the electrical contractor. I plan to contact them sometime soon to discuss car charging and pragmatic options.

Responding to your second post; I'm in Adelaide (retailer, AGL). Yes, the Shoulder rate is 3-4 cents per kWh lower than Off-peak, which sounds counter-intuitive until you take into account solar feeds.

 

[dBC]

I'm in Adelaide (retailer, AGL). Yes, the Shoulder rate is 3-4 cents per kWh lower than Off-peak, which sounds counter-intuitive until you take into account solar feeds.

Ahhh right.. you guys are famous for your rooftop PV uptake. I guess it was easier for them change the pricing than change the names. Your charging strategy should ensure your EQA is almost always powered by the sun, regardless of whether you have panels or not.

 

[FDR]

I took delivery of my EQA on 28 April and since then I've recharged the high voltage battery once.

I anticipate that most of my charging will be done at home using the AC current mains charging cable supplied with the car. Our electricity supply contract provides power at three prices, as follows: Peak rate, Off-peak rate and Shoulder rate. Peak rate (6am to 10am, then 3pm to the following 1am) is the most expensive, then Off-peak (1am to 6am) and Shoulder (10am to 3pm) is the cheapest. I aim to charge my car battery at the Shoulder rate, when possible. As I don't use my car every day, there may be times when I charge the car over several days during that 5 hour window.

I think the Owner's Manual leaves a lot to be desired, not least as it relates to charging. It is very thorough as regards safety warnings, but less so as regards helpful information. Mains-supply home charging is one such example. The Manual doesn't, for instance, instruct when to turn the mains supply on and off in the charging sequence. Perhaps that's just too basic? On the single occasion when I charged the battery at home, I made the charging cable connections, then turned the mains power on - and I turned the mains power off before removing the cable. It seemed to work and I'm not aware of having damaged anything.

The purpose of this post is to seek the brains trust's advice as to the advisability of leaving the cable attached to the car in a scenario where I want to charge the battery on say two or three consecutive days (leaving the car in the garage). I would turn the mains power supply to the cable on at 10am and off at 3pm on each of those days - and remove the cable once I've charged the battery to the desired level.

Does anyone know whether it is OK to leave the charging cable connected - and not supplied with mains power during the remaining 19 hours each day - in a scenario such as this?

Needless to say, I don't have a wallbox and so far I haven't used any public charging facility.

I’m not sure if there’s anything in it but there have been lots of discussions on the Speakev forum that suggest it’s better for the car to stop the charge rather than switching off at the socket. It seems the car, or wallbox, shuts down in a controlled way and while the car has something to protect against sudden power interruptions this can be damaged by too many uncontrolled stops.

 

[EQA-S.oz]

Thank you for that insight, FDR. Can you, or someone else, advise the best way to shut down charging "in a controlled way" in a situation where the car is being charged, but won't be driven until sometime later - perhaps, the next day?

Expanding on this discussion; are there settings in the EQA which would allow you to connect the mains charging cable to the car and set a later "start charging" time (and "stop charging" time) before switching the power on at the switch? I ask, because this would seem to be a convenient way to access cheaper electricity rates and possibly to also enable the car to condition itself optimally to accept a charge.

 

[dBC]

advise the best way to shut down charging "in a controlled way"

The only way I know of is to press the Unlock button at the car's charging port. I think the closest the App comes to letting you stop the charging, it to set the target charge level lower than the current level, but that only goes down as low as 50%, so wouldn't help if you needed to stop it charging at say 40%.

set a later "start charging" time (and "stop charging" time)

I can't speak for the EQA but on the EQC they let you set a departure time. I think the theory was the software would then decide when to start charging to ensure it had got to the requested charge level by the specified time. But on the EQC that departure time setting is ignored, and it always starts charging once you plug it in. Rumour has it they couldn't quite nail it, had too many complaints about people waking up to find their car not charged, and so disabled it. Maybe that got fixed on the EQA?

 

[dBC]

better for the car to stop the charge rather than switching off at the socket. It seems the car, or wallbox, shuts down in a controlled way and while the car has something to protect against sudden power interruptions this can be damaged by too many uncontrolled stops.

Do you have a pointer for that? It seems dubious to me, but I'd like to see what their argument is.

There are plenty of reasons why you don't want to interrupt high current circuits without winding them down gracefully first - particularly 300A DC. Even with my 32A AC wallbox, I figure my contactors will last longer if I can arrange things such that charging is finished before Energex turns things off.

But I'm struggling to think of anything inside the car that is going to be stressed by killing the power to a 2kW AC charger - actually closer to 1400 watts given the OP has set it to 6A max.

 

[EQA-S.oz]

The only way I know of is to press the Unlock button at the car's charging port. I think the closest the App comes to letting you stop the charging, it to set the target charge level lower than the current level, but that only goes down as low as 50%, so wouldn't help if you needed to stop it charging at say 40%.


I can't speak for the EQA but on the EQC they let you set a departure time. I think the theory was the software would then decide when to start charging to ensure it had got to the requested charge level by the specified time. But on the EQC that departure time setting is ignored, and it always starts charging once you plug it in. Rumour has it they couldn't quite nail it, had too many complaints about people waking up to find their car not charged, and so disabled it. Maybe that got fixed on the EQA?

Thanks, dBC. I'll try the departure time setting and see whether, in my EQA, it starts charging straight away.

I understand from the Delphi IC-CPD User's Manual which was supplied with my car that you're supposed to plug the cable into your 240v (in Australia) mains power point, then turn the power point ON, then plug the vehicle connector into the car. Is that correct? It seems a bit counter-intuitive to me, but I presume the power feed to the car doesn't begin until the vehicle connector is locked in the car (i.e. the vehicle connector isn't 'hot' when it's inserted into the car receiver; rather, it 'livens up' afterwards). Is that correct?

 

[dBC]

Yep, that's right. They do a little handshake so the car knows how much current it can draw then things get turned on. But I regularly plug my car in to a dead EVSE. The car shows that as connected, but interrupted. Then when Energex turn the power on at about 8pm, the car starts talking to it, and charging commences about 20 seconds later.

 

[dBC]

And there are plenty of folk here who have put timers on their EVSE so as to only supply power to it during their low tariff periods, then plug the car in and go to bed. It comes to life when the timer kicks on at midnight or whatever. That's basically an automated version of what you're proposing to do manually. They needed to do that because the Departure Time feature doesn't work.

 

[FDR]

Do you have a pointer for that? It seems dubious to me, but I'd like to see what their argument is.

There are plenty of reasons why you don't want to interrupt high current circuits without winding them down gracefully first - particularly 300A DC. Even with my 32A AC wallbox, I figure my contactors will last longer if I can arrange things such that charging is finished before Energex turns things off.

But I'm struggling to think of anything inside the car that is going to be stressed by killing the power to a 2kW AC charger - actually closer to 1400 watts given the OP has set it to 6A max.

I’m not an expert but several posts have been on Speakev.com about this, (Installing a timer for my charge point , advice please) mostly for wall boxes and as you say it may not be as important with lower power plug-in charge point.

 

[FDR]

Post #20 gives the best explanation

 

[dBC]

Yeh, I don't see anything in there that suggests repeated blackouts will damage the car though. All it's saying is that charging may not recommence when power returns... apparently once a problem in Model 3s, i.e. you'd need to remove and re-insert the plug to get charging to continue. That's not a problem on EQs, and I suspect has been fixed on Teslas too.

 

[FDR]

Yeh, I don't see anything in there that suggests repeated blackouts will damage the car though. All it's saying is that charging may not recommence when power returns... apparently once a problem in Model 3s, i.e. you'd need to remove and re-insert the plug to get charging to continue. That's not a problem on EQs, and I suspect has been fixed on Teslas too.

I think the point is that the car needs time to get ready to charge and to reduce the current before it stops charging. The thing that occurred to me on reading this and other threads on the subject is that an EV is in many respects a computer on wheels and I don’t think it’s a good idea to switch off a PC by pulling out the plug rather than shutting it down correctly.

 

[dBC]

We're not talking about killing power to any of the car's computers.. they're all powered by the car. We're discussing killing the power to the car's on-board AC charger. If you can identify which components in the car you think that stresses, we can discuss it, but I can't think of a single one.

The reason for the orderly shutdown is to prolong the life of the contactors (primarily the ones in the EVSE) by not having them open while large currents are flowing. That's for the more common case where the power hasn't failed. If the power has gone away then so have the large currents. I can count tens of seconds between me killing the supply to the EVSE and car eventually giving up on it and opening its contactors, so any currents that were flowing are long gone.

I think the car has been designed to be completely resilient to power failures during AC charging cycles, even daily ones caused by upstream timers. The app even has a name for the state it's in while sitting around waiting for the power to come back - "Interrupted".

 

[FDR]

I’m not equipped to discuss this in detail, I’m a farmer not an electrical engineer, I just thought it was worth drawing attention to what people who are electrical engineers have said on the matter. As I said at the beginning there may be nothing in it. These people may be experts in electrics but not in Mercedes EQAs and the definitive answer to the question can only come from Mercedes. It used to be these sort of questions could be answered by a dealer or if they didn’t know they would ask the manufacturer. Good luck with that nowadays!!